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Posted: 5/18/2015 3:37:40 PM EDT
[#1]
Quote HistoryQuoted:
Now, if you had instead asked about a spaceship traveling at the speed of light turning on its headlights, that would have been an interesting question. An even better question is why does a spaceship need headlights? |
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Posted: 5/18/2015 3:40:02 PM EDT
[#2]
Quote HistoryQuoted:
You're either trolling or retarded. Quote HistoryQuoted:
Quoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to cannon being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. You're either trolling or retarded. Maybe retarded. |
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Posted: 5/18/2015 3:43:14 PM EDT
[#3]
Quote HistoryQuoted:
Briefly. Once it leaves the barrel, it will slow dramatically. In a test in the early supersonic era, a fighter shot itself down when it flew into the slowing projectiles at supersonic speed. TC Quote HistoryQuoted:
Quoted:
It will go at the speed of the projectile plus the speed of the plane. Briefly. Once it leaves the barrel, it will slow dramatically. In a test in the early supersonic era, a fighter shot itself down when it flew into the slowing projectiles at supersonic speed. TC While in a 20° dive and 11 seconds after firing. It's not like he just ran into his bullets right afterwards. |
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Posted: 5/18/2015 3:44:08 PM EDT
[#4]
Quote HistoryQuoted:
Fighter jet @ 2,000fps + Bullet out the barrel @ 2,000fps = Bullet going 4,000fps Quote HistoryQuoted:
Quoted:
Dang, all these answers and only two of them serious! So all you physics experts that think I am stupid, can you dumb it down just a LITTLE bit to explain what will happen? Fighter jet @ 2,000fps + Bullet out the barrel @ 2,000fps = Bullet going 4,000fps Let's give you a visual reference. Rent/download/steal the move Stealth starring Jessica Biel and some other dudes. Roughly 1/3 into the movie, they want to bomb a city building full of terrorizers but the concrete pad on roof is too substantial for effective penetration of their truncheon bomb (or something about civilian casualties but thats not plausible). So How do they solve the problem? SCIENCE, duh.....so the guy who gets to bang jessica biel does a nose dive from high altitude and at maximum terminal velocity releases said truncheon bomb. result? total devastation of target, mission success, rogue badass uses science to win the right to take Jessica Biel to pound town. as a bonus, you can continue to watch and see jessica biel be chased by North Korean dog soldiers.... |
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Posted: 5/18/2015 3:45:11 PM EDT
[#5]
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Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. |
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Posted: 5/18/2015 3:45:32 PM EDT
[#6]
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NO There is this thing called gravity. It is going to suck the bullet toward the ground. The plane has a thing called lift. In level flight the plane is not moving toward the center of the earth. The bullet is. BULLETS do no normally experience lift, despite what you may think. Quote HistoryQuoted:
Quoted:
Velocity of Plane (1100 fps) + Velocity of Bullet at muzzle (3000 fps)= 4100 fps (speed of bullet for one split second till aerodynamics take over). Immediately leaving the barrel the bullet will be going fast, but losing velocity as soon as it leaves the barrel. Since the plane has the power to keep it's speed the plane will catch the bullet eventually. So, yes a plane can shoot itself down if it comes into the path of it's own bullets. Ground observer will see bullet going 4100 fps and the plane will see it going 3000 fps. NO There is this thing called gravity. It is going to suck the bullet toward the ground. The plane has a thing called lift. In level flight the plane is not moving toward the center of the earth. The bullet is. BULLETS do no normally experience lift, despite what you may think. Damn man I know that. I know bullets don't have lift either. It starts dropping the split second it leaves the barrel. Notice I said if it comes into the path of the bullets. Meaning that the plane would need to angle down after firing to really run into it's own bullets. I'm trying to make it as simple as possible since there are clearly people in this thread that still don't get it. Physics and GD aren't a match for each other. 
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Posted: 5/18/2015 3:55:07 PM EDT
[#7]
Physics and GD aren't a match for each other
Or, Newton wept. There are a lot of people here that failed high school physics. |
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Posted: 5/18/2015 3:58:01 PM EDT
[#8]
Quote HistoryQuoted:
Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. Quote HistoryQuoted:
Quoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from your fingers. |
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Posted: 5/18/2015 4:02:38 PM EDT
[#9]
Quote HistoryQuoted: Maybe retarded. Quote HistoryQuoted: Quoted: Quoted: Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to cannon being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. You're either trolling or retarded. Maybe retarded. The ball bearing you hold out the window already shares a 10mph velocity because of the car. That velocity was imparted on the ball bearing when the car sped up to the current speed. Now if you drop it, at that exact instant it has a 10mph velocity relative to the ground until other forces like wind resistance begin to slow it down. Let's say for the sake of argument if you were sitting in a stationary car and could throw the ball forward while leaning out the window with a velocity of 10mph. Now the car gets up to 10mph, you lean out the window and give it your 10mph pitch forward, the ball bearing will actually move ahead of the car. The only way the ball bearing can move ahead of the car is if it has a greater velocity than the car. If the car is going 10mph and the ball bearing is moving faster than the car, then the velocity of the ball is obviously greater than 10mph. What happens is, to you the observer in the car, the ball moves away from you at the same rate it did when the car was sitting still. To an observer on the sidewalk, the ball is moving forward at a rate of 20mph because the car was moving 10mph, and you added another 10mph to the ball. |
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Posted: 5/18/2015 4:03:01 PM EDT
[#10]
Quote HistoryQuoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to connons being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. yes it is. your hand and the ball bearing are moving at 10mph before you let go. Or are you saying the instant you let go, the horizontal speed is zero and the bearing hits the ground with zero forward speed? |
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Posted: 5/18/2015 4:03:49 PM EDT
[#11]
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It does make one wonder how waist gunners ever hit anything. Perhaps at the relatively slow speed of a bomber the bullet isnt greatly affected by the lateral drag? (I.e., the bullet has the velocity of the bomber, but it's sideways to the bullet., our bullet is travelling 2800 fps away from the plane but it also has a roughly 400 fps sideways component) they learned how to lead. Tracers help visualize what was going on. |
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Posted: 5/18/2015 4:05:44 PM EDT
[#12]
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That may be true however most of you who THINK you have it figured out are also forgetting something very important. What altitude is this supersonic aircraft at? At sea level is vastly different than 35,000'. That will have a huge effect on the drag force experienced by the projective. And, no matter what anyone says, the bullets will start to drop away from the aircraft's line of travel as soon as they leave the barrel. They will accelerate towards the earth's center at 9.80655 m/s^2. The plane, assuming level flight, is not. You can't run into your own bullets unless you yourself are in a dive. um, wrong. I can be in level flight with a nose up or a nose down attitude. I can fire slightly up and run into the rounds as they descend through the flightpath from above. you also fail to take into account how the barrel of the gun is aligned with the aircraft. The aiming reticle matches the cannon - for air to air. you need a different reticle for air to ground.... |
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Posted: 5/18/2015 4:05:48 PM EDT
[#13]
Quote HistoryOriginally Posted By waterglass: My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from you fingers. Quote HistoryOriginally Posted By waterglass: Originally Posted By djkest: Originally Posted By waterglass: Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from you fingers.  |
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Posted: 5/18/2015 4:09:24 PM EDT
[#14]
Quote HistoryQuoted: My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from your fingers. Quote HistoryQuoted: Quoted: Quoted: Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from your fingers. Gravity has no effect on forward velocity, just the time it takes for the projectile to strike the ground. In other words, gravity does not slow the forward movement of an object. Here's a question for you, if you fired a subsonic 9mm round forward from an airplane flying at supersonic speed, what would the effect be on the bullet? |
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Posted: 5/18/2015 4:09:56 PM EDT
[#15]
Quote HistoryQuoted:
yes it is. your hand and the ball bearing are moving at 10mph before you let go. Or are you saying the instant you let go, the horizontal speed is zero and the bearing hits the ground with zero forward speed? Quote HistoryQuoted:
Quoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to connons being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. yes it is. your hand and the ball bearing are moving at 10mph before you let go. Or are you saying the instant you let go, the horizontal speed is zero and the bearing hits the ground with zero forward speed? I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. |
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Posted: 5/18/2015 4:14:20 PM EDT
[#16]
Quote HistoryQuoted:
My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from your fingers. Quote HistoryQuoted:
Quoted:
Quoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from your fingers. A bullet fired from a gun perfectly level and one dropped from the same height as the barrel at exactly the same time will impact the ground at the same time. |
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Posted: 5/18/2015 4:16:03 PM EDT
[#17]
Quote HistoryQuoted:
Gravity has no effect on forward velocity, just the time it takes for the projectile to strike the ground. In other words, gravity does not slow the forward movement of an object. Here's a question for you, if you fired a subsonic 9mm round forward from an airplane flying at supersonic speed, what would the effect be on the bullet? Quote HistoryQuoted:
Quoted:
Quoted:
Quoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from your fingers. Gravity has no effect on forward velocity, just the time it takes for the projectile to strike the ground. In other words, gravity does not slow the forward movement of an object. Here's a question for you, if you fired a subsonic 9mm round forward from an airplane flying at supersonic speed, what would the effect be on the bullet? The same thing that would happen if you threw a golf ball straight ahead of you at a velocity of 10MPH while traveling at 70MPH. |
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Posted: 5/18/2015 4:16:39 PM EDT
[#18]
Quote HistoryOriginally Posted By waterglass: I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. Quote HistoryOriginally Posted By waterglass: Originally Posted By dorobuta: Originally Posted By waterglass: Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to connons being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. yes it is. your hand and the ball bearing are moving at 10mph before you let go. Or are you saying the instant you let go, the horizontal speed is zero and the bearing hits the ground with zero forward speed? I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. |
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Posted: 5/18/2015 4:16:48 PM EDT
[#19]
Quote HistoryQuoted:
I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. Quote HistoryQuoted:
Quoted:
Quoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to connons being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. yes it is. your hand and the ball bearing are moving at 10mph before you let go. Or are you saying the instant you let go, the horizontal speed is zero and the bearing hits the ground with zero forward speed? I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. it will slow down according to the coefficient of drag. EVERYBODY is saying this. IT WILL SLOW DOWN. It will still have forward speed because the forward velocity will not have bled to zero before reaching the ground. it is not totally at the mercy of gravity. Gravity is imparting a downward acceleration, but it is the drag that will determine how much forward velocity it will lose before hitting the ground. There's a lot more at work than just gravity. |
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Posted: 5/18/2015 4:17:37 PM EDT
[#20]
Quoted:
This question that has been tickling my brain. I'm sure it never happens, but what if a fighter fired its gun at speeds above Mach? Would the projectiles be Mach plus their normal speed??? Would the projectiles just fall out of the barrel and keep pace with the plane? Could a plane shoot itself down? I have read that the B-58 had its rear firing cannon removed because it could fly faster than the projectiles it fired could leave the barrel. What say the collective GD mind? Initially, the velocity of the platform plus the velocity of the projectile...but that projectile obviously slows down immediately once it leaves the barrel. |
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Posted: 5/18/2015 4:18:30 PM EDT
[#22]
Quote HistoryQuoted: The same thing that would happen if you threw a golf ball straight ahead of you at a velocity of 10MPH while traveling at 70MPH. Quote HistoryQuoted: Quoted: Quoted: Quoted: Quoted: Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from your fingers. Gravity has no effect on forward velocity, just the time it takes for the projectile to strike the ground. In other words, gravity does not slow the forward movement of an object. Here's a question for you, if you fired a subsonic 9mm round forward from an airplane flying at supersonic speed, what would the effect be on the bullet? The same thing that would happen if you threw a golf ball straight ahead of you at a velocity of 10MPH while traveling at 70MPH. And what happens? |
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Posted: 5/18/2015 4:19:20 PM EDT
[#23]
Quote HistoryQuoted:
An even better question is why does a spaceship need headlights? Quote HistoryQuoted:
Quoted:
Now, if you had instead asked about a spaceship traveling at the speed of light turning on its headlights, that would have been an interesting question. An even better question is why does a spaceship need headlights? Duh it's dark in space!
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Posted: 5/18/2015 4:19:29 PM EDT
[#24]
My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. Gravity has nothing to do with it. Gravitational forces are orthoganal to the initial trajectory. If you had a tube through the bottom of an airplane and were flying perfectly parallel to the ground, so the tube was perfectly square to the ground. Now we're flying at 10,000 ft at 600 mph. There is a big target on the ground, if the plane imparts no velocity on a projectile then you should be able to drop an object through said tube the instant the tube was directly over the target and centerpunch the target. Except it doesnt work that way, the object has the initial velocity of the plane, you have to release the bomb, er object, well before the tube is pointing at the target. |
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Posted: 5/18/2015 4:19:46 PM EDT
[#25]
Quote HistoryQuoted:
And what happens? You catch up with the ball as it looses forward momentum. |
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Posted: 5/18/2015 4:24:22 PM EDT
[#26]
Quote HistoryQuoted: You catch up with the ball as it looses forward momentum. Quote HistoryQuoted: Quoted: And what happens? You catch up with the ball as it looses forward momentum. What is the velocity of the ball the instant it leaves your hand? |
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Posted: 5/18/2015 4:25:49 PM EDT
[#27]
it will go in reverse.
Is it on a treadmill? |
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Posted: 5/18/2015 4:27:32 PM EDT
[#28]
Quote HistoryQuoted:
I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. Quote HistoryQuoted:
Quoted:
Quoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to connons being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. yes it is. your hand and the ball bearing are moving at 10mph before you let go. Or are you saying the instant you let go, the horizontal speed is zero and the bearing hits the ground with zero forward speed? I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. The ball is moving forward at a velocity of 4.4 m/s and accelerating downward at 9.8 m/s^2. If you the ball from outside the car with a slow motion camera it would move in an arc. 
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Posted: 5/18/2015 4:38:09 PM EDT
[#29]
Quote HistoryQuoted:
What is the velocity of the ball the instant it leaves your hand? Quote HistoryQuoted:
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And what happens? You catch up with the ball as it looses forward momentum. What is the velocity of the ball the instant it leaves your hand? 80MPH. Or 10 MPH. it is relative. |
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Posted: 5/18/2015 4:44:56 PM EDT
[#30]
Quote HistoryQuoted:
Fighter jet @ 2,000fps + Bullet out the barrel @ 2,000fps = Bullet going 4,000fps Quote HistoryQuoted:
Quoted:
Dang, all these answers and only two of them serious! So all you physics experts that think I am stupid, can you dumb it down just a LITTLE bit to explain what will happen? Fighter jet @ 2,000fps + Bullet out the barrel @ 2,000fps = Bullet going 4,000fps Not if you fire it backwards. |
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Posted: 5/18/2015 4:47:25 PM EDT
[#31]
Quote HistoryQuoted:
I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. Quote HistoryQuoted:
Quoted:
Quoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to connons being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. yes it is. your hand and the ball bearing are moving at 10mph before you let go. Or are you saying the instant you let go, the horizontal speed is zero and the bearing hits the ground with zero forward speed? I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. nope--it still retains momentum from its 10mph initial state, which is why it will describe a parabolic trajectory for a while, before going terminal (falling straight down). if it were completely at the mercy of gravity, it would fall vertically from your hand and not bounce/roll forward when it touched the ground. |
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Posted: 5/18/2015 4:49:40 PM EDT
[#32]
Quote HistoryOriginally Posted By brickeyee: Not if you fire it backwards. Quote HistoryOriginally Posted By brickeyee: Quoted: Quoted: Dang, all these answers and only two of them serious! So all you physics experts that think I am stupid, can you dumb it down just a LITTLE bit to explain what will happen? Fighter jet @ 2,000fps + Bullet out the barrel @ 2,000fps = Bullet going 4,000fps Not if you fire it backwards. |
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Posted: 5/18/2015 4:54:41 PM EDT
[#33]
An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
This law is often called "the law of inertia". 
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Posted: 5/18/2015 5:00:10 PM EDT
[#34]
Quote HistoryQuoted:
I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. Quote HistoryQuoted:
Quoted:
Quoted:
Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to connons being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. yes it is. your hand and the ball bearing are moving at 10mph before you let go. Or are you saying the instant you let go, the horizontal speed is zero and the bearing hits the ground with zero forward speed? I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. The instant it is released, assuming a clean or neutral release, it has a velocity in the X direction of 10 mph (assuming x is aligned with the direction of travel) and 0 velocity in Y and Z directions. However, now the forces acting on it are twofold. Gravity is pulling it down, and drag is opposing any velocity it has. It does retain or maintain it's momentum from the previous instant before it was released. You can't magically remove all momentum instantaneously. |
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Posted: 5/18/2015 5:03:03 PM EDT
[#35]
Quote HistoryQuoted:
An even better question is why does a spaceship need headlights? Quote HistoryQuoted:
Quoted:
Now, if you had instead asked about a spaceship traveling at the speed of light turning on its headlights, that would have been an interesting question. An even better question is why does a spaceship need headlights? DOT requirements. |
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Posted: 5/18/2015 5:04:04 PM EDT
[#36]
Quote HistoryQuoted:
um, wrong. I can be in level flight with a nose up or a nose down attitude. I can fire slightly up and run into the rounds as they descend through the flightpath from above. you also fail to take into account how the barrel of the gun is aligned with the aircraft. The aiming reticle matches the cannon - for air to air. you need a different reticle for air to ground.... Quote HistoryQuoted:
Quoted:
That may be true however most of you who THINK you have it figured out are also forgetting something very important. What altitude is this supersonic aircraft at? At sea level is vastly different than 35,000'. That will have a huge effect on the drag force experienced by the projective. And, no matter what anyone says, the bullets will start to drop away from the aircraft's line of travel as soon as they leave the barrel. They will accelerate towards the earth's center at 9.80655 m/s^2. The plane, assuming level flight, is not. You can't run into your own bullets unless you yourself are in a dive. um, wrong. I can be in level flight with a nose up or a nose down attitude. I can fire slightly up and run into the rounds as they descend through the flightpath from above. you also fail to take into account how the barrel of the gun is aligned with the aircraft. The aiming reticle matches the cannon - for air to air. you need a different reticle for air to ground.... You are of course absolutely correct. But you are complicating the issue beyond the original question. I did mention in a previous post that the barrel should be co-incident with the velocity vector. I guess I should have recognized that level flight does not always mean AOA = 0. |
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Posted: 5/18/2015 5:07:14 PM EDT
[#37]
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Gravity has no effect on forward velocity, just the time it takes for the projectile to strike the ground. In other words, gravity does not slow the forward movement of an object. Here's a question for you, if you fired a subsonic 9mm round forward from an airplane flying at supersonic speed, what would the effect be on the bullet? Quote HistoryQuoted:
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Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from your fingers. Gravity has no effect on forward velocity, just the time it takes for the projectile to strike the ground. In other words, gravity does not slow the forward movement of an object. Here's a question for you, if you fired a subsonic 9mm round forward from an airplane flying at supersonic speed, what would the effect be on the bullet? Obviously the 9mm bullet would go backwards in the gun since it's going slower than the plane, and your receiver would explode in your face and probably kill you. Because of this and the Earth's rotation, you need to make sure you fire any guns only when facing west. |
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Posted: 5/18/2015 5:12:33 PM EDT
[#38]
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The instant it is released, assuming a clean or neutral release, it has a velocity in the X direction of 10 mph (assuming x is aligned with the direction of travel) and 0 velocity in Y and Z directions. However, now the forces acting on it are twofold. Gravity is pulling it down, and drag is opposing any velocity it has. It does retain or maintain it's momentum from the previous instant before it was released. You can't magically remove all momentum instantaneously. Quote HistoryQuoted:
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Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. The principal applies to connons being fired on a plane. If the plane s traveling faster then the projectiles at the muzzle, the bullets will simply exit the barrel and either hit the plane or fall away. yes it is. your hand and the ball bearing are moving at 10mph before you let go. Or are you saying the instant you let go, the horizontal speed is zero and the bearing hits the ground with zero forward speed? I am saying the ball will not retain the 10MPH forward speed or momentum from the car once dropped. It is completely at the mercy of gravity once it leaves your hand. The instant it is released, assuming a clean or neutral release, it has a velocity in the X direction of 10 mph (assuming x is aligned with the direction of travel) and 0 velocity in Y and Z directions. However, now the forces acting on it are twofold. Gravity is pulling it down, and drag is opposing any velocity it has. It does retain or maintain it's momentum from the previous instant before it was released. You can't magically remove all momentum instantaneously. That is more or less my point. My point is that its momentum and trajectory almost instantly degrades due natural forces acting against it. the plane/vehicle won't/ |
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Posted: 5/18/2015 5:13:49 PM EDT
[#39]
Relative Motion, GAWD DAMNIT
Where's that Black Teacher who was whipping his class with a belt when you need him?! |
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Posted: 5/18/2015 5:19:30 PM EDT
[#40]
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Thou shalt not add thy velocity to the speed of light. Same principle applies here. No. Conservation of momentum applies here. Relativity definitely does not. Relativistic effects are negligible in this scenario. The projectile leaves at the speed of the plane + it's muzzle velocity relative to the plane. It will also slow down much more quickly because it has much higher drag forces acting on it due to the higher initial speed. |
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Posted: 5/18/2015 5:19:53 PM EDT
[#41]
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Obviously the 9mm bullet would go backwards in the gun since it's going slower than the plane, and your receiver would explode in your face and probably kill you. Because of this and the Earth's rotation, you need to make sure you fire any guns only when facing west. Quote HistoryQuoted:
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Go drive down the road at 10MPH and drop a ball bearing out the window. the velocity of the car is not imparted on the thing you drop. Actually it is. This is a very easy phenominon to figure out. How do you think a baseball pitcher works? His arm reaches 90 or 100 mph, and then he releases the ball. The velocity of his arm which held the ball is imparted on the object he lets go of. My point was that once it is released it will never retain the speed at which it was dropped. It will have some degree of foward momentum as it falls because gravity is a "weak" force. the same goes for bullets fired from cannon on board a plane traveling faster then the muzzle velocity of the projectiles except they have the much greater momentum of being fired from a cannon instead of being dropped from your fingers. Gravity has no effect on forward velocity, just the time it takes for the projectile to strike the ground. In other words, gravity does not slow the forward movement of an object. Here's a question for you, if you fired a subsonic 9mm round forward from an airplane flying at supersonic speed, what would the effect be on the bullet? Obviously the 9mm bullet would go backwards in the gun since it's going slower than the plane, and your receiver would explode in your face and probably kill you. Because of this and the Earth's rotation, you need to make sure you fire any guns only when facing west. Only if its a glock, otherwise physics still applies. 
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Posted: 5/18/2015 5:20:23 PM EDT
[#42]
It seems the OP's actual question is how much air drag is too much air drag to allow a given projectile to fire, and at what conditions can this be achieved?
Of course, that wasn't his original question, but that does seems to be where it has morphed to. |
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Posted: 5/18/2015 5:21:20 PM EDT
[#43]
So, if you are flying at 2000 fps and fire a bullet backwards at 2000 fps, will it just fall straight down as soon as it leaves the barrel?
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Posted: 5/18/2015 5:24:23 PM EDT
[#44]
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So, if you are flying at 2000 fps and fire a bullet backwards at 2000 fps, will it just fall straight down as soon as it leaves the barrel? From the perspective of a stationary person on the ground, yes. See Mythbusters soccer ball experiment a few pages back. |
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Posted: 5/18/2015 5:25:01 PM EDT
[#45]
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Did you realize that aircraft taking off in a westward direction actually slow the Earths rotational velocity? 
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Posted: 5/18/2015 5:27:12 PM EDT
[#46]
Quote HistoryQuoted: 80MPH. Or 10 MPH. it is relative. Quote HistoryQuoted: Quoted: Quoted: Quoted: And what happens? You catch up with the ball as it looses forward momentum. What is the velocity of the ball the instant it leaves your hand? 80MPH. Or 10 MPH. it is relative. Exactly, relative to the sidewalk observer, the speed of the ball is 80mph. That's 70 + 10. Same thing with the bullets fired from an airplane gun. Speed of bullet fired + speed of plane. |
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Posted: 5/18/2015 5:27:52 PM EDT
[#47]
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That may be true however most of you who THINK you have it figured out are also forgetting something very important. What altitude is this supersonic aircraft at? At sea level is vastly different than 35,000'. That will have a huge effect on the drag force experienced by the projective. And, no matter what anyone says, the bullets will start to drop away from the aircraft's line of travel as soon as they leave the barrel. They will accelerate towards the earth's center at 9.80655 m/s^2. The plane, assuming level flight, is not. You can't run into your own bullets unless you yourself are in a dive. Quote HistoryQuoted:
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<Layer60's stuff culled from the quote tree>
Quoted: Air is a coefficient? What other coefficients are you talking about here? We are talking about initial velocity here. What effect air has on the projective has nothing to do with the initial velocity. The drag force exerted by the air begins when the bullet exits the barrel, not before. You are wrong. As shown above as well, drag isn't significantly higher above the transsonic region with increased velocity. Therefore, the drag force experience by the projective at say mach 1.5 may be HIGHER than it would be at mach 2.5. The in-flight muzzle velocity is going to be slightly lower than what you'd see in a ground test because of the initial stagnation pressure in the barrel. The difference is small, maybe a tenth of a percent when you work out the math. The drop and maybe drift are also going to be very strong functions of aircraft speed. The drag force is a function of V2, so if you double the speed of the projectile, you have roughly quadrupled the drag force - the small variations in drag coefficient at those velocities is not that significant. And drift is weird, because I think a moving aircraft means you effectively have a variable twist - but I haven't fully thought this out. That may be true however most of you who THINK you have it figured out are also forgetting something very important. What altitude is this supersonic aircraft at? At sea level is vastly different than 35,000'. That will have a huge effect on the drag force experienced by the projective. And, no matter what anyone says, the bullets will start to drop away from the aircraft's line of travel as soon as they leave the barrel. They will accelerate towards the earth's center at 9.80655 m/s^2. The plane, assuming level flight, is not. You can't run into your own bullets unless you yourself are in a dive. Humor me for a moment and pretend I'm an aerospace engineer. Fdrag = 1/2 * rho * V2 * Cd * A Air density (rho) and drag coefficient (Cd) are linear terms, but the velocity term (V) is squared - hence drag being mostly a function of V2 In fact, for the G1 reference projectile, the above equation using a fixed-value Cd does a good job of predicting drag force over practical small arms velocities if you just use Cd = 0.56. For a 5.56x45 77SMK, a fixed value of Cd = 0.345 works pretty good out to 800 yards. Fixed values work ok, but for those wanting variable drag, here's the G1 drag coefficient out to 4200 fps (don't let the polynomials extrapolate beyond the ranges shown unless you want garbage answers). 
Where drag coefficient was highly variable in the transonic region, once you incorporate that variable Cd into the drag force equation, that's where you see the dominance of the V2 term, and that we are largely nit picking when it comes to variable drag coeffiicents. This chart is for deceleration (fps/s). Multiply by the projectile mass to get the drag force at any point on the curve. (F = m*a) 
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Posted: 5/18/2015 5:28:30 PM EDT
[#48]
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So, if you are flying at 2000 fps and fire a bullet backwards at 2000 fps, will it just fall straight down as soon as it leaves the barrel? With the presumption the muzzle were outside the plane. V = sum(v) = 2000 + (-2000) = 0. See mythbusters vid shown earlier in thread. But it would be spinning like a mofo though, so there is that. |
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Posted: 5/18/2015 5:29:29 PM EDT
[#49]
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Humor me for a moment and pretend I'm an aerospace engineer. Quote HistoryQuoted:
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... Humor me for a moment and pretend I'm an aerospace engineer. 
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Posted: 5/18/2015 5:30:44 PM EDT
[#50]
What's the treadmill count so far?
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