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Posted: 8/3/2005 10:04:24 PM EDT
[#1]
took me a while to get that  How about Mass never changes, but you weigh less on the moon! 
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Posted: 8/3/2005 10:05:50 PM EDT
[#2]
F=Ma. That is The Theorem, from The Man. Sir Isaac Newton. Understand that, and you understand it all.
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Posted: 8/3/2005 10:08:06 PM EDT
[#3]
... Mass varies due to inertia (relative acceleration)
... Density (or weight) is stable and gaged roughly to any given material's specific gravity (1 equal to that of water). |
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Posted: 8/3/2005 10:10:31 PM EDT
[#4]
Real simple? Mass is the amount of stuff. Weight is gravity's effect on you. Weight varies for example if you were standing here on Earth, then on the Moon. Your weight would be different. Your mass would remain the same.
Weight is a fancy word for "force of gravity". F=ma or W=mg |
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Posted: 8/3/2005 10:10:52 PM EDT
[#5]
Weight = mass x acceleration of gravity or F=ma as the guy above says.
It is a measure of the force due to your mass being pulled down by gravity. It varies, at least someowhat, virtually everywhere in the universe. mass is constant at a given time. Basically it means you are composed of so many atoms... Weight is the force on them. WEightlessness: Not because there is no gravity in space (it is about 99% for object in low orbit) but becuase the bottom is dropping out from under you to keep up with the curvature of the Earth. That is in orbit of course but in any event, you would have no weight but still the same mass. |
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Posted: 8/3/2005 10:11:34 PM EDT
[#6]
She and I both fully understand the concepts behind this lesson, I am looking more for a unique lab experiment. Thanks.
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Posted: 8/3/2005 10:12:58 PM EDT
[#7]
Slugs.
Slug (mass) From Wikipedia, the free encyclopedia. For other meanings, see Slug (disambiguation) The slug is an English and U.S. customary unit of mass. The slug is part of a subset of coherent units known as the gravitational foot-pound-second system, one of several such specialized systems of mechanical units. It is the mass that accelerates by when a force of one pound-force (lbf) is exerted on it. Therefore a slug is about 32.174 05 pounds or 14.593 90 kg. The term metric slug appears as a footnote in the 1967 seventh edition of Marks Standard Handbook for Mechanical Engineers. Also called a hyl, or the TME from a German acronym, it is the mass that accelerates at 1 m/s² under a force of 1 kgf. Because 1 kgf = 9.806 65 N, the metric slug is 9.806 65 kg. A more complete discussion of imperial and U.S. customary units of force and mass is given at pound. en.wikipedia.org/wiki/Slug_(mass) |
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Posted: 8/3/2005 10:14:05 PM EDT
[#8]
Considering the target audience (read as "11 and 12 year olds") and the need for some seriously intricate equipment to Visually demonstrate the difference, she's basically looking at a "paper" or theoretical procedure.
Weight = mass x acceleration (mass x gravity) Mass = the sum of sub-atomic particles in an object and is considered constant. You feel "weightless" at the apex of a rollercoaster because you hit a point of zero acceleration... but your mass does not change (unless you toss your cookies!) The biggest obstacle to students latching on to the difference is our crazy use of the same units to measure mass AND weight (kilograms, pounds, etc..) Students can go nuts trying to wrap their minds around the concept that something on earth can have a MASS of 1 kg, and weigh from .95kg to 1.02 kg (depending on altitude) to weighing almost nothing in orbit. ETA - Rebel, the correct term would be "Microgravity"... As an astronaut's orbit is not stable or permanent, there is a measurable acceleration. We're talking in the hundred to thousandths of m/s^2, but still there. |
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Posted: 8/3/2005 10:18:45 PM EDT
[#9]
... Easy ... Have her lab weigh a static one-ounce billet. Record its weight. ... take same billet and position it in a sling using a load cell and whirl it around her head and record its weight again. ... Test, document and record then test, document and record test, document and record. |
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Posted: 8/3/2005 10:20:16 PM EDT
[#10]
How would you determine an objects mass on the moon?
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Posted: 8/3/2005 10:24:12 PM EDT
[#11]
With a scale.. and factor in the acceleration of gravity encountered on the moon.... Approx 1/6 that of Earth. IE: using a scale that was calibrated on Earth.. "Weigh" said object... Its mass will equal the reading on the scale multiplied by 6. (Approx.) Or (as the smart-ass student is bound to say.....) bring it home and weigh it here!!! |
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Posted: 8/3/2005 10:26:50 PM EDT
[#12]
... Multiply your static earthly density (weight) by .166 unless inertia is applied ... Come on man! This ain't rocket science! 
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Posted: 8/3/2005 10:27:18 PM EDT
[#13]
Almost backwards. Mass is matter. weight is mass in acceleration, as in gravity of Earth. Scales measuer weight because it is force deflecting a spring. Balances compare mass. A scale will indicate different weight for a given mass depending on the gravitation/acceleration but a balance will ALWAYS indicate a constant mass, regardless if you measure a 1 kg mass on the Earth, Moon or Saturn. Density takes into account volume. |
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Posted: 8/3/2005 10:33:33 PM EDT
[#14]
I would explain atomic electron spin rates(atomic weights of the periodic table) and how gravity is the relationship(attraction) between two (mass)objects. More spin/amount of electrons = more gravic attraction.
Or just have them read or listen to the audiobook Stephen Hawking - The universe in a nutshell. |
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Posted: 8/4/2005 2:20:47 AM EDT
[#15]
I used a swingset to explain it to my daughter when she was in school. Try to stop my youngest at the bottom of the swing cycle, compare that to pushing her from a standstill, and then compare that to stopping her during a swing cycle when it's almost at the back end.
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Posted: 8/4/2005 2:24:08 AM EDT
[#16]
Sounds like field trip time to an amusement park for some G-inducing rides.
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Posted: 8/4/2005 3:26:31 AM EDT
[#17]
Not even close. Mass never varies. |
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Posted: 8/4/2005 3:34:28 AM EDT
[#18]
Not exactly correct. Mass cannot be destroyed, but it can be converted to Energy and vice versa. But in everday life, Mass won't vary (much). |
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Posted: 8/4/2005 6:09:51 AM EDT
[#19]
Does her school have an elevator, cause we're gonna need an elevator.
Get a scale, one that works by stretching or compressing a spring, hang the object to be weighed from the scale, let it come to a rest, observe the weight change as the elevator goes up from a rest and as it comes down from a rest. Of course we are actually observing the effect of acceleration on a mass (the mass doesn't change) and how the weight changes. Like I said first build a school tall enough to need an elevator. 
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Posted: 8/4/2005 6:18:11 AM EDT
[#20]
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Posted: 8/4/2005 6:23:40 AM EDT
[#21]
I can e-mail around and find you a lab if you still need one.
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Posted: 8/4/2005 6:26:58 AM EDT
[#22]
Same way we do here on Earth -- with a balance. Start stacking stuff of known mass on one side until it balances the stuff of unknown mass on the other side. |
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Posted: 8/4/2005 6:31:30 AM EDT
[#23]
Off topic! 
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Posted: 8/4/2005 6:38:40 AM EDT
[#24]
Here is one www.raft.net/ideas/Measuring%20Mass.pdf, but I would use a triple beam balance.
This is what I would use to keep it simple. www.edinformatics.com/math_science/mass_weight.htm |
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Posted: 8/4/2005 6:55:52 AM EDT
[#25]
all electrons in the universe have the exact same spin and they never change. electrons contribute almost nothing to the mass of an object. electron spin has nothing to do with gravity. the best way to demonstrate the difference between mass and weight is to use a combination of two of the posters above. Put a scale and a balance on an elevator with identical weights on them and see how the scale changes when the elevator accelerates but the balance does not. |
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Posted: 8/4/2005 7:00:58 AM EDT
[#26]
In the museums they usually have a simple scale show the difference. One is set to show your weight on earth the other is set to show your weight on the moon, mars, or jupiter. Thus proving that even though your "weight" changes your mass is the same.
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Posted: 8/4/2005 7:06:55 AM EDT
[#27]
The elevator experiment sounds pretty good.
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Posted: 8/4/2005 7:21:57 AM EDT
[#28]
"Mass" is a contraction of "massive" as in "yo, her calves were mass!"
"Weight" is how long before something happens, as in "yo, slick, weight here and I will bring you a ho with some serious mass!" * This post was approved by the NEA and the Oakland Board of Public Schools * |
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Posted: 8/4/2005 7:31:47 AM EDT
[#29]
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Posted: 8/4/2005 8:17:26 AM EDT
[#30]
Here's a thought on an experiment that might be feasible.
Use an aquarium in conjunction with spring scales and balances. Take some steel pipes and cap them off. This will make them at least somewhat buoyant (but make sure they're still negatively buoyant). Bouyancy is just an upward force being exerted by the water, so it has the effect of counteracting gravity (downward force). Take the pipes, weigh them on the spring scales and on the balance outside of the tank, then do so inside the tank (if she could find a cheap balance that she could submerge). End result will be that the balance always shows the same whether in water or out (same mass). Spring scales on the other hand will show lower "weights" in the water versus out. |
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Posted: 8/4/2005 8:22:02 AM EDT
[#31]
+1 |
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Posted: 8/4/2005 8:28:12 AM EDT
[#32]
As for the demonstration, here's an idea:
She explains to the kids that weight is actually force, as explained already in this topic. To show this, she attaches a scale to the ceiling, and pushes up on it, and has the kids look at the reading. Then she gives the relevant equations. It would be a lot easier if we could manipulate gravity. Then all you'd have to do is have a scale and a triple beam balance, then mass the object and weigh it in normal gravity, and then in, say, 1/2 gravity. Since the balance would show the same reading, and the scale would show a different reading, that would be a good demonstration. |
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Posted: 8/4/2005 8:35:38 AM EDT
[#33]
Take two objects that are different weights and sizes and drop them together, showing how gravity affects them the same. Next take two objects that weigh the same, but have different masses, and drop them in the water tank, the denser mass should hit bottom first. The resistance generated by the water should magnify the effect. |
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Posted: 8/4/2005 12:38:07 PM EDT
[#34]
Actually no. It souldn't make any difference in water or air for mass, only the size and shape of the object has an affect. It would be more pronounced in the water. Density would make a difference, but that is something else.
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Posted: 8/4/2005 1:03:22 PM EDT
[#35]
You can translate weight into a horizontal direction.
Placed on a frictionless (or very low friction) surface an object may slide around at will. It still requires a fixed amount of force to accelerate the objects at 1 G. Be creative on how to demonstrate this. Ball Bearings or marbles on a metal/glass plate can provide a nearly frictionless surface for flat items. Can you get those little tiny spherical sand grains that are used for table top bowling type games? Ask students why a weightless falling baseball, exerts force on your hand when you catch it. |
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Posted: 8/4/2005 1:03:22 PM EDT
[#36]
tag
But before I come back - These are kids with no understanding of higher math (or even meduim math), electrons (let alone spins and all the other complications), or most of the rest suggested above. The trick is to come up with a physical demonstration to drive home the properties. Mass is a measure of how much stuff you have in a particular volume - that volume of stuff has a property called mass that is constant everywhere in the universe if the volume and the stuff remain unchanged. [If it gets converted to energy, then it's not mass any more, as one helpful poster offered above.] Different stuff in identical volumes will produce objects of different mass, and that mass will never change if the stuff and the volume don't change. Weight is a type of force. It's always a force. It's never a mass. The most familiar form of weight for earth dwellers is a mass that is in the earth's gravity field - weight = mass X [the acceleration of gravity, g] Other forces can be generated by introducing other types of accelerations to a mass; centripetal force produced by swinging a bucket full of water, is one. A lab demonstration of mass and weight is also going to require a discussion of density and volume. Here's a start - take two objects of obvious identical dimension and different density. Dunk them in a beaker to demonstrate that they displace identical volumes of water. Then weigh them to show that one weighs more. I need to think about a way to tie this all together to make sense without resorting to math; it may not be entirely possible. The internet has all sorts of science curriculum resources for teachers. The first place to look is a the NASA site. |
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Posted: 8/4/2005 1:07:09 PM EDT
[#37]
with a balance that had a set of known mass "weights" to balance the object you are measuring |
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Posted: 8/4/2005 1:10:38 PM EDT
[#38]
You are discussing density. That isn't necessary when drawing a distinction between weight and mass. Tape a bowling ball to a scale and drop it onto a pillow. Record the weight while it is falling. Record the weight of the bowling ball stationary on the scale. Discuss the differences in the reading. Does the object weigh less while it is in freefall? Why do objects weigh less in freefall while they have not changed in any other way? How does weight differ from inertia? Can you get injured by a 30 MPH car while it is floating in space, (assuming you are stationary)? Why? An asteroid may be as massive as an entire state, but it is floating in space at 1 mile per hour. Can you reach out your hand and stop it? Why not? ** These are all questions that you can ask the students. Explain that weight is the effect that gravitational acceleration has on mass. Substitute other types of acceleration and you get a good illustration. |
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Posted: 8/4/2005 1:27:18 PM EDT
[#39]
You would push it a known horizontal distance with a known force across a frictionless surface. That way you can get it from F = ma where the "a" has no gravitational component. P.S. springs are good ways of getting "known" forces. ETA: Yeah, what Torf said. 
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Posted: 8/4/2005 1:28:21 PM EDT
[#40]
This isn't really "weight" (force due to gravitational) acceleration), but it is good enough for middle school
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Posted: 8/4/2005 1:30:34 PM EDT
[#41]
I would say that absent gravitational control, and a good explanation of how gravity works, It would give kids a really good illustration. |
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Posted: 8/4/2005 2:45:58 PM EDT
[#42]
Yeah, I think that's what I said.
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Posted: 8/4/2005 2:48:37 PM EDT
[#43]
+1 You can derive the rest!
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Posted: 8/4/2005 5:34:30 PM EDT
[#44]
Somehow you also have to define acceleration in an format understandable to 6th graders. I never thought about this before, but these concepts are difficult to explain at this level. I'm looking at some on-line sites, but haven't found anything. I don't think you can teach mass and weight in isolation from matter, volume, density, acceleration, and probably momentum at the minimum; you have to define and build on each concept in turn. Also, in before the +0.999bar's  |
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Posted: 8/4/2005 8:38:37 PM EDT
[#45]
Even general relativity....? 
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Posted: 8/4/2005 9:15:44 PM EDT
[#46]
According to the ASSHOLE physics profs at USNA, you could derive the recipe for Chicken Kiev from that thing, let alone relativity. 
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Posted: 8/5/2005 6:59:09 AM EDT
[#47]
electron spins are different...whether its a spin 1/2 or -1/2 or spin 1....etc. However you are almost right by saying that "electron spin has nothing to do with gravity.", but it does. You cannot just leave gravity out of your equation just to make your equation work, even if the force is almost zero. This is the main problem with 1960's "relativity", it negates gravity because its force is so small at the quantum level (or so we believe), its just that we dont understand it completely. I guess this is something a bit to advanced for his six grade class, ehh   |
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Posted: 8/5/2005 3:35:39 PM EDT
[#48]
Well, I have seen people who do not understand physics say such things, but feel free to go back and challenge them to derive (even special) relativity and quantum mechanics from Newton's laws of motion. Watch them squirm. 
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Posted: 8/5/2005 6:02:43 PM EDT
[#49]
Thats a hard one to devise an experiment for. I was tempted to cheat and suggest the weighing in air and again in water, but that isn't really an illustration of mass vs weight.
The real experiement to demonstrate it would involve taking a mass and putting it into as close to a frictionless environment as possible, applying a fixed force and measuring the acceleration. Then weigh the mass. Now repeat the same thing with a different gravity. The MxF would be constant, but the weight would not. The hard part is varying gravity... This is about the only true experiment I can think of to really demonstrate the principle. |
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