Whats the difference between weight and the energy to move something?

Question

I had a pallet of steel that weighed 3,000 lbs. That was the gravity pulling down on it. I could wheel it around my building with some effort but I know it was not 3,000 lbs. worth. What is this called? I mean the weight of an object being accelerated in space. Can you explain some more about it, like the ratio of that compared to the gravitational weight or some other neat facts.

Answer 1

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Answer 2

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I know this is kind of abuse, but you don't take email, I had no other way of reaching you.

With your above question you would have loved my 6th grade science teacher. Where do you guys come up with this stuff?

Now in answer to your question, the ratio compared to the gravitational weight is 97.8% .    However, are you moving this on a flat plain? Or, are you at any time moving this down a slanted hallway? That does make a difference.

Answer 3

Suppose the ground is level and you are moving the pallet of steel on a pallet trolley.

Once you have overcome the static friction in the wheels and accelerated it to some steady speed (and ignoring going round corners), the only work you are doing is that required to overcome the rolling friction of the wheels.

You are pulling or pushing with a constant force. That force times the distance you move the pallet and trolley rig is the energy you are expending.

The weight has little to do with it except that it contributes to the friction. More weight, more friction - probably a linear relationship plus a small constant for the trolley on its own with no weight.  

Answer 4

http://en.wikipedia.org/wiki/Pound_(mass...

then

http://en.wikipedia.org/wiki/Rolling_fri...

Answer 5

th gravity is 92.8 percent so it is about 3000 lbs

Answer 6

The force you had to overcome wasn't gravity, as I assume that you weren't actually lifting it up. You had to overcome the friction in the wheels. The mass of the pallet is around 1500 kg. Let's say you were able to apply half your body weight as force. Your weight is (say) 150 lbs, which equates to around 750 N. So you can apply a force of (say) 375 N. Acceleration = force / mass - disregarding friction, you would be able to accelerate the 1500 kg mass by 375/1500 i.e. around 0.25 m/s/s.

HOWEVER, the force that you are trying to overcome in achieving this acceleration isn't the weight of the pallet, it's the friction between the pallet and the ground. If it's on wheels or bearings, the friction might be quite low - even a baby might be able to get a very heavy weight moving (a small child can pull over a bookcase which is much heavier than it, not because it can lift the bookcase, but because only a small force is needed to move the bookcase out of equilibrium). Of course, were the pallet lying on the floor, friction would be much harder to overcome.

If you needed to lift the pallet up, then the significant force you would have to overcome would be the weight of the pallet. But just shifting it, it's the friction.