Question

If you are standing on a weighing scale in an elevator what happens to your weight if the elevator accelerates up or accelerates down ?

Are you going to weigh less, weigh more or the same?

Please explain.
Thanks!

Answer 1

The keyword here is accelerate. What causes a force? It's just a mass times an acceleration. So if you have both of those components along with a force vector of gravity, just add them together. Draw a picture if you're having trouble!

Answer 2

Also, keep in mind that the elevator is directly being affected by the acceleration, not you.

Answer 3

If u r going up, I think the weight would be: m(g+a)
When going down, the weight would be: m(g-a)
I think so, but not sure.

Answer 4

I agree, Kainiui. The weighing scale that you stand on, does NOT measure the gravitional force with which the earth pulls you. It measures the normal contact force applied by the surface to you(which is generally equal to the weight, unless the body is accelerating.
If you accelerate downwards, you are moving along with gravity. Now, the normal force needs to be higher in order to balance your weight and the additional force that is pulling you downwards. So, the reading will be higher.
When you accelerate upwards, you are moving against gravity. The opposite happens, the normal force has to be less, because the force that is pulling you upwards, also balances your weight(so the normal force has a partner now). So, the reading will be less.

Answer 5

Mani Bhai, am I correct?

Answer 6

No, Aadarsh, I dont think so. See, wherever you are on earth, your weight will be mg(if you are not considering a very high height or a very low depth from the surface). If you are accelerating, your weight does not change. The normal force changes, but in an elevator you feel like your weight has changed. This is known as perceived gravity.
Your values are correct, but it will be reversed.
For upwards: Reading will be m(g-a)
For downwards: Reading will be m(g+a)
You can see why through a free body diagram.

Answer 7

Oooooooo!!!!! But why does it reverse?

Answer 8

When you're going down, you're going to weigh less. Review the concept of apparent weightlessness :)

Answer 9

Oh, really, I apologise for the mistake. Thanks @morningrsh, and @Aadarsh, you are correct.

Answer 10

you can draw a force diagram