# Free fall or what?

1. Aug 16, 2006

### cterence_chow

free fall or what??!?

I would like to know,
if we are on a lift going upwards, and we happen to be standing on a weighing machine, why does our the value appears more than when we just weigh in the stationary lift??

2. Aug 16, 2006

### Danger

That's just the inertia of your body causing it to stay put for as long as possible. Both it, and the top of the scale itself, thus apply pressure to the bottom of the scale. Note that this occurs only during the acceleration phase of the elevator travel. By the same token, when it decelerates for the next stop, your apparent weight will drop.

3. Aug 16, 2006

### cterence_chow

Then what if the lift is just accelerating downwards??Won't our apparent weight will also be less?

4. Aug 16, 2006

### Danger

For sure. As long as there's a positive acceleration, your weight will increase. With negative acceleration, it will decrease. Once a constant speed is reached in either direction, your weight will be normal (excluding relativistic effects which don't apply at that speed or within your own reference frame).

5. Aug 16, 2006

### neurocomp2003

E=mgh Potential Energy

6. Aug 16, 2006

### Staff: Mentor

Clarification: the change in weight only occurs during the acceleration. The wording in the OP implies it occurs all the time when going up.

7. Aug 17, 2006

### samsool

F = ma.. in equilibrium,our body's weight is forcing downward. and there is a reaction force(same value and upward)= newton's third law.when the lift is moving upward, the force acting upward increases. and that force also has a reaction force acting downward. this reaction force will be add to our weight value...

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook