Why would his weight be zero at the moment of the fall?

alaa amed · May 2, 2016

1. The problem statement, all variables and given/known data

A person of weight w is in an upward-moving elevator when the cable suddenly breaks. What is the person's apparent weight immediately after the elevator starts to fall?

Chestermiller · May 2, 2016

alaa amed said: ↑

1. The problem statement, all variables and given/known data

A person of weight w is in an upward-moving elevator when the cable suddenly breaks. What is the person's apparent weight immediately after the elevator starts to fall?

How would you personally define the term "apparent weight?"

alaa amed · May 2, 2016

Chestermiller said: ↑

How would you personally define the term "apparent weight?"

I think that's the key to answering the question, though I am not sure I interpreted properly. I think it means the weight relative to the force of gravity that acts on it in particular instance.

Chestermiller · May 2, 2016

alaa amed said: ↑

I think that's the key to answering the question, though I am not sure I interpreted properly. I think it means the weight relative to the force of gravity that acts on it in particular instance.

That's not correct. It means that, if he was standing on a scale, what the scale would read (i.e., the normal force the person would be exerting on the scale, and, by Newton's 3rd law, the normal force the scale would be exerting on the person). That's the definition of his apparent weight.

So, what is the normal force that the scale is exerting on the person if the elevator cable has been cut?

alaa amed · May 2, 2016

Chestermiller said: ↑

That's not correct. It means that, if he was standing on a scale, what the scale would read (i.e., the normal force the person would be exerting on the scale, and, by Newton's 3rd law, the normal force the scale would be exerting on the person). That's the definition of his apparent weight.

So, what is the normal force that the scale is exerting on the person if the elevator cable has been cut?

I think the person and the elevator would be free falling an so there would be no contact force?

Chestermiller · May 2, 2016

alaa amed said: ↑

I think the person and the elevator would be free falling an so there would be no contact force?

Yes. That is correct. So what does that mean regarding the "apparent weight" of the person, considering the apparent weight is equal to the contact force.

alaa amed · May 2, 2016

Chestermiller said: ↑

Yes. That is correct. So what does that mean regarding the "apparent weight" of the person, considering the apparent weight is equal to the contact force.

It will be zero! Thank you so much for your help.
I get it now.

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Why would his weight be zero at the moment of the fall?

alaa amed

Chestermiller

Staff: Mentor

alaa amed

Chestermiller

Staff: Mentor

alaa amed

Chestermiller

Staff: Mentor

alaa amed

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