Hello, first post. I hope that someone can help me with this. I will roughly summarize the problem, and what I've done thus far.(adsbygoogle = window.adsbygoogle || []).push({});

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

A lady was in an elevator that free-fell 6 feet and abruptly came to a halt. We had to determine a reasonable best case and a reasonable worst case value for the impact force that she experienced. The weight of the elevator is unknown and we are to find a value which I have not done yet. The woman weighs 140lbs.

2. Relevant equations

x = x_0 + v_0*t + (1/2)a*t^2

F= ma

3. The attempt at a solution

For the worst case I made the assumptions that all the weight was acting on one ankle and that the elevator hit the ground and came to a direct stop instantaneously.

The forces I had acting were her body weight, the weight of the elevator, and the ground reaction force.

I ended up with this:

F = 0 = -623.63 (N, bodyweight acting in the neg. direction) -Welevator(Weight of the elevator) + GRF (Ground reaction force)

Thus:

GRF = Welevator +623.23N

This was rather simple and once I find a weight of the elevator I should be fine.

My issue comes in the Best case scenario, where I assumed that the body weight was equally distributed through both ankles and that the elevator decelerates.

I had 1/2BodyWeight going through each ankle, the Welevator going through the middle, 1/2 of the GRF acting on each ankle.

I used:

x = xo + vo*t +1/2a*t^2

0 = 1.8288m + 0t + 1/2(-9.8m/s^2)*t^2

t = .61sec

Not sure if I can use this here, and my problem is deciding how I would get the force from there. I'm assuming I would need a vf and a vi as well as the mass of the elevator which I mentioned before. Would Impulse=momentum work here?

Any and all help would be greatly appreciated. Thanks in advance.

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# Homework Help: Woman in Elevator Problem (Free Fall), Forces she experiences?

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