# Elevator Problem w/ app. Weight

1. Sep 23, 2008

### Bachi234

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

Henry gets into an elevator on the 50th floor of a building and it begins moving at t = 0 s. The figure shows his apparent weight over the next 12 s where w1 = 520, w2 = 720, and w3 = 920.
The graph:
Begins at t=0 at w1 and goes in a horizontal straight line until 2. At t =2 the line goes straight up to w2 and stays horizontal on w2 until t=10. At t=10 the line goes straight up to w3 and stays horizontal on w3 until t=12. At t=12 it goes back down to w2. That is the end of the graph.

1. Is the elevator's initial direction up or down and how?
2. What is Henry's mass? _____kg
3. How far did Henry travel at t=12 sec?_____m

2. Relevant equations

F = ma
Wapp = m(g + ay)
Fsp = w + may
X = Vot + .5a(t)^2

3. The attempt at a solution

Number 1- I got that it is going down but I don't understand why. I think it has something to do with the acceleration being positive. What is a clear explanation for why its inital direction is down?

Number 2- I've been trying to use the apparent weight formula to figure out the mass but I can't do that without the acceleration. After working the equations out using the Wapp and the g, I got that " m = (520 / (9.8 + ay)) " But, I can't fully solve for m without the acceleration and I can't solve for acceleration without the total force or m. I seem to be in a hole.

Number 3- Well, after I get the acceleration I can use time and Vo (which would equal 0, right?) to get the distance traveled.