Homework Help: Elevator Acceleration?

1. Oct 8, 2008

physics111

I'm having a hard time with this question, i've done my share of research/computation and came up with an answer. Though I dont think the answer is correct and it might not even be what the question is asking for. Please help me out, thanks in advance!

Weight in an Accelerating Elevator

Take a bathroom scale and go into an elevator. Read your weight on the scale when the elevator is at rest. If the elevator is moving upwards or downwards you will observe that the reading on the scale changes. Record the maximum and the minimum values read on the scale. Using this information, find the elevators acceleration as it starts moving and as it stops. Make sure your result is given in the SI units for acceleration.
Include a diagram for each case, and show all your calculations.

MY attempt at a solution:
150lbs at rest=68.04kg=666.79N
160lbs at max=72.57kg=711.19N
135lbs at min=61.23kg=600.05N

Fnet=F-mg=ma

711.9N-666.79N=68.04a
45.11-68.04a
a=.65 m/s^2

600.05N-666.79N=68.04a
-66.74N=68.04a
a= -.98m/s^2

2. Oct 8, 2008

nasu

Did you measure these values yourself?
The calculation look OK. What bothers you?

3. Oct 9, 2008

physics111

Yes i measured these values myself quite a few times to be accurate, i dont know i just came up with this answer randomly i'm not exactly sure im on the right track!

4. Oct 9, 2008

merryjman

The acceleration values sound reasonable for an accelerating elevator. And your calculations are correctly set up.

5. Oct 9, 2008

nasu

The calculation is OK as you did it.
Do you have a problem with the values for acceleration? What would you expect?