Gravitational Force elevator questions

[sweet877]

A student stands on a bathroom scale in an elevator at rest on the 64th floor of a building. The scale reads 836 N.
a) As the elevator moves up, the scale reading increases to 935 N, then decreases back to 836 N. Find the acceleration of the elevator.
b) As the elevator approaches the 74th floor, the scale reading drops as low as 782 N. What is the acceleration of the elevator?

Fnet = ma
F-mg = ma

This is all I've got so far...I'm thinking I need to find the force exerted by the elevator on the student. How?

Thanks.

 

[andrewchang]

https://www.physicsforums.com/showthread.php?t=97884&highlight=elevator

exact same problem.

 

[sweet877]

Oh wow...thanks!

 

[lightgrav]

The scale readings are the Force exerted by the elevator on the student.
Did you draw a sketch of this?
The only thing touching the student is the scale!

 

[sweet877]

I drew a diagram, but somehow mistakenly thought that it is the scale exerting the force, and the elevator played no part in it. I get it now! Thanks very much for your help, lightgrav!