What Does the Scale Show When the Elevator Accelerates Upwards?

[gxinxing]

Homework Statement

A 60.0 kg woman on a scale is in an elevator. The combined mass of the elevator and the woman is 815 kg. The elevator accelerated upwards, and during the acceleration, the hoisting cable applies a force of 9410 N. What does the scale read during the acceleration?

Homework Equations

F = ma.
Fn = mg + ma

Maybe there's more equations but I'm not sure.

The Attempt at a Solution

Well I first used F = ma to solve for a with F = 9410 and m = 815 kg. a comes out to be 11.5 m/s^2. Then I plugged a into the second equation to get Fn and I got 1280 N, but the answer is 645 N.

 

[Filip Larsen]

Your acceleration is not correct. It may help to make a diagram of the forces acting on the elevator.

 

[gxinxing]

I don't understand the other forces acting on the elevator.

 

[Filip Larsen]

There is one other force acting on the elevator besides the cable force (hint: it points in the opposite direction and relates to the mass of the elevator).