Elevator physics question?

Question

Zach, whose mass is 78 kg, is in an elevator descending at 10 m/s. The elevator takes 2.0 seconds to brake to a stop at the first floor.

What is Zach's apparent weight before the elevator starts braking?

What is Zach's apparent weight while the elevator is braking?

Answer 1

While slowing down, it accelerates upward at (10m/s) / (2s)= 5m/s^2

So before it starts braking, his apparent weight is:

w = mg = (78kg)(9.8m/s^2) = 764.4N

Then when it starts braking, it's:

w = m(g + a) = (78kg)(9.8m/s^2 + 5m/s^2) = 1,154.4N

After it stops, it goes back to 764.4N