Zach, whose mass is 73 kg, is in an elevator descending at 12 m/s. The elevator takes 4.0 s to brake to a stop at the first floor. What is Zach's apparent weight before the elevator starts...

Zach, whose mass is 73 kg, is in an elevator descending at 12 m/s. The elevator takes 4.0 s to brake to a stop at the first floor. What is Zach's apparent weight before the elevator starts braking and what is Zach's apparent weight while the elevator is braking?

Expert Answers
justaguide eNotes educator| Certified Educator

Zach has a mass of 73 kg and is in an elevator. Initially the elevator is descending at a constant speed of 12 m/s. Zach's apparent weight during this period is equal to the acceleration due to gravity. It is equal to 73*9.8 = 715.4 N

When the elevator starts to brake it comes to a halt in 4 s. The acceleration of the elevator is 12/4 = 3 m/s^2 acting upwards. The net force exerted by Zach on the floor of the elevator is his weight during this period. This gives Zach's weight during this period of 4 seconds as 73*(9.8 + 3) = 934.4 N