An elevator is moving down at a constant rate of 4 m/s. A person is standing on a scale that says the person weighs 80 N. When it reaches the bottom, it comes to a stop in 2 seconds.
During the stopping process, what is the reading on the scale?

The reading on the scale is 96.31 N.

Explanation:

When the elevator comes to a stop the speed decreases from 4 m/s to 0 m/s.

This means that it incurs deceleration. We can use the formula below to find out the force that is applied on the person during this deceleration:

F = mass * acceleration

Assuming the deceleration is constant, we have the following equation:

V = U + at

Where V = Final speed = 0

U = initial speed = 4

a = acceleration

t = time

Solving, we get:

0 = 4 + 2a

a = -2 m/s^2

Thus the object decelerates at 2 m/s^2

The mass of the person = 80 / 9.81 =  8.155 kg

F = 8.155 * 2

F = 16.31 N

Total weight = 80 + 16.31 = 96.31 N  (This is the reading on the scale)

answer would be letter choice (a),   a ball resting on a shelf. would be another example of potential energy   >   stored energy > not moving.

a ball spinning on a finger   >   kinetic energy > moving energy

a ball rolling on the ground   >   kinetic energy   > moving energy

a   ball flying through the air   > kinetic energy   >   moving energy

hope that                                         : )