What does the scale read?

Question

A person stands on a scale inside an elevator at rest (see the figure below). The scale reads W = 752 N.

What is the person's mass?

The elevator accelerates upward momentarily at the rate of a = 3 m/s². What does the scale read then?

The elevator then moves with a steady speed of 6 m/s. What does the scale read now?

Answer 1

First you have to calculate the mass based upon normal gravity because the elevator is not yet moving. So since force is equal to mass times acceleration, in this case, mass is equal to 752÷9.8 m/s squared = 76.2 kg.

Now that the elevators moving upward at an acceleration of 3 m/s squared, this gets added to the acceleration of gravity resulting in the final acceleration of 12.8 m/s squared. So to calculate the weight in newtons during this acceleration time, force is equal to mass times acceleration gives you 76.7 times 12.8 = 982.2 N.

Now when the elevators moving at a constant velocity, there is no acceleration except for the acceleration of gravity so the scale is back to reading the original weight of 752 N