A 75.0 kg person stands on a scale in an elevator. (a) What does the scale read (in N and in kg)when the elevator is at rest?
The person's weight is (mass) x (gravity) = (75 kg) x (9.8 m/s²) = 735 newtons. When the elevator is at rest, or moving up or down at a constant speed, the scale reads 735 newtons. When the elevator starts moving upward from rest, or moving down but getting slower, the scale reads a higher number of newtons. When the elevator starts moving downward from rest, or moving up but getting slower, the scale reads a smaller number of newtons. A properly marked scale will never read anything in kilograms, because 'kilogram' is a unit of mass, not force or weight.