Question

A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.74 of the person's regular weight.

Calculate the magnitude of acceleration of the elevator.

Find the direction of acceleration and why.

Answer 1

The weight registered on the scale will show zero if the elevator is in free-fall.
If the elevator is accelerating downwards, the scale will register less than the actual weight.

Let m=mass of the person,
a=acceleration downwards,
g=acceleration due to gravity, 9.8 m/s/s
then
net force on the scale
=m(a-g)=0.74mg
a-g = 0.74g
a=(1-0.74)g=0.26g m/s/s