Question

A person stands on a bathroom scale in a motionless elevator. when the elevator begins to move, the scale briefly reads only 0.66 of the person's regular weight. calculate the magnitude of the acceleration of the elevator.

Answer 1

M×g+m×a=m×g×0,66. :m
g+a=g×0,66
a=g×0,66-g=g×(0,66-1)
a=9,81×(-0,34)=-3,3354
The acceleration is negative which means he is moving downward.
The force of Weight is F=m×g and you have to add m×a for the acceleration of the elevator.