Answer:
M au = Fs - M g au = upwards acceleration; Fs = scale reading
Fs = M (au + g) scalar quantities where g is positive downwards and au is positive upwards - Fs is the net force acting on the person
If the acceleration is zero Fs = M g and the scale reads the persons weight
If the elevator is decelerating then au is negative and the scale reading Fs = (g - au) M and the scale reading is less than the weight of the person
