A man of 50 kg is standing on a weighing machine in a lift. As the lift moves with a constant acceleration, the weighing machine registers the man's weight as 45 kg. State whether the lift is ascending or descending. Give reasons for your answer. What is the acceleration of the lift? [ g = 9.8 `m cdot s^(-2)` ]

Explanation

The weighing machine shows a reading lower than the real weight of the man. So, the lift is descending with as acceleration, because in such cases, apparent weight R = m(g - a) `lt` mg.
The downward acceleration
a = g - `( R)/(m) = 9.8 - (45 xx 9.8)/(50) = 0.98 "m"cdot s^(-2)`.