A man of mass 70 kgstands on a weighing scale in a lift which is moving (a) upwards with a uniform speed of 10 m s^(-1) , (b) downwards with a uniform acceleration of 5 m s^(-2), (c) upwards with a uniform acceleration of 5 m s^(-2) . What would be the readings on the scale in each case? (d) What would be the reading if the lift mechanism failed and it hurtled down freely under gravity ?

A man of mass 70 kgstands on a weighing scale in a lift which is movin

1.	A man of mass 70 kgstands on a weighing scale in a lift which is moving (a) upwards with a uniform speed of 10 m s^(-1) , (b) downwards with a uniform acceleration of 5 m s^(-2), (c) upwards with a uniform acceleration of 5 m s^(-2) . What would be the readings on the scale in each case? (d) What would be the reading if the lift mechanism failed and it hurtled down freely under gravity ?
Answer» SOLUTION :The reading on the scale is a measure of the force on the floor by the man.By the THIRD Law, this is equal and opposite to the normal force N on the man by the floor. (a) `N = 70 xx 10 = 700 N : ` Reading is 70 kg (b) `70 xx 10 - N = 70 xx 5` : Reading is 35 kg (c ) `N -70 xx 10 =70 xx 5` : Reading is 105 kg (d) `70 xx 10 -N = 70 xx 10`: Reading would be ZERO, the scale would be read zero .