A bag of cement of mass is lifted straight up from ground level to a balcony high
PHYSICS · Multi-part · CBSE · Physics · Work and Energy · Work and Energy
Problem
A bag of cement of mass 8kg is lifted straight up from ground level to a balcony 9m high. The motion is completed in three equal vertical stages of 3m each, taking 5s per stage.
(i) Calculate the potential energy gained by the bag after each 3m lift and the total mechanical work done on the bag when it reaches the balcony. Take g=10ms−2 for quick estimation.
(ii) Determine the average power delivered during the entire 9m ascent.
(iii) If the bag were allowed to come back down to the ground under gravity alone, what would be the sign of the work done by the gravitational force during the descent? Explain briefly.