Both a 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power expended in raising the 50-kg sack is

Question

Quizplus · Accepted Answer

The power expended is given by the formula P = W/t, where W is the work done and t is the time taken. 
Now, work done in lifting the 50-kg sack = mgh = 50 x 9.8 x 2 = 980 J. 
Work done in lifting the 25-kg sack = mgh = 25 x 9.8 x 4 = 980 J. 
Since both sacks require the same amount of work, the power expended in both cases will be the same (assuming the same time taken). Therefore, the answer is C.

Both a 50-Kg Sack Is Lifted 2 Meters from the Ground