Question

a weightlifter lifts a 1000 newton barbell above his head from the floor to a height of 2.5 meters. he holds the barbell there for 5 seconds. how much work does he do during the 5 second interval?

Answer 1

Work done = Potential Energy  = (mg)h

               mg   =  weight of the ball
 
               = 1000 N * 2.5 m  = 2500 Joules.

The work done during the 5 second is 2500 Joules.