A body of mass 2 kg is at rest at a height of 10 m above the ground. a) Calculate its potential energy and kinetic energy after it has fallen through half the height. b) Find the velocity at this instant.
Total energy at B = kinetic energy + potential energy = 0 + mgh = 2 x 9.8 x 10 = 198 J It descends half the height, it loses potential; energy which is given by h = mg 2 = ½ mgh = 98 J Its potential energy at C = (196 – 98) = 98 J The loss of potential energy = gain in kinetic energy = 196 – 98 = 98 J Kinetic energy = ½ mv2 ½ x 2 x v2 = 98 v 2 = 98 = 7√2 m/s
7√2 m/s
