Question

A ball of mass 2kg is dropped from a height get height . What is the work done after 2sec after the ball is dropped?

Answer 1

Distance it falls:
h = ½gt² = ½(9.8)(2)² = 19.6 meters
speed after 2 sec
v = gt = 19.6 m/s

PE lost = mgh = 2•9.8•19.6 = 384 J
KE gained = ½mV² = ½(2)(19.6)² = 384 J
now workdone =change in kinetic energy
at t=0 k.e=0
at t=2 k.e=384 joules
answer is 384 joules