A BALL OF MASS 2KG IS DROPPED FROM A HEIGHT. WHAT IS THE DONE BY ITS WEIGHT IN 2 SECONDS AFTER THE BALL IS DROPPED?

HERE, mass,m=2 kg

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  {Ans.}