A body of mass 2 kg thrown vertically upwards with a velocity 40 m/s comes to instantaneous rest at a height 50 m. Is there any other force (other than gravitational force), if yes then calculate the value. Ans) Yes , a force due to air drag will be there , to calculate this wehave to first find work done by air drag..Acc. To work-energy theoremWgravity + Wair drag = change in K.E.-Mgh +Wair drag = change in K.E.Wair drag =change in K.E. +mgh=[0-1/2mu2] +mgh = -1/2 x 2 x (40)2 + 2x 10 x 50 = -1600+1000 = -600Jnow w.d. = F x sF= -600/50 = -12N