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 theorem
Wgravity + 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 = -600J
now w.d. = F x s
F= -600/50 = -12N