A body of mass 1 kg falls from rest through a distance of 200 m and acquires a speed of 50 m/s. Work done against friction of air is (Take g = 10 m//s^2)

A body of mass 1 kg falls from rest through a distance of 200 m and ac

1.	A body of mass 1 kg falls from rest through a distance of 200 m and acquires a speed of 50 m/s. Work done against friction of air is (Take g = 10 m//s^2)
Answer» 700 J 1250 J 750 J 1960 J SOLUTION :PE lost = `mgh = 1 xx 10 xx 200 = 2000 J` KE gained = `1/2 mv^2 = 1/2 xx 1 xx (50)^2 = 1250 J` Work done against friction of AIR = `2000 J - 1250 J = 750 J` .