Question

A body of mass 2 kg is thrown up vertically with K.E. of 490 joules. If the acceleration due to gravity is 9.8 m/s², the height at which the K.E of the body becomes half of its original value is given by :

(A) 50m 

(B) 12. 5m

(C) 25m 

(D) 10m.

Answer 1

Answer is (B) 12. 5m

When he kinetic energy is halved, the potential energy s equal to the kinetic energy. That is mgh = (490/2)J = 245 J. this gives h =12.5 m.