Physics work energy throrem

Question

ball of mass m has a gravitational potential energy of 200 J when held at a height h above the Earth's surface. The ball is now released from rest from this height h. In the absence of air resistance, the kinetic energy of the ball when it has a fallen a distance h/4 is

(A) 50 J

(B) 100 J

(C

Answer 1

Assuming that you know Gravitational Potential Energy (U) =mgh 

Applying Energy Conservation;

K_i+ V_i = K_f + U_f

Since initially body at rest so, K_i =0

0+200= K_f + mg(h-h/4)

200= K_f  + 3/4(mgh)-------------(i)

And since mgh= 200

Therefore 3/4 mgh = 150

On putting value in equation (i)

we get K_f  = 50J