Kinetic energy of a body is given as,
K.E = 12mv2
Let,
Mass of body = m kg
Velocity of body = v m/s
Given:
Velocity in case 2 =12×Velocity in case 1
v2=12×v1
Now, KE1=12mv21and KE2=12mv22
Substituting the values for v1 and v2 in the equation for KE,
We get, KE2=14KE1
⇒ 4KE2=KE1