What will happen to the kinetic energy of a body if its velocity is halved ?

As known Kinetic Energy $K=\frac{1}{2}mv^2$

Where $m\rightarrow$ mass of a body

$v\rightarrow$ velocity of the body

If half the velocity then the velocity becomes $\frac{v}{2}$

Then kinetic energy $K=\frac{1}{2}m( \frac{v}{2})^2$

$=\frac{1}{4}\times\frac{1}{2}mv^2$

Thus, kinetic energy will remain one fourth when the velocity is halved.