At void, an object with velocity v, mass m collides with an object with the same mass m at rest. Let's assume that they were connected to each other(the instant after the collision). then it would be double the mass and half the velocity $E = \frac{1}{2}2m(\frac{v}{2})^2 = \frac{1}{4}mv^2$
There is no PE in the object.
Why would it lose KE and Where does the KE go?
