When both the mass and velocity of a body are doubled, the momentum of the body will be quadrupled.
The momentum of an object is given by the product of its mass (m) and velocity (v):
Momentum (p) = m * v
If the mass (m) and velocity (v) are both doubled, the new values would be 2m and 2v, respectively. Therefore, the new momentum (p') would be:
p' = (2m) * (2v) = 4mv
Comparing the new momentum (p') to the original momentum (p), we can see that p' is four times greater than p. Thus, the momentum of the body is quadrupled when both its mass and velocity are doubled.