Answer:
C) Its momentum is not conserved, but its mechanical energy is conserved.
Explanation:
There is no air resistance acting on the ball: this means that there are only conservative forces acting on the ball, therefore the total mechanical energy of the ball is conserved.
The total mechanical energy is defined as
where
U is the gravitational potential energy
K is the kinetic energy
The gravitational potential energy is given by:
where m is the mass, g the acceleration of gravity, h the heigth - since the height change, U changes as well, so the potential energy is not conserved.
The kinetic energy is given by
where v is the speed of the ball: as the ball rises, its speed decreases, so the kinetic energy is not conserved as well.
The momentum of the ball is given by:
As we stated above, the speed of the ball is decreasing, so v is decreasing, and this means that the momentum is also not conserved.
So the only correct choice is
C) Its momentum is not conserved, but its mechanical energy is conserved.