Answer:
m v1 = (m + M) v2
v2 = m v1 / (m + M)
v2 = 7 * 74 / (74 + 65)
3.73 m/s
74 kg is too heavy for the cannonball (over 150 lbs)
The ball's vertical position
in the air at time
is

The ball is at its original height when
, which happens at


Meanwhile, the ball's horizontal position
at time
is

So when the ball reaches its original height a second time, the ball will have traveled a horizontal distance of

(which you might recognize as the formula for the range of a projectile)
To reach a distance of
, the initial speed
would be

Kinetic energy is energy in motion and potential energy is stored energy
During a phase change, the temperature remains constant. obviously all the heat is used in phase transformation.