Please explain this and tell which formula will be applied and how to get answer step by step

AP 6. A 2.00 kg rock is dropped from the top of a 30.0 m high building. Calculate the ball's momentum at the time that it strikes the ground. 7. A 1.00 kg rock is thrown up into the air from ground level at a speed of 8.00 m/s. The ball travels up night to a maximum height, then returns to the ground. Calculate the rock's momentum as it strikes the ground. 8. A 1.50 kg rock is thrown up into the air from ground level, reaches a maximum height of 7.00 m, then returns to the ground. Calculate the rock's momentum as it strikes the ground