Solve the all parts of following question:
Question: A rock is tossed straight up with a velocity of 21m/s When it returns, it falls into a hole 10m deep.
Part I: What is the rock's velocity as it hits the bottom of the hole?
Part II: How long is the rock in the air, from the instant it is released until it hits the bottom of the hole?
I need help to find the rock's velocity as it hits the bottom of the hole.