A catapult launches a test rocket vertically upward from a

Question

Compute all parts of given question:

Question: A catapult launches a test rocket vertically upward from a well, giving the rocket an initial speed of 80.8 m/s at ground level. The engines then fire, and the rocket accelerate upward at 4.20 m/s2 until it reaches an altitude of 990 m. At that point its engines fail, and the rocket goes into free fall, with an acceleration of 9.80 m/s2. (You will need to consider the motion while the engine is operating and the free-fall motion separately.)

Part I: For what time interval is the rocket in motion above the ground?

s

Part II: What is its maximum altitude?

km

Part III: What is its velocity just before it hits the ground?

m/s

This is a physic question, reply as soon as possible. Thanks.