A model rocket is launched straight upward. Its altitude y as a function of time is given by y=bt−ct2, where b = 80m/s , c = 4.9m/s2 , t is the time in seconds, and y is in meters.

1. Use differentiation to find a general expression for the rocket's velocity as a function of time.

2. When is the velocity zero?
Express your answer using two significant figures.

2 answers

v = dy/dt = b - 2ct
now just solve for t when v=0
-9.8t +81