Can anyone help with Calculus?

Question

A projectile is shot upward form the surface of earth with an initial velocity of 120 meter per second. What is its velocity after 5 seconds? After 10 seconds?

The formula that was given is -4.9t² + v°t + s°

Answer 1

The formula is s = -4.9t^2 + 120t,
because v_0 = 120 and s_0= 0.
The velocity is ds/dt = -9.8t + 120.
When t =5, v = 120-49 = 71m/s.
When t = 10, v = 120-98 = 22m/s.