A model rocket is launched straight upward with an initial speed of 60.0 m/s. It accelerates with a constant upward acceleration of 2.00 m/s2 until its engines stop at an altitude of 130 m.

Question

A model rocket is launched straight upward with an initial speed of 60.0 m/s. It accelerates with a constant upward acceleration of 2.00 m/s2 until its engines stop at an altitude of 130 m.
(a) What is the maximum height reached by the rocket? 
  m

(b) How long after lift-off does the rocket reach its maximum height? 
  s

(c) How long is the rocket in the air?
  s

bobpursley · Answer

I would use energy concepts.

Launch energy: 1/2 m 60^2
engine energy: F*d=ma*d=m*2*130
work done on gravity at the top: mg*h

mg*h=1/2 m 60^2+m*260 solve for h.

For b) find time to the rocket burns out, then add the glide time to the final heights.

c. Add the fall time.

frank · Answer

could you possibly explain A. im still not understanding it.

frank · Answer

I solved for h and got 210.2. What am I doing wrong?