- #1
GZM
- 14
- 1
Homework Statement
Problem : During your summer internship for an aerospace company, you are asked to design a small research rocket. The rocket is to be launched from rest from the earth's surface and is to reach a maximum height of 990 m above the earth's surface. The rocket's engines give the rocket an upward acceleration of 16.0 m/s2 during the time T that they fire. After the engines shut off, the rocket is in free fall. Ignore air resistance.
What it asks for : What must be the value of T in order for the rocket to reach the required altitude?
Homework Equations
Kinematic equations : d=vi*t+(1/2)*a*t^2
vf^2 = vi ^2 + 2*a*d
vf = vi + at
The Attempt at a Solution
My attempt at the solution was that i thought at the apex of the height 990 m the final velocity would be 0,
since they give us acceleration, distance and I can guess that vf is zero
Step 1 ) i used the equation vf = vi+at, i would solve for t and it would be t = -Vi/16
Step 2 ) i would use vf^2 = vi^2 + 2ad but when I isolate Vi it would become negative and I can't square root, so
I am stuck at this step, please help