SOLUTION: A model rocket is shot into the air and its path is approximated by h = -5t^2 + 30t where h is the height of the rocket above the ground in metres and t is the elapsed time in seco

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: A model rocket is shot into the air and its path is approximated by h = -5t^2 + 30t where h is the height of the rocket above the ground in metres and t is the elapsed time in seco      Log On


   

Question 210707: A model rocket is shot into the air and its path is approximated by h = -5t^2 + 30t where h is the height of the rocket above the ground in metres and t is the elapsed time in seconds. When will the rocket hit the ground?
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
When the rocket hits the ground again after taking off, h will be zero, so set the equation equal to zero and solve for t.
-5t%5E2%2B30t+=+0 Factor a t from the binomial on the left side.
t%28-5t%2B30%29+=+0
t+=+0 or:
-5t%2B30+=+0 Add 5t to both sides.
30+=+5t Divide both sides by 5.
6+=+t
The rocket will hit the ground in 6 seconds.