A model rocket Is launched from a height of 50ft. The formula h=-16t^2+70t +50 describes the rocket's height,h,in feet seconds after it was launched. How long will it take the rocket to reach to reachthe ground?

Answer 1

When it's at the ground h = 0

-16t^2+70t+50 = 0

using the quadratic formula
t=5
t=-.625

t cannot be negative, so t=5s is the correct answer.

http://www.regentsprep.org/regents/math/algtrig/ate3/quadformula.htm