A model rocket is launched off the top of a platform. The height of the rocket is given by the function h(t) = -4.9t2 + 86t + 2.1, where h(t) is the height in metres and t is the time in seconds.

a) When will the rocket’s height be 200 m?

b) How long will it take for the rocket to reach the ground?

Julius
Apr 4, 2017

#1**+2 **

a) 200 = -4.9t^2 + 86t + 2.1 subtract 200 from both sides

0 = -4.9t^2 + 86t - 197.9 using the quadratic formula.....we have

t = [ -86 ± √ [ (86)^2 - 4 ( -4.9) (-197.9) ] ] / (2 * - 4.9)

Evaluating this.....we have that .... t ≈ 2.7 seconds and t ≈ 14.8 seconds

b) 0 = -4.9t^2 + 86t + 2.1

Again, using the quadratic formula we have ≈ 17.575 seconds

CPhill
Apr 4, 2017