Question

A model rocket is launched with an initial upward velocity of67m/s . The rocket's height h (in meters) aftert seconds is given by the following. h=67t-5t^(2)

Find all values of for which the rocket's height is 30 meters
Round your answer(s) to the nearest hundredth.
(If there is more than one answer, use the "or" button.)

Answer 1

30 = 67t - 5t^2
5t^2 -67t + 30 = 0

a = 5, b = -67, c = 30

67 +/- root (67^2 - 4*5*30) / 2*5
67 +/- root (3889) / 10
67 +/- 62.36 / 10

(67 - 62.36) / 10 = 0.46 seconds

(67 + 62.36) / 10 = 12.94 seconds