Question

A helicopter is h metres above the ground at a time of t seconds. The height of this helicopter during a helicopter ride can be modelled by; h = (-16t^2 + 8t +48)

Find the time in seconds, for the helicopter to reach the ground.

Answer 1

It will take the chopper 2 seconds to reach the ground

Explanation:

When the helicopter reaches the ground , then it is at height zero.

Thus, we equate the modeled equation to zero.

0 = -16t^2 + 8t + 48

This is same as;

16t^2 -8t -48 = 0

We divide through by 8

2t^2 - t - 6 = 0

2t^2 - 4t + 3t - 6 = 0

2t( t- 2) +3 (t -2) = 0

(2t + 3)(t-2) = 0

2t + 3 = 0 or t - 2 = 0

2t = -3 or t = 2

t = -3/2 or t = 2

t = -1.5 or t = 2

Since time cannot be negative, we select t = 2 and ignore t = -1.5

Thus, it will take the chopper 2 seconds to reach the ground