Question

A toy car launched into the air has a height (h feet) at any given time (t second) as h= -16t + 160t until it hits the ground. At what times is it at a height of 9 feet above the ground?

Answer 1

t = 0.0625

Explanation:

Given that,

Height, h = -16t + 160t

To obtain time,t at height,h = 9feet

We substitute h = 9 into the given equation to have:

9 = - 16t + 160t

: 9 = 144t

t = 9/ 144 = 0.0625

Answer 2

`t_(1) \approx 9.943\,s` and
`t_(2) \approx 0.057\,s`

Explanation:

The following polynomial is needed to be solved:

`-16\cdot t^(2) + 160\cdot t - 9 = 0`

The roots are found by means of the General Equation for Second-Order Polynomials:

`t_(1) \approx 9.943\,s` and
`t_(2) \approx 0.057\,s`

Physically speaking, both solutions are reasonable.