Question

A water rocket is projected vertically upward from the ground. Its height (h) m above ground after t seconds is given by h= 20-5(t-2)². When will the rocket reach the ground?

Answer 1

Answer:

t=4 seconds

Step-by-step explanation:

The height of the water jacket that is projected vertically upward is given by the equation:

$h = 20 - 5(t - 2)^{2}$

We want to find the time that, the rocket reaches the ground.

When the rocket reaches the ground, the height , h becomes 0.

This implies that:

$20 - 5(t - 2)^{2} = 0$

Subtract 20 from both sides:

$- 5(t - 2)^{2} = - 20$

Divide through by -5;

${(t - 2)}^{2} = 4$

Take square root:

$(t - 2) = \pm \sqrt{4}$

l

$(t - 2) = \pm 2 \\ t = 2\pm 2 \\ t = 2 - 2 \: or \: t = 2 + 2 \\ t = 0 \: or \: t = 4$

Therefore the feasible time is after 4 seconds.