College

We appreciate your visit to If a toy rocket is launched vertically upward from ground level with an initial velocity of 128 feet per second its height tex h tex. This page offers clear insights and highlights the essential aspects of the topic. Our goal is to provide a helpful and engaging learning experience. Explore the content and find the answers you need!

If a toy rocket is launched vertically upward from ground level with an initial velocity of 128 feet per second, its height [tex]h[/tex] after [tex]t[/tex] seconds is given by the equation:

[tex]h(t) = -16t^2 + 128t \quad \text{(if air resistance is neglected).}[/tex]

a. How long will it take for the rocket to return to the ground?

b. After how many seconds will the rocket be 112 feet above the ground?

Answer :

Sure! Let's solve each part of the problem step by step.

### Part a: How long will it take for the rocket to return to the ground?

The height [tex]\( h(t) \)[/tex] of the rocket is given by the equation:
[tex]\[ h(t) = -16t^2 + 128t \][/tex]

To find the time when the rocket returns to the ground, we need to set the height [tex]\( h(t) \)[/tex] to 0 and solve for [tex]\( t \)[/tex]:
[tex]\[ -16t^2 + 128t = 0 \][/tex]

We factor out [tex]\( t \)[/tex]:
[tex]\[ t(-16t + 128) = 0 \][/tex]

This gives us two solutions:
[tex]\[ t = 0 \][/tex]
[tex]\[ -16t + 128 = 0 \][/tex]

Solving the second equation:
[tex]\[ -16t + 128 = 0 \][/tex]
[tex]\[ -16t = -128 \][/tex]
[tex]\[ t = \frac{128}{16} \][/tex]
[tex]\[ t = 8 \][/tex]

So, the rocket returns to the ground after [tex]\( t = 0 \)[/tex] seconds (the initial launch time) and [tex]\( t = 8 \)[/tex] seconds.

### Part b: After how many seconds will the rocket be 112 feet above the ground?

We need to set the height [tex]\( h(t) \)[/tex] to 112 feet and solve for [tex]\( t \)[/tex]:
[tex]\[ -16t^2 + 128t = 112 \][/tex]

Rearranging the equation:
[tex]\[ -16t^2 + 128t - 112 = 0 \][/tex]

We solve this quadratic equation using the quadratic formula [tex]\( t = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \)[/tex], where:
[tex]\[ a = -16 \][/tex]
[tex]\[ b = 128 \][/tex]
[tex]\[ c = -112 \][/tex]

Let's solve for [tex]\( t \)[/tex]:
[tex]\[ t = \frac{-128 \pm \sqrt{128^2 - 4(-16)(-112)}}{2(-16)} \][/tex]
[tex]\[ t = \frac{-128 \pm \sqrt{16384 - 7168}}{-32} \][/tex]
[tex]\[ t = \frac{-128 \pm \sqrt{9216}}{-32} \][/tex]
[tex]\[ t = \frac{-128 \pm 96}{-32} \][/tex]

This gives us two solutions:
[tex]\[ t = \frac{-128 + 96}{-32} = 1 \][/tex]
[tex]\[ t = \frac{-128 - 96}{-32} = 7 \][/tex]

So, the rocket will be 112 feet above the ground after [tex]\( t = 1 \)[/tex] second and [tex]\( t = 7 \)[/tex] seconds.

To summarize:

a. The rocket returns to the ground after 0 seconds and 8 seconds.
b. The rocket will be 112 feet above the ground after 1 second and 7 seconds.

Thanks for taking the time to read If a toy rocket is launched vertically upward from ground level with an initial velocity of 128 feet per second its height tex h tex. We hope the insights shared have been valuable and enhanced your understanding of the topic. Don�t hesitate to browse our website for more informative and engaging content!

Rewritten by : Barada