Question

when a ball is thrown straight up at an initial velocity of 54 feet per second, The height of the ball t seconds after it is thrown is given by the function h(t)=54t-12r^2. How many seconds after the ball is thrown will it return to the ground?
A. 9.2
B. 6
C. 4.5
D. 4

Answer 1

The correct option is C. 4.5

Step-by-step explanation:

Given:

Initial velocity = 54 feet per second

Function of height is given as,

$h(t)=54t-12t^{2}$

To Find:

t = ? when the ball  will return to the ground i.e h = 0

Solution:

When the ball is return height will be zero, hence

h(t) =0

Therefore the time will be

$0=54t-12t^{2}\\\\54t=12t^{2}\\\\t=\dfrac{54}{12}=4.5\ s$

Therefore,

After 4.5 second the ball  will return to the ground.

Answer 2

Answer:

4.5

Step-by-step explanation: