Question

Suppose a football is kicked from the ground and its height, h, in feet above the ground is given by h = -3.9t2 + 15.6t.

The time, t, represents the number of seconds after the ball is kicked. At what time does the football hit the ground?

Answer 1

The ball starts at ground level before being kicked, then hits the ground again at t = 4 seconds.

Step-by-step explanation:

Given : Suppose a football is kicked from the ground and its height, h, in feet above the ground is given by
`h = -3.9t^2 + 15.6t`. The time, t, represents the number of seconds after the ball is kicked.

To find : At what time does the football hit the ground?

Solution :

The equation of kicked a football with height and time is given by,

`h = -3.9t^2 + 15.6t`

We have to find at what time the ball hit the ground which means the height of ball became zero.

So, Substitute h=0 in the equation

`0= -3.9t^2 + 15.6t`

`t(-3.9t+ 15.6)=0`

Either t=0 or
`-3.9t+ 15.6=0`

`3.9t=15.6`

`t=(15.6)/(3.9)`

`t=4`

The ball starts at ground level before being kicked, then hits the ground again at t = 4 seconds.