Question

If a football player passes a football from 4 feet off the ground with an initial velocity of 36 feet per second, how long will it take the football to hit the ground? Use the equation h = −16t2 + 36t + 4.

Answer 1

(9 + sqrt(97))/8 C is the closest answer - probably just ignore the fact that - will give a negative result

Answer 2

it takes 2.4 seconds for the football to hit the ground

Explanation:

h = −16t^2 + 36t + 4

When the ball reaches the ground the height becomes 0

so we replace h with 0

0 = −16t^2 + 36t + 4

Apply quadratic formula to solve for t

`t=(-b+-√(b^2-4ac) )/(2a)`

a= -16, b= 36 and c= 4

`t=(-36+-√(36^2-4(-16)(4)))/(2(-16))`

`t=(-36+-√(1552))/(-32)`

`t=(-36+-4√(97))/(-32)`

`t=(9+-√(97))/(8)`

t= -0.106 and t= 2.356

time t cannot be negative

so it takes 2.4 seconds for the football to hit the ground