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

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.

Choose one answer.

A. quantity of 9 plus or minus square root of 65 all over 8
 

B. 9 plus or minus square root of 65 end root over 8 
 

C. quantity of 9 plus or minus square root of 97 all over 8 
 

D. 9 plus or minus square root of 97 end root over 8 

Answer 1

Hi May,

 

You need to use the quadratic formula to solve this problem.

 

(-b +/- sqrt(b² - 4ac)/2a

 

where a b and c are the coefficients in the given equation

 

h = -16t² + 36t + 4

 

lets set to zero  (point when it hits the ground)

 

0 = -16t² + 36t + 4

 

now lets divide both sides of the equation by -4

 

0 = 4t² - 9t -1

 

a = 4

b = -9

c = -1

 

plug these values in the formula

 

(9 +/- sqrt(81 + 16))/8

 

(9 +/- sqrt(97))/8        (in this case we can only use the + sign since the - will give us a negative number for time

 

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

 

Hope this helps