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.

Question

matt101 · Answer

When the football hits the ground, h=0. Knowing this, we can find the time it took for the ball to hit the ground:

$$h= -16t^2 + 36t + 4$$$$0= -16t^2 + 36t + 4$$$$0= -4t^2 + 9t + 1$$
Using the quadratic formula, we get two values for t: -0.11 and 2.36. Having a negative time doesn't make sense - therefore the answer is 2.36 seconds!

anonymous · Answer

thanks a lot I appreciate your help

anonymous · Answer

quantity of 9 plus or minus square root of 65 all over 8 

 9 plus or minus square root of 65 end root over 8 

 quantity of 9 plus or minus square root of 97 all over 8	

 9 plus or minus square root of 97 end root over 8 

I dont understand because those are the answer choices

matt101 · Answer

I got the answers above because I just solved the quadratic formula using a calculator.

If you write out the quadratic formula and sub in your numbers but don't solve, you'll find that your answer is one of the ones you just listed!

anonymous · Answer

alright I see thanks