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.

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

Answer 1

@campbell_st

Answer 2

@TheSmartOne

Answer 3

@sleepyjess

Answer 4

It seems like they want us to use the quadratic formula. Do you know what that is?

Answer 5

no

Answer 6

where, a, b, and c are in the the equation that has the form of

\(\Large\sf y = ax^2 +bx + c\)

Answer 7

i made it as far as finding out that t=2.36 considering it cannot be a negative

Answer 8

It would help if you could take a screenshot of the answer choices as it is hard to understand what the answer choices look like.

Also, how did you find out t = 2.36?

It doesn't seem like we can use it to help us find the answer. We need to find the exact roots by using the quadratic formula.

Answer 9

h=−16t2+36t+4

Where;
t is time in seconds.
h is height in feet.

So, you know that h=4 (height of 4 ft).

Answer 10

h=−16t2+36t+4
0=−16t2+36t+4
0=−4t2+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

Answer 11

We know that h = 4, only when t = 0.

Answer 12

Then im not sure

Answer 13

@SolomonZelman

Answer 14

Your answer is correct. However, the question is not asking for an approximate value of t. It's asking for the exact value of t. Which of those answer choices is the exact answer?

Answer 15

i am not sure im thinking A

Answer 16

or maybe c...

Answer 17

Which of those is the quadratic formula result before you find that 2.36 in the calculator?

Answer 18

A

Answer 19

Really? That comes out to about 2.13. That's not the number you gave.

Answer 20

C....

Answer 21

Are you guessing or saying? To get that number, 2.36, you had to plug the coefficients into the quadratic formula. Which one is it?

Answer 22

im saying

Answer 23

That's correct.

Answer 24

Sometimes those problems are confusing, because it's hard to tell from the given info what the initial state is.

Answer 25

very true. thank you very much.

Answer 26

As an instructor, it's often easier to just show the solution, or the solution to a similar problem. But this site doesn't allow that.

Answer 27

Again, i completely agree with that statement. i can always work my way to the correct answer if i know it first.