Question

Jules kicks a soccer ball off the ground and into the air with an initial velocity of 25 feet per second. Assume the starting height of the ball is 0 feet. Approximately, how long does it take until the soccer ball hits the ground again?

0.6 sec

0.8 sec

1.6 secs

2.8 secs

Answer 1

Please help if you know! :D

Answer 2

Oh, ok, thx. :)

Answer 3

we have a quadratic equation formula, we have to use. :)

Answer 4

Do you have a quadratic equation for the height of the ball at some time "t"? Like a function h(t) = ...

Answer 5

Hmmm...let me see. :)

Answer 6

I don't know, but I am preety sure you are right.

Answer 7

What class is this?

Answer 8

Algebra 1. :) I just looked up on Google, and they said the answer was B. But I am not sure. :)

Answer 9

I would have said (c)... here's why:

acceleration of gravity = 32.174 feet per second squared

velocity 1 = 25 feet per second
velocity 2 = -25 feet per second (speed of ball when it hits the ground is the same as when it was kicked, but opposite direction)

so time = (25 - (-25)) / 32.174
= 50 / 32.174
= 1.554 seconds

Answer 10

I'm a little surprised they gave you this question in algebra 1.

If they had given you the formula for the balls height as something like:

h(t) = At^2 + Bt + C

Then you could ask and answer, if the height is zero when it hits the ground, then what is the time, t?

0 = At^2 + Bt + C

Then you could use the quadratic formula.

Answer 11

But requires a height formula... you could derive that formula from the initial velocity, but that might require some calculus :)

Answer 12

Oh, wow, I do not know what to put!

Answer 13

Thx for your help!! :)

Answer 14

I might have messed it up... I was working from memory, but 0.8 could be right.

Answer 15

Yeah, I think I messed it up above.

The equation is h(t) = at^2 + vt + d
where a = acceleration of gravity = - 32.174 ft/sec^2
v = 25 feet/sec
d = starting height = 0
and h(t) = 0 when the ball hits the ground.

So, 0 = - 32.174t^2 + 25t + 0

You can use the quadratic formula on that if you want, or you can solve like this:

0 = - 32.174t^2 + 25t
0 = t ( -32.174t + 25)

So, one solution of that is t = 0, corresponding to the initial time when the ball is kicked.

The other time is: 25 = 32.174t
t = 25/32.174 = 0.777 seconds
or approximately 0.8 seconds.

Answer 16

OMG, thx! That is what Google said. :)

Answer 17

Yes, but I've found other explanations that said what I said first. I'm confusing myself...

Answer 18

LOL, Algebra is confusing. :)

Answer 19

I would go with 0.8, but this is better taught as a physics question. Sorry I wasn't more help!

Answer 20

it s okay! I will go with that, and let youknow if it was right. :)