anonymous one year ago A volleyball is thrown up in the air with initial velocity of 8.2m/s. How long does it take the ball to reach maximum height? help please!

1. zephyr141

do you know the kinematic equations?

2. zephyr141

if you don't just google them.

3. anonymous

well i was given 3 to choose from. and i know im looking for the time. so im going to assume i have to use either, g=vf-vi/ t or y= vi(t)+1/2 (g) (t)^2

4. zephyr141

$1:d=v_0t+\frac{1}{2}at^2$$2:v^2=v_0^2+2ad$$3:v=v_0+at$$4:d=\frac{v_0+v}{2}t$

5. zephyr141

i would use number 3.

6. anonymous

oh then idk what i just gave you because thats like completely different but ok so how would i get t by itself

7. zephyr141

$0=8.2+(-9.8)t$$-8.2=(-9.8)t$$\frac{-8.2}{-9.8}=t$$0.84s=t$

8. zephyr141

subtract 8.2 from both sides. then divide both sides by (-9.8) to isolate t.

9. zephyr141

the first equation you gave me looks a lot like equation 4 that i gave you.

10. anonymous

oh ok

11. anonymous

so then how do i know what the total time was that the ball was in the air?

12. zephyr141

well we found the time it took to get up to it's max height. assuming that nothing changes in it's descent then it should be the same amount of time on the way back down. |dw:1444277213628:dw|

13. zephyr141

so you can figure that one out. you can do it!

14. anonymous

lol so i just add them then? right?

15. zephyr141

yep. that's the total time in flight. of course if the final resting point is any number of feet/meters or whatever measurement lesser or greater than it's original values then the problem gets a little harder.

16. anonymous

ahhhh i got you now. thanks!

17. zephyr141

don't forget to medal. lol. good luck on any future problems.