Posted by **Kyle** on Thursday, August 25, 2011 at 5:09am.

**A ball is thrown straight up in the air and passes a window 0.30s after being released. It takes 1.5s to go from the window to its maximum height and back down to the window. What was the initial velocity of the ball when it was released?**
I found where the ball would be after 0.30s:

Y = V_0 (0.30) - 1/2 (9.8) (0.30)^2

Y = (0.3) (V_0) - 0.441

Then I found where the ball would be after 1.5 which I took to the be same place as the top equation because it returns to the window:

Y = (0.30*V_0) (1.5) - 1/2 (9.8) (1.5)^2

Y = (0.45) (V_0) - 11.025

then I set the equations together and worked it out to get:

V_0 = 70.56 m/s

Is this correct?

- Physics -
**Damon**, Thursday, August 25, 2011 at 6:05am
To check it throw a ball up at 70.56 m/s

a = -9.8

v = 70.56 - 9.8 t

h = 0 + 70.56 t - 4.9 t^2

----------------------------

at the window on the way down, t = .3 + 1.5 up + 1.5 down = 3.3

v = 70.56 - 9.8(3.3) = - 38.22

h = 70.56(3.3) - 4.9(3.3)^2 = 179.5

-----------------------------------

so how long would it take to get to the window on the way up?

179.5 = 70.56 t - 4.9 t^2

no way that is t = .3 s

- Physics -
**Damon**, Thursday, August 25, 2011 at 6:15am
Now

a = -9.8

v = Vi - 9.8 t

h = 0 + Vi t - 4.9 t^2

-------------------------------

----------------------

at the top, t = .3 + 1.5/2 = 1.05

and v = 0 = Vi - 9.8(1.05)

so

Vi = 9.8(1.05) = 10.29 m/s

## Answer this Question

## Related Questions

- math - Your friend is standing below the window outside of our classroom and ...
- physics - A ball thrown straight up from the ground passes a window 5.6 m up. An...
- Physics/Science #3 - A ball is thrown vertically downward from the top of a 35.9...
- science - A ball is throen vertically downward from the rop of a 36.6 m tall ...
- Physics - Nicole throws a ball straight up. Chad watches the ball from a window ...
- Physics - Nicole throws a ball straight up.Chad watches the ball from a window ...
- physics - A ball is thrown upward. After reaching a maximum height, it continues...
- Physics - A ball is thrown vertically upward from a window with an initial ...
- physics - a ball is thrown straight up with a speed of 8.0 m/s from a third-...
- physics - A boy reaches out of a window and tosses a ball straight up with a ...

More Related Questions