# Help with physics problem please.

miamirulz29
Projectile Motion and Level Horizontal Range.

## Homework Statement

The acceleration of gravity is 32ft/s ^2.
If a pitch were thrown horizontally with a velocity of 96.9 mi/h, how far would the ball fall vertically by the time it reached home plate, 60ft away. Answer in units of ft.
So speed is 142.12 ft/s.

## Homework Equations

Vx = Vxo + Axt
Y= Yo + VyoT + 1/2AyT^2 or Vy^2 = Vyo^2 + 2Ay(Y-Yo)

For the second equation, don't know which one to use.

## The Attempt at a Solution

I got the time it took to reach 60 feet by using the first equation. T= 4.441. I don't know where to go from there. I think I use this equation: Y= Yo + VyoT + 1/2AyT^2

but I'm not sure. Any help would be appreciated greatly.

Edit: actually t= .422 seconds.

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## Answers and Replies

miamirulz29
Anybody?

harvellt
sorry

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miamirulz29
I'm not sure what you are asking. Sorry to be such a pain.

harvellt
Sorry, ok so you know how long it takes for the ball to get from release to home. It travels a distance in the -y direction in that time. Thats what your looking for.

miamirulz29
using this equation: Y= Yo + VyoT + 1/2AyT^2, I got 57.151. That definitely is not right or is it?

harvellt
probably not what are you using for Vy at t=0? and if y=0 at the pitchers release what direction is acceleration in the y direction?

miamirulz29
I cannot figure out this problem. Maybe I got the time wrong. I don't even know what I'm looking for. Can somebody please clarify some stuff for me. I just want to know how to do it.

miamirulz29
probably not what are you using for Vy at t=0?

You mean Vyo, I used the original speed the ball was thrown, 142.12 feet/s. Is that wrong?

harvellt
yes that is wrong. That is the Vox, what is the Voy if the ball is thrown horizontally?

miamirulz29
zero?

harvellt
yep, and then what is the acceleration of the ball?

miamirulz29
OMG I just got it. Voy is 0! So it is -y = 1/2 (32) (.422)^2. Which gives me 2.849. Which is right in the computer. Thank you for your help!

harvellt
no prob!