# Velocity in free fall

1. Feb 10, 2009

### Makaroon

1. The problem statement, all variables and given/known data
A rock thrown straight up climbs for 2.50 s, then falls to the ground. Neglecting air resistance, with what velocity did the rock strike the ground?

2. Relevant equations
well we are looking for v=?
we have:
t=2.50 s
and g=9.8
^do we need gravity? yes, right? =S

3. The attempt at a solution
v= d/t
well we only have the time.
so we have to look for the distance... but the distance is ?
do we have to calculate another equation.

thanks.

2. Feb 10, 2009

### tiny-tim

Hi Makaroon!
You have the initial speed (zero), and the time, and you want the final speed.

So which https://www.physicsforums.com/library.php?do=view_item&itemid=204" equation should you use?

Last edited by a moderator: Apr 24, 2017
3. Feb 10, 2009

### Makaroon

Re: Velocity

hi!! would this one be it?
v= u +at
and then resulting to be 24.5.

Last edited by a moderator: Apr 24, 2017
4. Feb 10, 2009

### tiny-tim

Yup!

(moral: write out all the letters you have … in this case u v a and t … and then choose an equation to fit )​

5. Feb 10, 2009

### Makaroon

Re: Velocity

That's true.
Thank you so much!!
I truly appreciate it!!! =]