# Thread: Finding ball velocity using time

1. ## Finding ball velocity using time

Hello forum, vaironxxrd here.

I had a lab which was pretty interesting to me and fun. The teacher made a ball roll from 0-20cm 5 times and then 0-40cm 5 times, and so on until the distance was 120cm.

We had 5 trials for each distance. Now I have to figure out the average and final velocity for each trial on each distance.

Just to know that I'm doing this right can someone check one of my examples?

First trial for 0-20cm.
Time = .97s

Therefore, The final velocity should be $\displaystyle \frac{20cm}{.97s}$ which is $\displaystyle 20.62\frac{cm}{s}$

Therefore the average velocity should be Finalvelocity/2

Average velocity = $\displaystyle 10.31\frac{cm}{s}$

2. ## Re: Finding ball velocity using time

try again ...

$\displaystyle \frac{\Delta x}{\Delta t} = \frac{20 \, cm}{0.97 \, s} = v_{avg}$

for constant acceleration ...

$\displaystyle v_{avg} = \frac{v_0 + v_f}{2}$

since the ball starts from rest ...

$\displaystyle v_{avg}= \frac{0 + v_f}{2}$

$\displaystyle 2v_{avg} = v_f$

3. ## Re: Finding ball velocity using time

Originally Posted by skeeter
try again ...

$\displaystyle \frac{\Delta x}{\Delta t} = \frac{20 \, cm}{0.97 \, s} = v_{avg}$

for constant acceleration ...

$\displaystyle v_{avg} = \frac{v_0 + v_f}{2}$

since the ball starts from rest ...

$\displaystyle v_{avg}= \frac{0 + v_f}{2}$

$\displaystyle 2v_{avg} = v_f$
Thanks allot skeeter.