# Finding ball velocity using time

• Oct 8th 2011, 08:17 AM
vaironxxrd
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 $\frac{20cm}{.97s}$ which is $20.62\frac{cm}{s}$

Therefore the average velocity should be Finalvelocity/2

Average velocity = $10.31\frac{cm}{s}$
• Oct 8th 2011, 09:03 AM
skeeter
Re: Finding ball velocity using time
try again ...

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

for constant acceleration ...

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

since the ball starts from rest ...

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

$2v_{avg} = v_f$
• Oct 8th 2011, 11:03 AM
vaironxxrd
Re: Finding ball velocity using time
Quote:

Originally Posted by skeeter
try again ...

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

for constant acceleration ...

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

since the ball starts from rest ...

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

$2v_{avg} = v_f$

Thanks allot skeeter.