Vf (final velocity)

if i'm conducting an experiment (like letting a small toy car run from start, time it from start to the certain point that i want to know Vf(final velocity))
what formula should i use to know Vf? should i know the accelration first but how? i'm trying to use the formula
a = (Vo + Vf)/t where
a=acceleration
Vo=Inital velocity in (meters/s)
Vf=Final velocity in meters per second
t=time in seconds
not constant acceleration
but still a liitle bit confused of what to do
thanks
(sorry for my wrong formula of acceleration before)
Ron

Will the car have a constant acceleration?

How you will measure it?

Your first equation for acceleration (i.e., a = (Vo + Vf)/2 ) just doesn't make sense. Why don't you write the units for velocity and see whether you end up with the correct units for acceleration doing it that way?

John

If the car has a constant acceleration then you can use:

s=0.5*a*(t^2)

to find the distance

Otherwise you need to make a circuit which will measure the speed of the car at any instant in time and integrate it as to find the distance (s).

(Vf)2-(Vi)2 = 2*a*S

Where Vf = Final Velocity
Vi=Initial Velocity(=0,if it starts from rest)
a= acceleration
S= distance covered.

S=[(Vi)*t]+[.5*a*t2]

Where t= time of journey..

Using these you can calculate the required parameters...provided,the acceleration in uniform..

If its not uniform and a variable one,Use differential form..

a=dv/dt=d/dt(v) where v=velocity,in terms of time

Hope this would solve your problem...If you want more,do let me know...

Cheers,
hanu