# Thread: Determing Acceleration, Tension

1. ## Determing Acceleration, Tension

I had a wheel.
I hung five weights of known masses from the wheel, and these fell a known distance in a known time.
I also hung a weight and added mass until it just began to move, so I know the frictional force the wheel must overcome to spin.

I feel so silly asking it, but how can I find
the acceleration of the falling masses?
the tension in the string?

2. ## Acceleration and tension

Hello Oijl
Originally Posted by Oijl
I had a wheel.
I hung five weights of known masses from the wheel, and these fell a known distance in a known time.
I also hung a weight and added mass until it just began to move, so I know the frictional force the wheel must overcome to spin.

I feel so silly asking it, but how can I find
the acceleration of the falling masses?
the tension in the string?
You don't give us enough detail for me to give you a specific answer, but these are the principles you should use:

1. If you know that a body starts with velocity $u$, and it travels a distance $s$, in time $t$, with an acceleration $a$, then

$s = ut +\tfrac{1}{2}at^2$

Obviously, if your weights start from rest, then $u = 0$, and the equation is simply

$s = \tfrac{1}{2}at^2$

2. If the tension in the string is $T$ (upwards) and there is a weight force $mg$ downwards, and the acceleration is $a$ (downwards) then

Resolve downwards: $mg-T = ma$

If you know $a$ and $m$, this will give you the tension, $T$.

Grandad