- #1

Mad_Eye

- 69

- 0

take a sphere rotating around some far axis

F

_{T}=ma

_{T}

F

_{T}=m * ALPHA * R

multiple by R

tau = mR

^{2}* ALPHA

and we can say it true for every limit mass in a body.

so

sigma tau = sigma (mR

^{2}) * ALPHA

sigma tau = I * ALPHA

internal torque=0

thus, sigma tau = sigma external tau

fine, i get it, i think.

but what if we didn't multiple by R?

let's return to here

F

_{T}=m * ALPHA * R

and do not multiple by R

now as far as i see it, this is also true for every limit mass on a body, so

sigma F

_{T}= sigma (mr) * ALPHA

internal forces=0 (?)

thus

sigma external F

_{T}= F

_{T}= sigma (mr) * ALPHA

but that just doest make sense... since it as though it doesn't matter where the force is applied...

thanks a lot for helping...