- #1
Mad_Eye
- 69
- 0
the proof of second law of Newton for rotation goes like this:
take a sphere rotating around some far axis
FT=maT
FT=m * ALPHA * R
multiple by R
tau = mR2 * ALPHA
and we can say it true for every limit mass in a body.
so
sigma tau = sigma (mR2) * 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
FT=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 FT = sigma (mr) * ALPHA
internal forces=0 (?)
thus
sigma external FT = FT = 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...
take a sphere rotating around some far axis
FT=maT
FT=m * ALPHA * R
multiple by R
tau = mR2 * ALPHA
and we can say it true for every limit mass in a body.
so
sigma tau = sigma (mR2) * 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
FT=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 FT = sigma (mr) * ALPHA
internal forces=0 (?)
thus
sigma external FT = FT = 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...