Net force from a varying speed non-uniform rotating wheel?

[NotASmurf]

If we have a circle rotating then a force v^2/r is produced but no net directional force exists as it cancels.
But if the wheel was not uniform in mass ie not rotating around its centre of mass AND the speed changes over time as a function of the "wheel"'s rotation angle could a net force be produced in a direction of choice? If not then could it be achieved by doing the above AND varying the centre of mass?

 

[mfb]

If we have a circle rotating then a force v^2/r is produced but no net directional force exists as it cancels.

That is not a force, it is an acceleration. More precisely, it is the magnitude of the acceleration of an object rotating with the disk at radius r.

If the center of mass is not at the rotation axis you need a time-dependent net force on the object to have it rotating around its off-center rotation axis, but integrated over one rotation the average force is zero.

Accelerating the system doesn't change anything, shifting masses around just makes the calculations more complicated, and overall momentum and energy are conserved exactly.

 

[berkeman]

If we have a circle rotating then a force v^2/r is produced but no net directional force exists as it cancels.
But if the wheel was not uniform in mass ie not rotating around its centre of mass AND the speed changes over time as a function of the "wheel"'s rotation angle could a net force be produced in a direction of choice? If not then could it be achieved by doing the above AND varying the centre of mass?

It sounds like you are trying to discuss a Reactionless Drive mechanism, which along with PMMs and Over-Unity mechanisms, we do not take the time to discuss. Is that what you are asking about?

https://en.wikipedia.org/wiki/Reactionless_drive

 

[NotASmurf]

I know this post seems stupid, only asking because our physics TA (in honours and spends too much of his clean energy optimization funding on rent) said that this was "an active area of research".

Oh, is the reason this isn't possible because (sorry for no latex, my keyboard is broken, on screen keyboard is effort and latex takes more typing):

e=.5mv^2, f=ma

f=m. ∂/∂t [2e/m]^0.5

for a net force we need:
Σf=0
to not be true.

thus
Σf≠0 ⇒ f≠[2]^0.5 * ∂/∂t * [m^-0.5 * e^0.5 * m] ⇒ 0 ≠ Σ(e^.5)(m^[-3/2]) ⇒Σe≠0

So if he was right energy wouldn't be conserved?

 

[berkeman]

As I said, we don't waste time discussing such things here. Thread is closed.

EDIT / ADD:

So if he was right energy wouldn't be conserved?

There are many reasons it cannot work, energy conservation could be one of them. Please follow the links in the Wikipedia article for more reasons it cannot work.