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Buckethat_fisherlad

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Thread moved from the technical forums to the schoolwork forums

**TL;DR Summary:**A force which stops a wheel/disc from rotating

Hi! I made a problem myself inspired by a typical mechanics problem, where you have two equal forces acting on each end of a wheel/disc and a third one that is suppose to stop the wheel/dic from rotating. So let me get into the details,

Let's say, we have a bicycle that is upside-down and you start to rotate the frontwheel with two equal forces on the distance R from the center of the wheel on opposite sides of the wheel (the wheel is also fixated to its center). It starts to rotate and the net-force is equal to zero (if we set the positive direction to one of the forces direction and the negative direction to the other force), whilst the torque is FR + FR = 2FR.

Now, we add a third force which is located on the arc of the wheel between the two equal forces, and call it G. The force, G, makes a 180 degree angle between itself and the radius of the wheel, and the force points away from the wheel (similar to if you had a rope attached to the arc of the wheel and you pull it to stop the wheel). Now comes the part where I'm stuck,

The net-force is now, F + G - F = 0 => G = 0 (?)

The torque is, FR + FR - G x R = 0 => lim v->180, 2F/(sin(v)) = G = infinity (?)

I know there's a detail I've missed but I really can't see it. Can any of you?