Does a bike chain apply torque?

Answer 1

Yes. The chain applies a linear force to the cog on the rear wheel. It pulls it forward when we "go" on the bike. The teeth on the cog, where the linear force is applied, are arranged around the center of rotation of the rear axle. This applies a force to the axle that is "off center" with the axis of rotation of the axle. The axle is perpendicular to the plane of the cog, and this is true. But the actual "pull" of the chain is on the back teeth and the top teeth of the cog. The axle cannot move forward because it is fixed, but the axle can rotate because a good portion of the force applied to it causes it to turn. A bike chain applies torque to the rear wheel. Torque is a momentary force, and in the case of the bike chain, a continuous series of moments of force applied to the rear wheel by the chain turns the rear wheel. Another way to look at the problem is to consider that the feet move up and down (and a little forward and back) on the pedals. The crank and chain ring turn around. The chain moves in a line or displays linear motion, and the rear wheel displays rotary motion. The transition from linear motion to rotary motion applies the idea of torque.