Hi everyone, A question just pop up from my head. Imagine a rigid body cylinder is rotating freely about its z-axis with a known angular velocity. Let's say the whole system is frictionless. How can I get the value of the torque at the center of the z-axis? Is the net force on this free rotational body equals zero even though it is rotating? Why I have a thought of it is because I want to know if the spinning wheel of a car will apply any torque to the drive shaft if the car is coasting.