<< Mentor Note -- this re-post is okay. This turns out to be a personal project, not schoolwork >> Because my previous post was removed, I would like to clarify that this is a personal project, not a school project. I have been working on a design similar to a clutch which would be used for a bicycle to automatically store and release energy from a spring. I have finished the basic design, and I am now working on writing equations for it. However, I am having some difficulty for certain parts such as the one below. Two friction discs are rotating with different angular velocities and different torques. The discs come in contact with one another and press together with a certain amount of force. If you know: the initial angular velocity and torque of both discs the radius of both discs the normal force pressing the discs together the coefficient of friction for the friction surfaces, both static and kinetic could you find the change in the torque and angular velocity of both discs? If possible, how would one write an equation to solve this? I am not asking for the exact equation but simply the method one would go about to find it. I have attempted to solve this using arithmetic. However, based on similar problems, it seems to require calculus, which I have never been taught.