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Mechanics
 Aim: to estimate the Coefficients of Friction for two solid surfaces If necessary, see the coefficients of friction and friction, example. Dynamic Friction Method It is suggested that the force of friction be measured using apparatus as shown below. We will be finding the coefficient of friction between the wood or metal (or whatever) and the surface of the bench (or whatever covers the bench). For a range of loads, find the force, mg which is needed to keep the object moving at approximately constant speed once you have given it a small push to start it moving. Why do you need to give it a push? Find the coefficient of dynamic friction from a suitable graph. Static Friction Put the object on the surface and slowly increase the angle of the slope. Find the maximum angle at which the object remains stationary. Just before the object starts to slip down the slope, the forces acting on it are in equilibrium. Therefore, the magnitude of Ff must be equal to a component of mg and the magnitude of R must be equal to another component of mg. Using these ideas you should be able to show that the coefficient of static friction μs is given by where θ is the maximum angle at which the body remained stationary.

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