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Friction Example
 A body rests on a horizontal piece of metal. The coefficients of friction between the body and the metal surface are µs = 0.3 and µd = 0.22 One end of the piece of metal is lifted up. a) What is maximum angle of inclination for which will the body will not slide down the slope? b) What will be the acceleration of the body down the slope once it as started moving? Assume that the angle of the slope is equal to (or very close to) the maximum angle calculated in part a). In the following statements we consider just the magnitudes of the forces. a) The body will not slide down the slope as long as Therefore, at the maximum angle Also, as the forces acting perpendicular to the slope are in equilibrium, we have and, from the definition of the coefficient of friction, we have Dividing the first equation by the second gives so which gives maximum angle of slope about 16.7° b) The net force acting down the slope is equal to the component of the force of gravity acting down the slope minus the force of friction. and as the forces acting perpendicular to the slope are still in equilibrium, we have Therefore and, as acceleration = force/mass, we have which gives a = 4.88ms-2
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