Question

A rubber block weighing 60. newtons is resting on a horizontal surface of dry asphalt. what is magnitude of the minimum force needed to start the rubber block moving across the dry asphalt?

Answer 1

First you must look for the coefficient of friction of the dry asphalt. For this case, searching in google, the value is 0.85. Then, you must find the normal force by making a free-body diagram. In the diagram, you sum up forces in vertical direction and find that the normal force is 60N. Then, by sum of forces in a horizontal direction, the friction force will be given by:F = (60) * (0.85) = 51N.51N is the magnitude of the minimum force needed to start the rubber block moving across the dry asphalt