(II) Police investigators, examining the scene of an accident involving two cars, measure 72-m-long skid marks of one of the cars, which nearly came to a stop before colliding. The coefficient of kinetic friction between rubber and the pavement is about 0.80. Estimate the initial speed of that car assuming a level road.
Solution 70GP: The coefficient of kinetic friction come into play when the object is set into motion, that is there is relative motion between between the two surface, and we have calculate initial speed of the car. Step 1 of 3 Concept: Newton’s second law: The force F acts on mass m produces an acceleration a in the object. Mathematically, F=ma. Frictional force also acts on the surface of the bodies in contact whenever their is relative motion between between the two bodies.