. During the St. Patâs celebrations, for reasons we will not discuss, a person is driving a car of mass m and speed v the wrong way out of the Physics Department parking lot, in the positive ydirection. At the same time, a law-abiding citizen in a pickup truck of mass M is traveling at unknown speed on Pine Street which makes an angle θ with the x-axis. The car and the truck collide and stick together. The fused wreckage is skidding in the positive x-direction along the horizontal road surface for a distance D until it comes to a stop. Derive an expression for the coefficient of kinetic friction, µ, between wreckage and road, in terms of m, M , v, D , θ and constants. You may use, without proof, that the normal force magnitude is equal to the weight magnitude. (No people have been harmed in the creation of this test problem.)