posted by Anon on .
A vacant, 1560 kg car begins from rest and rolls 46 meters down an inclined plateau before rolling off the edge and crashing into the sea below. The plateau is at a constant downward angle of 12.4 degrees with the horizontal. The coefficient of rolling friction between the car and the plateau is 0.125 and the edge of the plateau is 55 meters above the sea.
At what rate was the car accelerating as it rolled down the plateau?
This is one of those problems where you have to weed out or ignore the information you don't need.
The component of the weight force along the incline is M g sin 12.4. Opposed to that is the rolling friction, which is M g cos 12.4 * 0.125. Subtract the second number from the first for the net force that causes acceleration. Then divide by the mass M for the acceleration, a. Since mass cancels out,
a = g (sin 12.4 - 0.125 cos 12.4)