Correct Answer to Question 3

To find the acceleration of the car, we must find the forces acting on the car. Their vector sum F then gives the acceleration from F = Ma.

The diagram shows the three forces on the car: the weight W (due to the earth), the normal force N (due to the road) and a northward force F (3300 N) due to the road.

The forces W and N are equal and opposite, so their sum is zero. The resultant force is just F. Hence, F = M a becomes 3300 = 1100 * a and a = 3 m/s^2 northward.

Notice that forces exerted by the car on the road do not enter the problem. They must be present but they would contribute to the motion (if any) of the road, not to the motion of the car.

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