Final Answer:
The answer is (d) the vertical component of the normal force.
Step-by-step explanation:
When a car is driving on a curve, it experiences a force known as the centripetal force, which is responsible for keeping the car on the curve. This force is perpendicular to the direction of motion and is caused by the friction between the tires and the road surface. The normal force, which is the force exerted by the road on the tires, is the primary source of the centripetal force.
The normal force can be broken down into two components: the vertical component (Ny) and the horizontal component (Nx). The vertical component (Ny) is perpendicular to the road surface and is responsible for supporting the weight of the car, while the horizontal component (Nx) is parallel to the road surface and is responsible for the car’s motion.
In an unbanked curve, the horizontal component of the normal force (Nx) is zero, as the car is not tilted and the tires are not subjected to any lateral force. Therefore, the only force responsible for holding the car in the curve is the vertical component of the normal force (Ny). This force is acting downward, perpendicular to the road surface, and is equal to the weight of the car (W).
To calculate the force of the normal force, we can use the formula:
Ny = W
where W is the weight of the car.
Therefore, the force responsible for holding a car in an unbanked curve is the vertical component of the normal force (Ny), which is equal to the weight of the car (W).
Correct option is (d) the vertical component of the normal force.