Main Answer:
At the bottom of a loop, the roller coaster's normal force is zero due to balanced gravitational and centrifugal forces.c) Zero
Explanation:
When a speeding roller coaster car is at the bottom of a loop, the magnitude of the normal force exerted on the car's wheels is zero. This occurs because the centrifugal force acting on the car, directed outward from the center of the loop, exceeds the gravitational force pulling the car downward. As a result, the net force is directed upward, effectively canceling out the normal force. In this situation, the track provides the necessary centripetal force to keep the roller coaster moving in a circular path.
At the bottom of the loop, the roller coaster experiences a combination of gravitational and centrifugal forces. The gravitational force pulls the car downward, while the centrifugal force pushes it outward. The apparent weight of the riders is reduced, and at the precise moment when the centrifugal force matches the gravitational force, the normal force becomes zero. This creates a momentary sensation of weightlessness for the riders as the gravitational force is momentarily overcome.
In summary, the normal force on the roller coaster's wheels is zero at the bottom of the loop due to the balance between gravitational and centrifugal forces. This dynamic interaction showcases the principles of circular motion and the interplay between forces acting on the roller coaster.
Therefore, the correct answer is c) Zero.