When a car goes around a curve (without skidding), on a level road,
Select one:
a. no friction force is needed because the car simply follows the road.
b. the friction force of the road on the car increases when the car’s speed decreases.
c. the friction force of the road on the car increases when the car’s speed increases.
d. the friction force of the road on the car increases when the car moves to the outside of the curve.
e. there is no net friction force because the road and the car exert equal and opposite forces on each other.
F = m Ac
= m v^2/R
F increases as speed increases
To determine the correct answer, we need to understand the concept of centripetal force in circular motion. When a car goes around a curve, it experiences centripetal acceleration, which means there must be a centripetal force acting on the car to keep it moving in a curved path.
The centripetal force required comes from the friction force between the car's tires and the road. According to Newton's laws of motion, the friction force acts towards the center of the curve, providing the necessary centripetal force.
Let's evaluate each option:
a. No friction force is needed because the car simply follows the road.
This option is incorrect because without the friction force, the car would not be able to turn on a curved path. Friction is essential to provide the required centripetal force.
b. The friction force of the road on the car increases when the car's speed decreases.
This option is incorrect. The friction force required is determined by the curvature of the curve, not the car's speed. Therefore, the friction force does not increase when the car's speed decreases.
c. The friction force of the road on the car increases when the car's speed increases.
This option is also incorrect. The speed of the car does not affect the friction force required for a given curve. The friction force only depends on the car's mass, its acceleration towards the center of the curve, and the radius of the curve.
d. The friction force of the road on the car increases when the car moves to the outside of the curve.
This option is incorrect. The friction force required to keep the car moving in a curved path remains constant unless the parameters, such as the mass of the car or the curvature of the curve, change.
e. There is no net friction force because the road and the car exert equal and opposite forces on each other.
This option is also incorrect. While it's true that the car exerts a reaction force on the road, the net friction force necessary for circular motion is not zero. The road's friction force acting on the car is the centripetal force required to keep the car moving in a curved path.
Based on the explanations, the correct answer is option c. The friction force of the road on the car increases when the car's speed increases.