A car parked on a hill. The driver starts the car, accelerates until the car is driving at constant speed, drives at constant speed, then brakes to put the brake pad in contact with the spinning wheels. How is static friction, sliding friction, rolling friction, and air resistance seen in this example?
In this example, different types of friction are involved. Let's break it down and observe how each type of friction is present:
1. Static Friction: When the car is parked on a hill, static friction comes into play. It prevents the car from moving down the hill due to the force of gravity. The static friction opposes the force pulling the car downhill, keeping it stationary.
2. Rolling Friction: Once the driver starts the car and accelerates until it reaches a constant speed, the rolling friction is at work. Rolling friction occurs when two objects roll against each other. In this case, the tires of the car are in contact with the road. The rolling friction helps the car maintain a constant speed while it's in motion.
3. Sliding Friction: When the driver applies the brakes, the brake pads come in contact with the spinning wheels. This action generates sliding friction. Sliding friction opposes the motion of the wheels, which ultimately slows down the car.
4. Air Resistance: Throughout the entire scenario, the car experiences air resistance. Air resistance is a type of friction that objects experience when moving through the air. As the car moves forward, the air molecules interact with its body, creating resistance that opposes its motion. This resistance increases with the car's speed, making it more difficult to maintain constant speed or accelerate.
In summary, the car parked on a hill initially experiences static friction to prevent it from rolling down. Once in motion, rolling friction helps maintain constant speed. When the brakes are applied, sliding friction slows down the car. Additionally, air resistance acts as a force opposing the car's motion throughout the process.