Decelerations
Physics: AQA GCSE Higher, topic 5.3.23
Work Done when Braking
When we push the brake pedal, brake pads are pressed onto the wheels. This contact causes friction. This causes work to be done. The work done between the brakes and the wheels converts (changes) energy from kinetic energy in the wheels to thermal energy in the brakes. The temperature of the brakes then increases.
Higher speed
- The greater the speed of a vehicle, the greater the braking force needed to stop the vehicle before a certain distance.
- This means that more work needs to be done on the brakes to stop the car.
Higher mass
- The greater the mass of the vehicle, the greater the braking force needed to stop the vehicle. This means that more work needs to be done on the brakes to stop the car.
Higher grip
- For the same work done, the stopping distance will decrease if the force (grip) between the road and the vehicle increases.
Estimating forces
- When a car comes to a stop, the work done by the brakes must equal the initial kinetic energy of the car.
- Work done = initial kinetic energy.
- F d = 1⁄2 m v2.
- We can use this equation to estimate the force applied by the brakes.
Test yourself on Decelerations
Work Done when Braking
Which of these factors increases the work which needs to be done by the brakes to stop the car?
Which of these means less work needs to be done by the brakes to stop the car?