Braking Distances

• Braking Distances


  How the brakes actually work to slow down a car
• Braking


  1. Brake pedal is pushed

  2. Brake pads are pressed onto the wheels

  3. Friction causes work to be done

  4. Energy is transferred from the kinetic energy stores of the wheels to the thermal energy stores of the brakes

  5. Brakes increase in temperature
• The faster a vehicle is going

  The more energy it has in its kinetic store, so the more work needs to be done to stop it
• A larger braking force


  Means a larger deceleration
• Very large decelerations can be dangerous because they may cause brakes to overheat (so they don't work as well) or could cause the vehicle to skid
• Estimating the braking force required to stop a vehicle

  1. Assume the deceleration is uniform

  2. Rearrange v-u=2as to find the deceleration

  3. Use F=ma, with m=-1000 kg