Braking distances

• What is the main principle behind how brakes work?

  Friction transfers energy from wheels to brakes
• What happens when the brake pedal is pushed?

  Brake pads press onto the wheels, causing friction
• What does the work done between the brakes and wheels transfer?

  Energy from kinetic to thermal energy stores
• How does vehicle speed affect the braking force needed?

  Higher speed requires more work to stop
• What is the consequence of a larger braking force?

  It results in larger deceleration
• Why can very large decelerations be dangerous?

  They may cause brakes to overheat
• How can you estimate the braking force required to stop a vehicle?

  1. Assume uniform deceleration
  2. Use $v^2 =$$u^2 +$$2as$ to find deceleration
  3. Use $F =$$ma$ with known mass
• What is the estimated braking force needed to stop the car?

  12,500 N
• What should you memorize for calculations involving vehicles?

  • Typical speed values
  • Typical mass values
• What should you do if you don't know a vehicle's typical speed or mass?

  Use similar known typical values as a guide
• How does a car's typical mass compare to a bus's typical mass?

  A car has a greater typical mass
• What is a typical speed of a bus?

  25 m/s
• Why is it important to use typical values in calculations?

  To ensure calculations make sense