Stopping Distance

• Stopping distance = thinking distance + breaking distance
• Thinking distance is affected by:

  • Speed
  • Reaction time
• Breaking distance is affected by:

  • Your speed
  • The weather
  • The tyre condition
  • How good the brakes are
• Breaking relies on friction between the brakes and the wheels

  • When the brake pedal is pushed, it causes the brake pads to be pressed onto the wheels
  • This contact force causes friction, which causes work to be done
  • This work causes energy to be transferred from the kinetic store to the thermal energy stores of the brakes
  • This means brakes increase in temperature
• Average reaction time is between 0.2 and 0.9 seconds
• Momentum is how much speed an object has
• The greater the mass or velocity of an object, the higher its momentum. It is a vector quantity
• The force causing a change a change is equal to the rate of change of momentum. A larger force means there is a faster change of momentum
• Car safety features:

  • Crumple zones
  • Seatbelts stretch slightly
  • Airbags inflate

  They all reduce the time it takes for the motion to reach zero