Braking and momentum

• What is the name of the distance a vehicle travels from observing hazard to stopping?

  Stopping distance.
• What is thinking distance?

  Distance travelled during driver's reaction time (between seeing hazard and pressing brakes).
• What is braking distance?

  Distance travelled while brakes are applied(from pressing brakes to stopping).
• What is the relationship between stopping distance, thinking distance and braking distance?

  Stopping distance = thinking distance + braking distance.
• In which direction does drag act on an object?

  In opposite direction to movement.
• Name factors that affect thinking distance.

  Speed, tiredness, alcohol, drugs.
• Name factors that affect braking distance.

  Speed, road conditions, conditions of brakes and tyres.
• Does the speed of a vehicle have a bigger effect on thinking or braking distance?

  Braking distance.
• What is the relationship between speed and thinking distance?

  Directly proportional; as speed doubles, thinking distance doubles.
• What is the relationship between speed and braking distance?

  As speed doubles, braking distance quadruples.
• Why does the temperature of a vehicle's brakes increase when the brakes are applied?

  Work done by the frictional force between the brakes and the wheels transfer energy from kinetic energy store of the car to the thermal energy store of brakes.
• What can happen if the braking force used to stop a vehicle is very large?

  Brakes may overheat/car may skid.
• What is the equation for calculating momentum?

  Momentum(kg m/s) = mass(kg) x velocity(m/s)

  $p=$$mv$
• What is the unit for momentum?

  kg m/s
• What is law of conservation of momentum?

  In a closed system:

  momentum before = momentum after.