Braking and Momentum Flashcards
What is the name given to the distance a vehicle travels to safely come to a stop after the driver has spotted a hazard?
Stopping distance
What is thinking distance?
The distance vehicle travels during driver’s reaction time
What is braking distance?
The distance vehicle travels once brakes have been applied
What is the relationship between stopping distance, thinking distance and braking distance?
Stopping distance = thinking distance + braking distance
Does the speed of a vehicle have a bigger effect on braking distance or thinking distance?
Braking distance
Which distance is proportional to the speed of the vehicle?
Thinking distance
Which distance increases by an increasing amount as speed increases?
Braking distance
What are three factors that can affect the braking distance of a vehicle?
Speed, road conditions, condition of tyres and brakes
What is the definition of one joule of work?
The work done when 1N of force causes 1m displacement
Why does the temperature of the vehicle’s brakes increase when the brakes are applied?
Work done by the frictional force between the brakes and the wheels transfers energy from the kinetic energy store of the car to the thermal energy store of the 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 law of conservation of momentum?
In a closed system, the total momentum before an event is equal to the total momentum after it
What does mΔv stand for?
Change in momentum
How is the force acting on an object related to its momentum?
Force acting on an object = rate of change of momentum
What are examples of everyday safety features which work by increasing the time taken for the change in momentum?
Air bags, seat belts, crumple zones in cars, cycle helmets, crash mats in gyms, cushioned surfaces in children’s playgrounds
