P3D-F Revision Resources

P3D-F Revision Resources

1. P3D

   • 1. Work is done when a force moves an object.
   • 2. As work done is a measure of how much energy is transferred, it has the same unit as Energy, joules (J).
   • 3. The force of attraction on a mass due to gravity is called weight.
   • 4. On Earth, g = 10N/kg.
   • 5. When a car brakes the kinetic energy lost = work done by the brakes.
   • 6. Power (watts, W) measures how much work is done in a particular time.
   • 7. More powerful cars require more energy every second and need more fuel.
   • 8. Both the power rating of a car and its engine size are related to fuel consumption.

2. P3E

   • 1. All moving object have Kinetic Energy.
   • 2. Cars can use fossil fuels, biofuels, and solar energy or be battery powered.
   • 3. Batteries need to be recharged; most electricity for this comes from fossil fuelled polluting power stations.
   • 4. Streamlining shapes can reduce friction forces and decrease fuel consumption.
   • 5. Fuel consumption of a vehicle can be affected by: - its speed, its KE, its shape, the driving style of the driver and the road surface.
   • 6. When the mass of a car is doubled, its KE is doubled.
   • 7. When the speed of a car is doubled, its KE & braking distance is quadrupled.

3. P3F

   • 1. A rapid change in momentum (eg in a car crash when mom suddenly becomes zero) means there. is a large force on the occupants.
   • 2. To minimise the forces in a crash the change in mom must take as long as possible. ie longer time, less injuries.
   • 3. Safety features of a modern car include:- brakes, crumple Zones, seatbelts, air bags.
   • 4. These safety features will change shape, absorb energy, reduce injuries, and reduce mom to zero more slowly so reduce the force on the passengers.
   • 5. Safety features are tested using crash test dummies.
   • 6. ABS brakes give a vehicle stability and maintain steering when braking hard or going into a skid. ABS continually pumps the brakes on and off to get maximum braking force without skidding.