Physics 2.3

• How is work calculated?

  Force X Distance moved
• What must happen when work is done?

  The total energy in the system must stay the same

  The energy started with must equal the energy ended with
• What is work done?

  When a force acts on a moving body, energy is transferred. The energy transferred is work done
• What are the main safety features of cars?

  Seat belts- stop a passenger moving forward in a collision

  Crumple zones- areas of the car which change shape or compresses during a collision

  Air bags- deploy to the front and sides of a passenger in a collision
• How can inertial losses be reduced?

  using lighter materials
• How can idling losses be reduced?

  Start-stop systems to automatically stop and restart the engine
• How can rolling losses be reduced?

  Having correctly inflated tyres

  Including sensors in the tyres to monitor the pressure
• How can aerodynamic losses be reduced?

  By using more streamlined designs: less air resistance acting on the vehicle
• How can vehicles efficiency be improved?

  Reducing aerodynamic losses due to air resistance

  Rolling resistance due to friction between tyres and the road

  Idling losses due to the engine using fuel when the vehicle is stationary

  Inertial losses due to the fuel used when accelerating
• What is gravitational field strength?

  The energy an object possesses due to its position

  change in potential energy= mass X gravitational field strength
• What is kinetic energy?

  The energy an object possesses due to its motion

  kinetic energy = mass X velocity squared divided by 2
• How can you find the work done in stretching a spring?

  By finding the area under the force-extension graph
• What happens to the elastic energy in a spring when the extension increases?

  Increases
• How can spring constant be worked out?

  Force = extension

  or

  Finding the gradient of the straight part of the graph
• If a spring has a spring constant of 30N/m how much force will it need to extend by 1m?

  30N
• What happens when friction occurs on the objects?

  Some energy may be transferred into thermal (heat) energy

  the total energy must remain the same
• When work is done what must remain constant?

  Total amount of energy this is known as conservation of energy
• How can an object possess energy?

  It’s motion (kinetic energy)

  its position (gravitational potential energy)

  deformation (elastic energy)
• How do air bags keep a passenger safe during a collision?


  air bags increase the distance over which the energy is transferred so the force acting on a passenger decreases