Work, Energy & Momentum - Chapter 3 Physics Unit 2 Revision 3.0 / 5 based on 1 rating ? PhysicsEnergyGCSEAQA Created by: Lily BrightonCreated on: 31-12-12 14:45 What is the SI unit of work done? Joules (J) 1 of 16 How is work done to overcome friction? It is transferred as energy that heats the objects that rub together and the surroundings. 2 of 16 What is gravitational potential energy? Energy that is stored in an object which is dependent on its position in the Earth's gravitational field. 3 of 16 What is power and what is its equation? Power is the rate of energy transfer and its equation is: Power = Energy / time 4 of 16 What is elastic potential energy? Energy stored in an elastic object when the work is done on the object. 5 of 16 When do objects have kinetic energy and momentum? When they are moving. 6 of 16 When is momentum conserved? Whenever objects interact, providing no external forces act on them. 7 of 16 What happens to objects in an explosion? The objects move apart with equal and opposite momentum. 8 of 16 What is the total momentum after an explosion and why? Zero, becauseone momentum is positive and the other is negative, so the total momentum after the explosion is zero. 9 of 16 When vehicles collide, what does the force of the impact depend on? Mass, change of velocity and the duration of the impact. 10 of 16 What is impact time? Time taken for a collision to take place. 11 of 16 Why do cars have crumple zones at both the front and the rear? Cars may be hit from either the front or the rear, in either case the crumple zone reduces the forces on the car. 12 of 16 What do seat belts and air bags do? They spread the force across the chest and they also increase the impact time.H 13 of 16 What do seat belts and air bags do? They spread the force across the chest and they also increase the impact time.H 14 of 16 How can you find out the speed of the car after a collision? Use the conservation of momentum. 15 of 16 How can you find out the speed of the car after a collision? Use the conservation of momentum. 16 of 16
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