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| Questão | Responda |
| What do we mean by 'work' in science? | Work is done on an object when a force makes the object move. |
| What is the relationship between work and energy? | Energy transferred=work done |
| How do we calculate the work done by force? | Work done(joules)=force(newtons)*distance moved in the direction of the force(metres) |
| What happens to work done to overcome friction? | Work done to overcome friction is transferred as energy that heats the objects that rub together and the surroundings. |
| What does the gravitational potential energy of an object depend on? | The gravitational potential energy of an object depend on its weight and how fat it move vertically. |
| How can we calculate the change of gravitational potential energy of an object when it moves up or down? | The gravitational potential energy of an object increases when the object goes up and decreases when the object goes down. |
| What does the kinetic energy of an object depend on? | On its mass and speed. |
| How can we calculate kinetic energy? | Kinetic energy(J)=0.5*mass(kg)*speed squared(metres per second squared) |
| What is elastic potential energy? | Is the energy stored in an elastic object when work is done on the object. |
| How can we calculate momentum? | Momentum=mass*velocity |
| What is the unit of momentum? | kg m/s |
| Why does momentum have a direction as well as a size? | Momentum is mass*velocity and velocity is speed in a certain direction. |
| When two objects push each other apart do they move away at different speeds? | If they have unequal masses. |
| When two objects push each other apart why is their momentum zero? | Equal and opposite momentum so their total momentum is zero. |
| When vehicles collide, what does the force of impact depend on? | The force of the impact depends on mass, change of velocity, and the duration of the impact. |
| How does the impact force depend on the impact time? | The longer the impact time is, the more the impact force is reduced. |
| What can we say about the impact forces and the total momentum when two vehicles collide? | When two vehicles collide: they exert equal and opposite forces on each other and their total momentum is unchanged. |
| Why do seat belts and air bags reduce the force on people in car accidents? | Seat belts and air bags spread the force across the chest and they can also increase impact time. |
| How do side impact bars and crumple zones work? | Impact bars and crumple zones 'gives way' in an impact so increasing the impact time. |
| How can we work out if a car in a crash was 'speeding'? | We can use the conservation of momentum to find the speed of a car before an impact. |
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