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| Question | Answer |
| Whenever two objects interact, the forces they exert on each other are... | Whenever two objects interact, the forces they exert on each other are equal and opposite. |
| What is meant by resultant force? | A number of forces acting at a point may be replaced by a single force that has the same effect on the motion as the original forces all acting together. This single force is called the resultant force. |
| What do resultant forces cause? | A resultant force acting on an object may cause a change in its state of rest or motion. |
| What is the effect of resultant forces on stationary objects | If the resultant force acting on a stationary object is: ■ zero, the object will remain stationary ■ not zero, the object will accelerate in the direction of the resultant force. |
| How is force, mass and acceleration linked? | The acceleration of an object is determined by the resultant force acting on the object and the mass of the object. a=F/m or F=m×a |
| What does the gradient of a distance–time graph represent? | The gradient of a distance–time graph represents speed. |
| How can acceleration be calculated? | The acceleration of an object is given by the equation: a=(v-u)/t |
| What does the gradient of a velocity–time graph represent? | The gradient of a velocity–time graph represents acceleration. |
| How can distance be calculated from a velocity-time graph? | Area under the graph |
| Describe the forces acting when a vehicle travels at a steady speed | When a vehicle travels at a steady speed the resistive forces balance the driving force. |
| What is a car's stopping distance? What parts make it up? | The stopping distance of a vehicle is the sum of the distance the vehicle travels during the driver’s reaction time (thinking distance) and the distance it travels under the braking force (braking distance). |
| What factors can affect a driver's reaction time? | A driver’s reaction time can be affected by tiredness, drugs and alcohol. |
| How do car brakes slow a car? | When the brakes of a vehicle are applied, work done by the friction force between the brakes and the wheel reduces the kinetic energy of the vehicle and the temperature of the brakes increase. |
| What factors can affect a car's braking distance? | A vehicle’s braking distance can be affected by adverse road and weather conditions and poor condition of the vehicle. |
| How does drag change with speed? | The faster an object moves through a fluid the greater the frictional force that acts on it. |
| Describe the motion of a falling object in a fluid | An object falling through a fluid will initially accelerate due to the force of gravity. Eventually the resultant force will be zero and the object will move at its terminal velocity (steady speed). |
| How is weight calculated? | Calculate the weight of an object using the force exerted on it by a gravitational force: W=m×g |
| What can affect the shape of an object? | A force acting on an object may cause a change in shape of the object. |
| What can a force do to an elastic object? | A force applied to an elastic object such as a spring will result in the object stretching and storing elastic potential energy. |
| What is stored in a stretched spring? | For an object that is able to recover its original shape, elastic potential energy is stored in the object when work is done on the object to change its shape. |
| How are force and extension linked in an elastic object? | The extension of an elastic object is directly proportional to the force applied, provided that the limit of proportionality is not exceeded: F=k×e |
| What causes work to be done? | When a force causes an object to move through a distance work is done. |
| Calculate work done | Work done, force and distance are related by the equation: W=F×d |
| What is work done the same as? | Energy is transferred when work is done. |
| What is power? How is it calculated? | Power is the work done or energy transferred in a given time: P=E/t |
| What is gravitational potential energy? How is it calculated? | Gravitational potential energy is the energy that an object has by virtue of its position in a gravitational field. Ep=m×g×h |
| What is kinetic energy? How is it calculated? | The kinetic energy of an object depends on its mass and its speed. Ek=1/2×m×v^2 |
| How is momentum calculated? | Momentum is a property of moving objects. p=m×v |
| What is conservation of momentum? | In a closed system the total momentum before an event is equal to the total momentum after the event. This is called conservation of momentum. |
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