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| Question | Answer |
| Explaining Motion P4 | -Speed and velocity -S-T and D-T diagrams -Interaction pairs and forces -Balanced/ unbalanced forces -Momentum -Work -Energy |
| Speed | Speed= distance/ time |
| Velocity | Velocity is speed with direction |
| Instantaneous speed | The speed you are doing in that instant |
| Distance-Time graphs | A DT graph plots the position of an object along a time axis in a journey. The graph can be used to calculate speed at certain points and has features you need to recognise. |
| Displacement | The distance between starting point and object in a particular direction (Not distance journeyed) |
| Acceleration | Acceleration= change in speed/ time taken for change |
| Forces | Forces are everywhere making things move or keeping them in their place. Measured in Newtons, N they push and pull everything. |
| Examples of forces | Gravity Air resistance Magnetic Upthrust Friction Lift |
| Interaction pairs of forces | Objects start moving (or stop) due to forces acting on them. Consider two people on an ice rink. One force acts on one object, one force acts on another. Opposite directions. Forces are equal in size. |
| Gravity | Gravity is another non-contact force and it will also come in interaction pairs, although the force is hard to spot. Gravity is due to Earth's pull on apple. Gravity is due to apple's pull on Earth. |
| Energy | Energy is property of an object, transferable between 9 different types (but can't be created or destroyed) It is measured in Joules, J |
| 9 different types of energy | Sound Chemical Electrical Kinetic Gravitational potential Elastic Nuclear Heat Light |
| An object that is moving has kinetic energy | KE= 1/2 mass X velocity squared |
| An object that has been lifted has gravitational potential energy, a measure of what it could go on to do | GPE= weight X height |
| Work | Work is done whenever a force acts on a moving object. The amount of work is found by multiplying the force with the distance moved in that direction; it is the same as the energy transferred. |
| Momentum | Momentum is another abstract quantity linked to motion. Momentum is always conserved. Momentum= mass X velocity |
| Change in momentum | Forces change the momentum of an object. The bigger the force or the longer it acts for, the greater the momentum change. Change in momentum= force X time |
| Kinetic energy | Kinetic energy may not be conserved. Also, it does not have a direction. |
| Crumple zones | Makes the duration of the collision longer Makes the average force exerted on the car less The longer time it takes to change a passengers speed to zero, the smaller the average force exerted. |
| Seat belts | Makes change of momentum take longer Top part of the body will move forward |
| Air bag | Cushions impact Reduces momentum |
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