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Motion definitions
AQA A level physics
| Term | Definition |
|---|---|
| Efficiency | The ratio of useful energy transferred by a device to the energy supplied |
| Centre of gravity | The point through which all of a bodies weight acts |
| Acceleration – Equation and definition | a=(v-u)/t, Change in velocity per unit time |
| Displacement | Distance travelled in a given direction |
| Equilibrium | State of an object at rest or in uniform motion |
| Conditions for equilibrium | Resultant force zero & resultant torque zero. |
| Inertia | Resistance of a body to changes in its motion |
| Kinetic energy | Energy of a body due to its motion, 1/2 mv^2 |
| Newton’s first law | An object remains at rest of in uniform motion unless it is acted upon by a force |
| Newton’s second law (constant mass) | Resultant force = mass x acceleration |
| Principle of moments | Object in equilibrium: sum of clockwise moments about any point equals the sum of the anticlockwise moments |
| Terminal speed | Max speed. The resultant force (of drag and weight) is equal to zero |
| Torque of a couple | The total force x perpendicular distance between the line of action of the forces |
| Moment of a force about a point | Force x perpendicular distance between the line of action of the force and the point |
| Work | Force x distance moved in the direction of the force |
| Free fall | The force due to gravity is the only force acting on an object |
| Assumptions for projectiles | Air resistance is said to be negligible and the horizontal velocity is constant |
| Significance of a closed triangle of vectors | Resultant force is zero / Forces in equilibrium |