Physics Mechanics Definitions 4.5 / 5 based on 6 ratings ? PhysicsMotionASOCR Created by: Hannah CastreyCreated on: 09-12-12 13:13 Displacement The distance between two points measured in a particular direction. 1 of 29 Speed The rate of change of distance with time. 2 of 29 Instantaneous speed The speed at a particular instant in time. 3 of 29 Velocity The rate of change of displacement with time. 4 of 29 Acceleration Rate of change of velocity with time. 5 of 29 Scalar quantities State only magnitude. 6 of 29 Vector quantities State magnitude and direction 7 of 29 1 Newton Force which gives a mass of 1kg an acceleration of 1ms-2 8 of 29 Equilibrium If the resultant force acting on an object is zero, the object is said to be in equilibrium. 9 of 29 Centre of gravity The centre of gravity of a body is the point at which the whole weight of the body may be considered to act. 10 of 29 Moments The moment of a force is given by the product of the force and the perpendicular distance. 11 of 29 Principle of moments Sum of the clockwise moments about any point provided by the forces acting on the object equals the sum of the anticlockwise moments about that point. 12 of 29 Torque of a couple One of the forces multiplied by the perpendicular distance between them. 13 of 29 Couple Two equal and opposite forces act on an object. The resultant is zero so it wont accelerate but will rotate. 14 of 29 Density Mass per unit volume of a material. 15 of 29 Pressure The force acting per unit area. 16 of 29 Thinking distance The distance travelled between seeing a danger and putting your foot on the brake. 17 of 29 Braking distance The distance travelled between putting your foot on the brake and the vehicle stopping. 18 of 29 Stopping distance Thinking distance multiplied by braking distance. 19 of 29 Motive power Force multiplied by velocity. 20 of 29 Joule One joule is the work done when a force of 1N moves one metre in the direction of the force. 21 of 29 Work done Work is done when a force moves it's point of application along the direction of its line of action. 22 of 29 Power Power is the rate at which work is done or energy is converted. 23 of 29 Watt One watt is the power developed when one joule of work is converted in one second. 24 of 29 Hooke's law The force applied to a spring is directly proportional to the extension produced. 25 of 29 Spring contant .Force needed to produce unit extension. 26 of 29 Stress Force acting per unit cross-sectional area of the material. 27 of 29 Strain The fractional increase in length of the wire. 28 of 29 Young Modulus Stress required to produce unit strain. 29 of 29

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