# G481 Mechanics Definitions

### Description

A complete list of definitions for OCR AS Physics A - G481 Mechanics.
Flashcards by nikeishabk, updated more than 1 year ago
 Created by nikeishabk almost 10 years ago
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## Resource summary

 Question Answer Scalar A quantity that has Magnitude only without direction Examples: Length, area, volume, distance, speed, mass, density, pressure, temperature, energy, work, power, electrical potential, charge, time. Vector A quantity that has (both) magnitude / size and direction Examples: Displacement, velocity, acceleration, momentum, force (lift, drag, thrust, weight), field(s), a.c. voltage, current (when calculating fields only). Displacement (Net) distance moved in a particular direction. Instantaneous speed Speed measured between two point a very small time apart. Average speed Distance covered / time taken. Velocity Speed in a given direction - the rate of change of distance. Acceleration The rate of change of velocity/The gradient of a velocity vs time graph. (= change in velocity / time taken). The Newton The (net) force which gives a mass of 1kg an acceleration of 1 ms-2. Torque of a Couple One of forces × perpendicular distance (between forces) (Not force x perpendicular distance). Moment of a force Moment = force x perpendicular distance from pivot / axis / point. Thinking Distance The distance travelled (by the car) from when the driver sees a problem and the brakes are applied. Braking Distance The distance travelled (by the car) whilst the brakes are applied and the car stops (wtte). Stopping Distance Stopping distance: Thinking distance + braking distance. Work done by a Force Work done = force x distance moved / travelled in the direction of the force. Joule Energy required to move a weight of 1N (through) a distance of 1 m. Power - rate of work done Power = work (done)/time or power = energy/time or power = rate of work done. Watt Power required to move 1N through a distance of 1m in 1 sec (Rate of doing work). Stress Force/(cross-sectional) area. Strain Extension/original length. Young's Modulus Stress/strain. Young modulus is equal to the gradient from stress-strain graph (in the linear region). Ultimate Tensile Strength (UTS) Ultimate tensile strength = Maximum stress material can withstand (before fracture). Elastic Deformation Extension (or compression) force (as long as elastic limit is not exceeded). Plastic Deformation Material does not return to original length / shape/ size (is permanently deformed / longer) when the force / stress is removed. Density Mass/volume or mass per (unit) volume.

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