Flashcards in Definitions Deck (96)

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1

## Vector

### A physical quantity with magnitude and direction

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## Scalar

### A physical quantity with magnitude only

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## Moment

### Force times perpendicular distance from the line of action of the force to the point

4

## Principle of moments

### For an object in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments about any point

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## Couple

### A pair of equal and opposite forces acting on a body, but not along the same line

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## Velocity

### Change of displacement per unit time

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## Acceleration

### Change of velocity per unit time

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## Newton's 1st Law

### An object will remain at rest or at a constant velocity unless acted on by an external resultant force

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## Newton's 2nd Law

### The force is proportional to the rate of change of momentum

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## Newton's 3rd Law

### For every action there is an equal and opposite reaction

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## Equilibrium

### State of an object when at rest or moving at constant velocity

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## Density

### Mass per unit volume of the substance

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## Stress

### Force per unit area of cross section in a solid perpendicular to the cross section

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## Strain

### Extension per unit length of a solid when deformed

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## Young's Modulus

### Tensile stress/strain

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## Limit of Proportionality

### The limit beyond which, when a wire or a spring is stretched, its extension is no longer proportional to the force that stretches it

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## Plastic deformation

### Deformation of a solid beyond its elastic limit, the object will not return to its original length once the force is removed.

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## Elastic limit

### Point beyond which a wire is permanently stretched

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## Hooke's Law

### The extension of a spring is directily proportional to the force applied to it, up to the limit of proportionality

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## Isotope

### Atoms with the same number of protons but different numbers of neutrons

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## Conservation of energy

### Energy cannot be created or destroyed, only converted from one form to another

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## Work done

### Force times distance moved in the direction of the force

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## Ductile

### Material that can be drwan into threads, it can be shaped or permanently deformed without fracture

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## Brittle

### Material cannot be permanently stretched

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## Wave

### Transfer energy from A to B via a medium of transfer, without transferring the medium

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## Standing wave

### When two waves travel in opposing directions and they have the same wave speed, frequency and in general amplitude, they will superpose and form a standing wave

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## Monochromatic

### Single wavelength

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## Coherent

### No change in phase relationship

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## Diffraction

### Spreading out or bending of waves as they pass through a gap or around an obstacle

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