# Definitions - Physics

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A physical quantity that has magnitude only
Scalar
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A physical quantity that has both magnitude and direction
Vector
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The single vector which has the same effect as the original vectors acting together
Resultant vector
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The length of path traveled (scalar quantity)
Distance
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A change in position (vector quantity)
Displacement
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The rate of change of distance
Speed
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The rate of change of displacement
Velocity
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The rate of change of velocity
Acceleration
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The force or the component of a force which a surface exerts on an object with which it is in contact, and which is perpendicular to the surface
Normal force
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The force that opposes the motion of an object and acts parallel to the surface
Frictional force
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The force that opposes the tendency of motion of a stationary object relative to an object
Static friction
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The force that opposes the motion of a moving object relative to a surface
Kinetic friction
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A body will remain in its state of rest or motion at constant velocity unless acted upon by a net resultant force
Newton's FIRST Law of Motion
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When a net resultant force acts on an object, the object will accelerate in the direction of the force at an acceleration directly proportional to the force and inversely proportional to the mass of the object
Newton's SECOND Law of Motion
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When one body exerts a force on a second body, the second body exerts a force of equal magnitude in the opposite direction of the first body
Newton's THIRD Law of Motion
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Each body in the universe attracts every body with a force that is directly proportional to the product of their masses and inversely proportional to the squared distance between their centres
Newton's Law of UNIVERSAL GRAVITATION
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The gravitational force that Earth exerts on any object or near its surface
Weight
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The speed of light is constant when travelling through a specific medium
Speed of light
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A change of wave speed in different media, while its frequency remains constant
Refraction
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The ratio of the speed of light in air to the speed of light in a specific medium
Refractive Index
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The imaginary line perpendicular to the surface between two different optical media
Normal
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A measure of the speed of light or other electromagnetic waves through a medium
Optical Density
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The angle between the incident ray and the normal
Angle of Incidence
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The angle between the refracted ray and the normal
Angle of Refraction
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Gives the relationship between the angle of incidence, the angle or refraction and the refractive index when light moves from one medium to another
Snell's Law
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The angle of incidence from which the refractive angle is 90 degrees
Critical angle
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The angle of incidence is greater than the critical angle and no refraction takes place, instead the ray is reflected
Total internal reflection
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An imaginary line that connects waves that are in phase
Wavefront
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All points of a wavefront act like a point source. Each of these point sources produce smaller circular wavelets moving forwards with the same speed as the wave
Huygen's Principle
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The ability of a wave to spread out in wavefronts as they pass through a small aperture or around a sharp edge
Diffraction
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The magnitude of the electrostatic force exerted by one point charge on another point charge is directly proportional to the product of the magnitude of the charges and inversely proportional to the square of their distance between them
Coulomb's Law
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A region of space in which an electric charge experiences a force. The direction of the electric field at a point is the direction that a positive test charge would move if placed at that point
Electric field
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The electric field at a point is the electrostatic force experienced per unit positive charge placed at that point
Electric field at a point
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When a conductor and magnetic field move relative to each other, an EMF is induced across the ends of the conductor. The induced EMF in the conductor is directly proportional to the rate of change of the magnetic flux
Electromagnetism
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The potential difference accross a conductor is directly proportional to the current in the conductor at constant temperature
Ohm's Law
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A conductor that obeys Ohm's Law
Ohmic conductor
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A conductor which does not obey Ohm's Law
Non-ohmic conductor
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Resistance of a cell/battery itself
Internal resistance
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The rate at which electrical energy is converted in an electric circuit and is measured in Watts
Power
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Refers to the use of 1 kilowatt of electricity for 1 hour
Kilowatt hour (kWh)
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## Other cards in this set

### Card 2

Vector

#### Back

A physical quantity that has both magnitude and direction

Resultant vector

Distance

Displacement