# IB Physics definitions

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- Created by: emmadalton1
- Created on: 08-04-15 13:21

Instantaneous speed

The speed of an object at a particular instant in time.

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Average speed

The distance travelled divided by the time taken.

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Weight

The force on an object due to gravity.

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Newton's 1st Law of Motion

An object with no resultant force acting on it, will travel at a constant speed in a straight line (or remain at rest)

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Newton's second law

F = change in momentum/time (unbalanced force is given by rate of change of momentum)

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Newton's third law

For every force there is an equal and opposite force

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Translational equilibrium

The resultant force acting on the object = 0

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The law of conservation of momentum

The total momentum in any direction, of an isolated system will remain constant

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The law of conservation of total energy

For an isolated system the total energy of the system is a constant value

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Power

The work done in 1 second

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Elastic collision

A collision where the total kinetic energy is conserved

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Frequency

The number of waves per second

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Period

The time taken for one complete wave cycle

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Wavefront

A line of constant phase.

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Damping

The decay of vibrational energy as a result of a force acting in opposition to the motion of the particles

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Intensity

Energy per unit area per unit time

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Refractive index

The speed of light in a vacuum/speed of light in object

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Standing waves

Waves that do not transmit energy

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Progressive wave

Waves that do transmit energy

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Constructive interference

Waves that have a phase difference of 0 degrees. The interference produces that maximum possible displacement.

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Destructive interference

Waves that have a phase difference of 180 degrees. The interference produces the minimum possible displacement

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The Principle of Superposition

Waves of the same type, in the same space at the same time overlap, the displacement is the sum of the displacement of each wave

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Electrical potential difference

The change in the electric potential energy per unit charge when moving a test charge from one point to another.

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The electron volt

The energy gained of lost by an electron when it moves through a voltage of 1V.

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Resistance

The opposition to a flow of current.

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Electromotive force

The energy per unit charge converted into other form from a battery of power supply.

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Gravitational field strength

The gravitational force per unit mass/ the gravitational flux per unit area

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Electric field strength

The electric force per unit charge/the electric flux per unit area

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Magnitude of a magnetic field

The magnetic flux per unit area.

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Unified atomic mass unit

1/12 of the mass of a C-12 atom

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Mass defect

The amount that the total mass of the nucleus is less than the total mass of the nucleus's constituent particles

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Binding energy

The energy required in splitting up the nucleons from the nucleus of an atom

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Energy density of a fuel

The energy stored in a fuel per unit volume

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Albedo

The ratio of light reflected by a planet to the light received by it

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Coefficient of volume expansion

The fractional change in volume as a result of a temperature change of 1K

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Electric potential

The energy per unit charge in moving a test charge from infinity to a given point

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Electric potential energy

The energy needed to move a charge from one point to another

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Gravitational potential

The energy to bring a unit point mass from infinity to a given point

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Gravitational potential energy

The energy needs to bring a point mass from one point to another

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Magnetic flux

A measure of the magnetic fields strength - the total number of magnetic lines of force passing through a specified area in a magnetic field.

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Magnetic flux linkage

Magnetic flux * The number of turns for a coil

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Radioactive decay constant

The probability of a decay of a nucleus per unit time

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Capacitance

The stored charge per unit volt

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Quantum efficiency

The ratio of the number of photoelectrons emitted to the number of photons incident of the pixel

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Magnification

The ratio of the length of the image on the CCD to the actual length of the object

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CCD

A charged couple device (each pixel is converted to an electric charge the intensity of which is related to a colour in the colour spectrum)

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Light year

The DISTANCE traveled by light in one year. (9.4605284 × 10^15 metres)

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Luminosity

The total energy per second given out by an object

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Parsec

The distance an object would be if it had a HELIOCENTRIC PARALLAX of 1 second or an arc

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Absolute magnitude

The magnitude of a star as seen from a distance of 1 parsec

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Critical density

The density of the universe which would halt its expansion at infinite time.

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Principle axis

A line that passes through the centre of curvature of a lens so that light is neither reflected nor refracted

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Focal lens (of a convex lens)

The distance over which the lens will focus plane waves

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Linear magnification (of a convex lens)

The ratio of the image size to the object size

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Power (of a convex lens)

The curvature a lens adds to plane waves. Given by one over the focal length.

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The Dioptre

Unit for measuring curvature by: 1/distance from source of waves

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Far point

The largest distance for which a relaxed eye can focus light onto the retina. For normal vision this is taken as infinity.

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Near point

The closest point an object can be to the eye and still be focuses without strain. For normal vision this is taken at about 25cm

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Angular momentum

The product of the momentum of an object and the perpendicular distance from the axis of rotation.

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## Other cards in this set

### Card 2

#### Front

The distance travelled divided by the time taken.

#### Back

Average speed

### Card 3

#### Front

The force on an object due to gravity.

#### Back

### Card 4

#### Front

An object with no resultant force acting on it, will travel at a constant speed in a straight line (or remain at rest)

#### Back

### Card 5

#### Front

F = change in momentum/time (unbalanced force is given by rate of change of momentum)

#### Back

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