# A2 Physics Definitions

• Created by: Laura
• Created on: 04-03-15 14:26
Newton's 1st Law
A body will continue to remain at rest or continue to move with constant velocity unless acted upon by a force
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Newton's 2nd Law
Force is proportional to the rate of change of momentum
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Newton's 3rd Law
When one body exerts a force on another body, the other body exerts a force that is equal in magnitude and opposite in direction on the first body
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Impulse
Force x time which force acts
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Elastic Collision
Collision in which kinetic energy is conserved
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Inelastic Collision
Collision in which kinetic energy is not conserved, some is lost to the surroundings as heat
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Gravitational Field Strength
Force per unit mass at a point in a gravitational field
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Angular frequency
Product of 2pi x frequency
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Simple Harmonic Motion (SHM)
Acceleration is proportional to displacement from the equilibrium position, and acceleration is always towards the equilibrium position
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Internal Energy
Total of randomly distributed kinetic energy and potential energy of molecules
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Boyle's Law
Pressure is inversely proportional to volume for a fixed mass of gas at a constant temperature
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Latent Heat of Fusion
Thermal energy required to change a solid into a liquid at a constant temperature
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Latent Heat of Vaporisation
Thermal energy required to change a liquid into a gas at a constant temperature
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Electric Field Strength
Force per unit charge
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Magnetic Flux Density
Amount of magnetic flux per unit area
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Tesla
Magnetic flux density is 1 tesla when a wire carrying a current of 1A placed at right angles to the magnetic field experiences a force of 1N per metre of its length
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Weber
Equal to one tesla metre squared
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Product of magnetic flux and number of turns on the coil
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Lenz's Law
Any induced emf will be established to in a direction so as to produce effects which oppose that change that is producing it
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Induced emf is proportional to the rate of change of magnetic flux linkage
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Capacitance
Charge per unit potential difference
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Coulomb per volt
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Time Constant
Time taken for the p.d., charge stored or current to fall to 1/e of its initial value. Calculated by CxR
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Nuclide
A specific combination of protons and neutrons in a nucleus
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Activity
The rate at which radioactive nuclei decay
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Decay Constant
Probability of decay of a nucleus per unit time
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Half Life
Time taken for the activity of a radioactive substance to fall by half
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Binding Energy
The minimum energy needed to separate all of the nucleons in a nucleus
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Binding energy per nucleon
The minimum energy needed to separate all of the nucleons in a nucleus divided by the total number of nucleons
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Parsec
The distance an object must be from the earth to give a parallax angle of 1 arc per second
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Light year
The distance traveled by light through a vacuum in one year
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For a universe infinite in size, static, and with uniformly distributed matter, the night sky should be bright because of light received in all directions from stars.
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Hubble's Law
The speed of recession of a galaxy is proportional to its distance from earth
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Cosmological Principle
The distribution of matter in the universe is homogeneous (evenly distributed) and isotropic (same in all directions) when viewed on a large enough scale
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H(0)
About 2.3 x 10^-18 s^-1. Ratio of the speed of a receding galaxy to its distance from the earth
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Critical Density
The average density the universe would need to be in order for the fate of the universe to be flat. Value = 9.5 x 10^-27 kg/m^3
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Beta Plus Decay
A positron emitted from a nucleus that has undergone nuclear decay
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Beta Minus Decay
An electron emitted from a nucleus that has undergone nuclear decay
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## Other cards in this set

### Card 2

#### Front

Force is proportional to the rate of change of momentum

Newton's 2nd Law

### Card 3

#### Front

When one body exerts a force on another body, the other body exerts a force that is equal in magnitude and opposite in direction on the first body

### Card 4

#### Front

Force x time which force acts

### Card 5

#### Front

Collision in which kinetic energy is conserved