Physics Definitions

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Velocity

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Physics

12th

171 Terms

1

Velocity

rate of change of displacement

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2

Acceleration -

rate of change of velocity

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3

Newton's First Law -

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

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4

Newton's Second Law -

Force equals mass times acceleration

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5

Newton's Third Law -

Every action has an equal and opposite reaction

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6

Elastic collision -

momentum and kinetic energy are conserved

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7

Inellastic collision -

a collision in which only momentum is conserved

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8

Centre of gravity -

The point where the entire weight of an object appears to act.

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9

Torque of a couple -

The force multiplied by the perpendicular distance between the forces

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10

principle of moments -

The sum of the clockwise moments is equal to the sum of the anticlockwise moments of a body in equilibrium.

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11

capacitance -

the amount of charge stored per unit of P.D

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12

electrical potential -

work done moving unit positive charge from infinity to the point

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13

electrical field strength -

Force per unit positive charge

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14

Doppler effect -

An observed change in the frequency of a wave when the source or observer is moving

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15

spontaneous decay -

Decay is not affected by environmental factors

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16

Random Decay -

cannot tell which nucleus will decay next; cannot state at what time a nucleus will decay;

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17

Diffraction of a wave -

When a wave incident to a slit bends

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18

Electric field -

a region of space where a charge will experience a force

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19

Isotope -

Atoms of the same element that have different numbers of neutrons

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20

Luminosity -

The total power emitted by a star.

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21

luminous flux -

the rate at which light is emitted from a source

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22

Hubble's Law -

The observation that the farther away a galaxy is, the faster it is moving away.

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23

Momentum -

The product of an object's mass and velocity

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24

principle of moments -

The sum of the clockwise moments is equal to the sum of the anticlockwise moments.

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25

angular displacement -

the angle turned through in circular motion

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26

angular velocity -

rate of change of angular displacement

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27

centripetal acceleration -

the acceleration of an object moving in a circle, directed toward the centre

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28

centripetal force -

the resultant force towards the centre of a circle acting on an object moving in a circular path

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29

Accuracy -

A description of how close a measurement is to the true value of the quantity measured.

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30

Precision -

a measure of how close a series of measurements are to one another

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31

conservation of momentum -

Momentum of a system remains constant when there are no net external forces acting on it.

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32

terminal velocity -

the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity

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33

centre of gravity -

The point where the entire weight of an object appears to act.

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34

centre of mass -

The point through which a single force on the body has no turning effect

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35

couple -

Two equal and opposite parallel forces that act on an object through different lines of action. It has the effect of causing a rotation without translation.

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36

conservation of energy -

Energy cannot be created or destroyed only transferred from one form to another

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37

efficiency -

The percentage of the input work that is converted to output work

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38

gravitational potential energy -

Energy stored by objects due to their position above Earth's surface.

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39

kinetic energy -

the energy an object has due to its motion

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40

Power -

the rate at which work is done

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41

work done -

force x distance

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42

Compressive deformation -

A change in the shape of an object due to compressive forces

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43

elastic deformation -

region where the material will return to its original shape when the stress is removed

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44

plastic deformation -

permanent deformation caused by strain when stress exceeds a certain value

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45

elastic limit -

Maximum stress that a material will withstand without permanent deformation.

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46

elastic potential energy -

the potential energy of an object that is stretched or compressed

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47

Hooke's Law -

Extension is directly proportional to force until the spring reaches it's elastic limit

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48

Limit of proportionality -

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

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49

spring constant -

a constant that represents the relationship between the force exerted by a spring and its change in length. Higher spring constantx

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50

strain -

ratio of an objects extension to its original length

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51

stress -

force acting per unit area

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52

tensile strength -

the resistance of a material to breaking under tension

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53

Tensile strain -

The extension per unit length

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54

tensile stress -

The force per unit cross-sectional area, measured in Pa

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55

Young's Modulus -

A measure of the stiffness of an elastic material and defined by stress/strain.

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56

Amplitude -

the height of a wave from the origin to the crest

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57

electromagnetic spectrum -

Gamma, X-ray, UV, Visible, Infrared, Micro, Radio

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58

Intensity -

The amount of energy per second carried through a unit area by a wave.

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59

Phase Difference (SHM) - .

Difference in position in cycle of two points expressed as an angle

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60

longitudinal wave -

A wave in which the vibration of the medium is parallel to the direction the wave travels

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61

Transverse wave -

A wave that moves the medium in a direction perpendicular to the direction in which the wave travels

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62

Polarisation -

The restriction of a wave so that it can only oscillate in a single plane. This can only occur for transverse waves.

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63

Progressive wave -

A wave that transfers energy without transferring matter

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64

Antinode -

A point of maximum amplitude on a standing wave

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65

coherence -

Waves with the same frequency and constant phase difference.

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66

constructive interference -

The interference that occurs when two waves combine to make a wave with a larger amplitude

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67

destructive interference -

The interference that occurs when two waves combine to make a wave with a smaller amplitude

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68

Diffraction -

Occurs when an object causes a wave to change direction and bend around it

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69

diffraction grating -

a device made of thousands of closely spaced slits through which light is passed in order to produce a spectrum

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70

interference -

Superposition of two progressive waves from coherent sources to produce a resultant wave with a displacement equal to the sum of the individual displacements from the two waves

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71

Nodes -

The point of minimum displacement in a stationary wave

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72

superposition principle -

when two or more waves overlap, the resulting wave is the sum of the individual waves

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73

Two source interference -

When the waves from two sources interfere to produce a pattern

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74

charge -

the property of a particle that causes it to experience a force in an electromagnetic field

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75

current -

The rate of flow of charge

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76

Light dependent resistor -

Resistor which is designed to have a resistance that changes with light intensity

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77

Ohmic conductor -

A conductor for which the current flow is directly proportional to the potential difference across it, when under constant physical conditions.

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78

potential difference -

the difference in electrical charge between two points in a circuit expressed in volts

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79

Power (circuit) -

rate of energy transfer

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80

resistance -

a measure of how difficult it is for current to flow through a material

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81

Resistivity -

a measure of the resisting power of a specified material to the flow of an electric current.

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82

thermistor - A resistor that changes its resistance with a change of temperature.

A resistor that changes its resistance with a change of temperature.

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83

Volt -

unit of potential difference

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84

conservation of charge -

the principle that net electric charge is neither created nor destroyed but is transferable from one material to another

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85

electromotive force (emf) -

The energy supplied by a source per unit charge passing through the source, measured in volts.

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86

Internal resistance -

resistance inside the source of electrical energy - loss of PD per unit current in the source when current passes through it

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87

Kirchoff's first law (current) -

The sum of the currents entering any junction is always equal to the sum of the currents leaving the junction (a form of conservation of charge).

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88

Kirchoff's Second Law -

The sum of the e.m.f.s is equal to the sum of the p.d.s in a closed loop (a form of conservation of energy).

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89

potential divider -

two or more resistors in series connected to a source of pd

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90

Alpha Particle -

2 protons 2 newtrons highly ionising lowly penetrating

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91

atomic mass unit (amu) -

one twelfth the mass of a carbon-12 atom

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92

Beta particle -

A fast-moving electron that is given off as nuclear radiation. medium ionising, medium penetrating

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93

Beta minus decay -

The process of a neutron inside a nucleus turning into a proton, and emitting a beta-minus particle (an electron) and a antineutrino.

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94

Beta plus decay -

The process of a proton inside a nucleus turning into a neutron, and emitting a beta-plus particle (a positron) and a neutrino.

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95

Electron -

a negatively charged subatomic particle

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96

Hadrons -

Particles that are affected by strong nuclear force, and contain quarks

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97

Leptons -

A group of elementary subatomic particles, consisting of electrons, muons and neutrinos.

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98

Meson -

A hadron consisting of a quark and an antiquark

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99

Positron -

a particle with the mass of an electron but a positive charge

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100

Quark -

particles of matter that make up protons and neutrons

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