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Definitions Flashcards

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1
Q
A
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2
Q

What is a scalar?

A

A quantity that has magnitude only.

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3
Q

What is a vector?

A

A quantity that has magnitude and direction.

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4
Q

Define the moment (or torque) of a force.

A

The turning effect of a force about a point, defined as the force x the perpendicular distance from the point to the line of action of the force.

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5
Q

What is the principle of moments?

A

For a system to be in equilibrium, the sum of anticlockwise moments about a point equals the sum of clockwise moments about the same point.

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6
Q

What is the centre of gravity?

A

The single point within a body at which the entire weight of the body is considered to act.

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7
Q

Define displacement.

A

The shortest distance from point A to point B, together with the direction.

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8
Q

What is the formula for average speed?

A

Total distance travelled divided by total time taken.

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9
Q

Define instantaneous speed.

A

The rate of change of distance.

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10
Q

What is average velocity?

A

Total displacement divided by total time taken.

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11
Q

Define velocity.

A

The rate of change of displacement.

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12
Q

What is the formula for average acceleration?

A

Change in velocity divided by time taken.

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13
Q

Define acceleration.

A

The rate of change of velocity.

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14
Q

What is momentum?

A

The mass of an object multiplied by its velocity (p = mv).

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15
Q

What does mass measure?

A

The amount of substance (matter) in an object.

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16
Q

Define gravitational field strength (g).

A

The force experienced per unit mass by a mass placed in the field.

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17
Q

What is weight?

A

The force that acts upon an object due to its position in a gravitational field.

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18
Q

What is a resultant force?

A

When the forces acting on an object are unbalanced.

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19
Q

State Newton’s First Law of Motion.

A

An object continues in a state of uniform motion in a straight line or remains at rest unless acted upon by a resultant force.

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20
Q

State Newton’s Second Law of Motion.

A

The rate of change of momentum of an object is proportional to the resultant force acting on it, and takes place in the direction of that force.

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21
Q

State Newton’s Third Law of Motion.

A

If object A exerts a force on object B, then B must exert a force equal in magnitude but opposite in direction on A.

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22
Q

What is an elastic collision?

A

A collision in which there is no loss of kinetic energy.

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23
Q

What is an inelastic collision?

A

A collision in which kinetic energy is lost.

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24
Q

State Hooke’s Law.

A

The extension of an object such as a wire or spring is proportional to the stretching force, provided the extension is not too large.

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25
What is friction?
A force that acts between two surfaces that resists motion between the surfaces.
26
Define terminal velocity.
The constant maximum velocity of an object when the resistive forces on it are equal and opposite to the accelerating forces.
27
What is the formula for extension?
Stretched length minus original length.
28
What is the spring constant (k)?
The force per unit extension.
29
What is efficiency?
Useful output work or energy divided by input work or energy.
30
Define alternating current.
An electric current that periodically reverses in direction in the circuit.
31
What is electric current (I)?
The rate of flow of electric charge.
32
Define potential difference (p.d.), V.
The energy converted from electrical potential energy to some other form per coulomb of charge flowing from one point to the other.
33
What does Ohm's Law state?
The current flowing through a metal wire at constant temperature is proportional to the p.d. across it.
34
Define electrical resistance (R).
The p.d. across a conductor divided by the resulting current through it.
35
What is the angle of incidence?
The angle between an incident ray and the normal to the surface.
36
What is the angle of refraction?
The angle between a refracted ray and the normal to the surface.
37
Define normal.
The line that is perpendicular to a surface.
38
State the Law of Reflection.
The angle of incidence equals the angle of reflection.
39
What is the critical angle?
The angle of incidence which gives an angle of refraction at 90 degrees to the normal of the surface.
40
Define the period (T) for an oscillating body.
The time taken for one complete cycle.
41
What is amplitude (A)?
The maximum displacement of any particle (or wave) from its equilibrium position.
42
Define wavelength.
The minimum distance between two points on the wave oscillating in phase.
43
What is frequency?
The number of cycles of a wave per unit time (second).
44
What is the speed of a wave?
The distance that the wave profile moves per unit time.
45
Define intensity of a wave.
Energy per second passing normally through a given area.
46
What is a transverse wave?
A wave where the particle oscillations are at 90° (right angles) to the direction of travel.
47
What is a longitudinal wave?
A wave where the particle oscillations are in line with (parallel to) the direction of travel.
48
What does Snell's law state?
At the boundary between any two materials, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant.
49
Define refraction.
The change in direction of a wave due to a change in wave speed as it passes across a boundary between two different media.
50
What is refractive index?
The ratio between the speed of light in a vacuum to the speed of light in the medium.
51
What is energy?
The amount of work a body or system can do.
52
What is kinetic energy?
The energy possessed by a body due to its motion.
53
Define potential energy.
The energy stored within an object due to its position, state, or shape.
54
How is work defined?
The product of the magnitude of the force and the distance moved in the direction of the force.
55
What is power?
The work done per second, or energy converted or transferred per second.
56
What is gravitational potential energy?
Energy possessed by virtue of position, calculated as Gravitational PE = mgh.
57
State the Law of Conservation of energy.
Energy cannot be created or destroyed, only transformed from one form to another.
58
Define conduction.
The process by which thermal energy is transmitted through materials from one vibrating particle to another.
59
Define convection.
The process by which thermal energy is transmitted from one place to another by the movement of convection currents due to differences in density.
60
What is radiation?
The transfer of energy by electromagnetic waves.
61
Define density.
The mass per unit volume of an object.
62
What does Boyle's law state?
For a fixed mass of gas at constant temperature, the pressure varies inversely as the volume (p = k/V).
63
What is an ideal gas?
A gas that strictly obeys the gas laws at all pressures, temperatures, and volumes.
64
Define specific heat capacity, c.
The heat energy required, per kilogram, per degree Celsius or Kelvin, to raise the temperature of a substance.
65
What are magnetic field lines?
Lines showing the strength of a magnetic field, from north to south.
66
What differentiates hard and soft magnetic materials?
Hard materials are difficult to magnetise and demagnetise; soft materials are easy to magnetise and demagnetise.
67
What is the motor effect?
A current flowing perpendicular to a magnetic field causing a force.
68
What is induction in electromagnetism?
When a conductor is subjected to a changing magnetic field, a potential difference is created across its ends.
69
Define nucleons.
Protons and neutrons, which reside within the nucleus.
70
What is the atomic mass number, A?
The number of nucleons (protons + neutrons) in an atom's nucleus.
71
What does the atomic number, Z, represent?
The number of protons in an atom's nucleus, determining the chemical element.
72
Define isotopes.
Atoms with the same number of protons but different numbers of neutrons.
73
What is a radioisotope?
Isotopes that are radioactive.
74
What is alpha (α) radiation?
A stream of helium nuclei.
75
What is beta (β) radiation?
A stream of electrons.
76
Define gamma (γ) radiation.
Short wavelength electromagnetic radiation (shorter than X-rays).
77
What is half-life?
The average time taken for the number of radioactive nuclei to reduce to one half of the initial value.
78
What is activity, A, in radioactive decay?
The rate of decay (number of disintegrations per second) of a sample.
79
Define nuclear fission.
The process in which a large nucleus is split to release energy.
80
What is nuclear fusion?
The process in which two small nuclei are joined together to release energy.
81
What is the universe?
A large collection of billions of galaxies.
82
Define a galaxy.
A large collection of billions of stars.
83
What is redshift?
The increase in the wavelength of received light from distant galaxies supporting an expanding universe.
84
What is the Doppler Effect?
The change in the apparent frequency of a wave due to relative motion between the source and the observer.
85
What is cosmic microwave background radiation (CMB)?
Microwave radiation detected from all directions, theorized to be leftover from the Big Bang.
86
POWER is the ____ of energy transfer
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PHYICS (10 decks)

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