Important Definitions Flashcards

1
Q

speed

A

the distance travelled by an object per unit time

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2
Q

velocity

A

the speed of an object in a stated direction

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3
Q

acceleration

A

the rate of change of an object’s velocity

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4
Q

mass

A

is the quantity of matter a body is composed of; mass causes the object to resist changes in its motion and causes it to have a gravitational attraction for other objects

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5
Q

weight

A

the downward force of gravity that acts on an object because of its mass

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6
Q

gravitational field strength

A

the gravitational force exerted per unit mass placed at a point

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7
Q

density

A

the ratio of mass to volume for a substance

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8
Q

spring constant

A

is the constant of proportionality in Hooke’s law and is a measure of the stiffness of a spring

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9
Q

solid friction

A

the resistance to motion caused when two surfaces are in contact

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10
Q

moment

A

the turning effect of a force about a pivot; given by f x perpendicular d from the pivot

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11
Q

centre of gravity

A

all the mass of an object could be located here (force of gravity acts on the mass) and the object would behave the same (when ignoring any spin)

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12
Q

momentum

A

the quantity mass x velocity, p=mv

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13
Q

impulse

A

the change in an objects momentum, changeinp, or the force acting on an object multiplied by time for which the force acts (F x t)

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14
Q

resultant force

A

a single force which has the same effect on a body as two or more forces

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15
Q

work done

A

the amount of energy transferred when one body exerts a force on another; energy transferred by a force when it moves; work done= energy transferred

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16
Q

power

A

the rate at which work is done, or the rate at which energy is transferred

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17
Q

efficiency

A

the fraction or percentage of energy supplied that is usefully transferred

18
Q

pressure

A

the force acting per unit area at right angles to a surface

19
Q

transverse wave

A

a wave in which the vibration is at right angles to the propagation of the wave

20
Q

longitudinal wave

A

a wave in which the vibration is forward and back, parallel to the direction of the propagation of the wave

21
Q

refractive index

A

the ratio of the speeds of light wave in two different media

22
Q

Total internal reflection

A

when a ray strikes the inner surface of a material and 100% of the light reflects back inside it

23
Q

Critical angle

A

the minimum angle of incidence at which total internal reflection occurs; incident ray that refracts along the surface of the medium at 90 degrees

24
Q

principal axis

A

the line passing through the centre of a lens perpendicular to its surface

25
Q

principal focus

A

(or focal point) the point at which rays of light parallel to the axis converge after passing through a converging lens

26
Q

monochromatic

A

describes a ray of light (or other electromagnetic radiation) of a single wavelength and single frequency

27
Q

magnetic field

A

a region of space around a magnet or electric current, in which a pole experiences a force

28
Q

direction of magnetic field

A

direction of the force on the N pole at that point

29
Q

electric field

A

a region of space in which an electric charge will experience a force

30
Q

direction of electric field

A

the direction of a force on a positive charge at that point

31
Q

current

A

the rate at which electric charge passes a point in a circuit

32
Q

e.m.f

A

the electrical work done by a source (cell, battery, etc.) in moving a unit charge around a circuit; the voltage across the terminals of a source

33
Q

p.d

A

the work done by a unit charge passing through an electrical component; another name for voltage across two points

34
Q

background radiation

A

the radiation from the environment to which we are exposed all the time

35
Q

nuclear fission

A

the process by which energy is released by the splitting of a large, unstable, heavy nucleus into two or more smaller nuclei

36
Q

nuclear fusion

A

the process by which energy is released when two small light nuclei join together to form a new large, heavier nucleus

37
Q

radioactive decay

A

the emission of alpha, beta, or gamma radiation from an unstable nucleus

38
Q

half-life

A

the average time taken for half the atoms in a sample of radioactive material to decay

39
Q

redshift

A

in increase in the observed wavelength of electromagnetic radiation (including visible light) from a star or galaxy because it is moving away from us

40
Q

cosmic microwave background radiation

A

wavelength of light in the microwave region

41
Q

hubble’s constant

A

ratio of the speed at which the galaxy is moving away from Earth to its distance from Earth (the slope of galaxy speed against distance)

42
Q

ultrasound

A

sound with a frequency higher than 20,000 Hz