Physics definitions

Question 1

scalar

Answer 1

quantity with magnitude only

Question 2

vector

Answer 2

quantity with magnitude and direction

Question 3

moment

Answer 3

force * perpendicular distance from pivot

Question 4

displacement

Answer 4

the shortest distance between 2 points

Question 5

terminal velocity

Answer 5

constant maximum velocity of an object when resistive forces balance accelerating forces

Question 6

momentum

Answer 6

mass * velocity

Question 7

N2L

Answer 7

rate of change of momentum of an object is proportional to the resultant force

Question 8

N3L

Answer 8

if body A exerts a force on B, then B exerts and equal and opposite force on A

Question 9

principle of conservation of momentum

Answer 9

the vector sum of moments in a system remains constant provided there is no external force

Question 10

elastic collision

Answer 10

collision where there is no change in the kinetic energy

Question 11

inelastic collision

Answer 11

collision where kinetic energy is lost

Question 12

work

Answer 12

magnitude of the force * distance moved in direction of force

Question 13

principle of conservation of energy

Answer 13

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

Question 14

potential energy

Answer 14

energy possessed by an object due to its position

Question 15

kinetic energy

Answer 15

energy possessed by an object due to its velocity

Question 16

elastic potential energy

Answer 16

energy possessed by an object when it is deformed by forces acting on it

Question 17

energy

Answer 17

the amount to work it can do

Question 18

power

Answer 18

energy transferred per second / work done per second

Question 19

Hooke’s law

Answer 19

the tension in a spring or a wire is proportional to its extension, provided the extension is not too great

Question 20

spring constant

Answer 20

the force per unit extension

Question 21

stress

Answer 21

force per cross-sectional area

Question 22

strain

Answer 22

extension per unit length due to applied stress

Question 23

young modulus

Answer 23

stress / strain

Question 24

ductile material

Answer 24

material that can be drawn into a wire

Question 25

elastic limit

Answer 25

point where deformation ceases to be elastic

Question 26

brittle material

Answer 26

material with no region of plastic flow

Question 27

black body

Answer 27

a body that absorbs all electromagnetic radiation that falls on it and emits all electromagnetic radiation equally

Question 28

Wien's displacement law

Answer 28

the wavelength of peak emission from a black body is inversely proportional to the absolute temperature

Question 29

Stefan's law

Answer 29

P = Aσt^4

Question 30

luminosity of a star

Answer 30

the total energy a star emits per unit time

Question 31

intensity

Answer 31

I = P / 4πR^2

Question 32

lepton

Answer 32

a fundamental particle that does not experience the strong force

Question 33

hadron

Answer 33

particles consisting of quarks and antiquarks that experience the strong force

Question 34

baryon

Answer 34

a hadron made up of 3 quarks or 3 antiquarks

Question 35

meson

Answer 35

a hadron consisting of a quark-antiquark pair

Question 36

electric current

Answer 36

rate of flow of electric charge

Question 37

potential difference

Answer 37

work done per unit charge moved | V = W / Q

Question 38

Ohm's law

Answer 38

the current in a wire is proportional to the pd provided external conditions remain constant

Question 39

electrical resistance

Answer 39

the pd per unit current | R = V / I

Question 40

resistivity

Answer 40

the resistance of a 1m length with 1m^2 cross-sectional area | ρ = RA / l

Question 41

emf

Answer 41

the energy converted from a form into electrical potential energy per coulomb of charge through the source

Question 42

progressive wave

Answer 42

a pattern of disturbances travelling through a medium and carrying energy through it, involving oscillations around their equilibrium positions

Question 43

transverse wave

Answer 43

a wave where the particles oscillate at right angles to the direction of travel

Question 44

longitudinal wave

Answer 44

a wave where the particles oscillate in the direction of travel

Question 45

polarised wave

Answer 45

a transverse wave in which particles only oscillate in one direction

Question 46

in phase

Answer 46

two waves that have the same frequency and are in the the same point in their cycles

Question 47

wavelength

Answer 47

minimum distance between 2 points on the wave oscillating in phase

Question 48

frequency

Answer 48

the number of cycles of a wave that pass a given point in one second

Question 49

speed of a wave

Answer 49

the distance that a wave profile moves in a unit time

Question 50

diffraction

Answer 50

the spreading out of waves when they meet obstacles

Question 51

the principle of superposition

Answer 51

if waves from 2 sources occupy the same region then the total amplitude at any point is the vector sum of the amplitudes at that point

Question 52

phase difference

Answer 52

the difference in position of 2 points within a cycle of oscillation

Question 53

coherence

Answer 53

waves or wave sources which have a constant phase difference between them

Question 54

stationary wave

Answer 54

a pattern of disturbances in a medium in which energy is not propagated, it has nodes where amplitude is 0 and antinodes where amplitude is at a maximum

Question 55

refractive index

Answer 55

a measure of optical , ratio of the speed of light in a vacuum to the speed of light in the material

Question 56

Snell's law

Answer 56

n of medium 1 * sin(θ in medium 1) = n of medium 2 * sin(θ in medium 2)