Definitions (ALL)

Question 1

Define physical quantity

Answer 1

A quantity that can be measured and consists of magnitude and unit

Question 2

Define base quantities

Answer 2

A set of independent physical quantities

Question 3

Define oscillation(pendulum)

Answer 3

The regular repeating, back-and-forth motion of a simple pendulum

Question 4

Define period of oscillation

Answer 4

Time taken for one complete oscillation

Question 5

Define incident ray

Answer 5

The light ray going towards the surface

Question 6

Define reflected ray

Answer 6

The light ray going away from the surface

Question 7

Define point of incidence

Answer 7

The point at which incident ray strikes the surface

Question 8

Define normal

Answer 8

The perpendicular line to the surface at the point of incidence

Question 9

Define angle of incidence

Answer 9

The angle between the incident ray and the normal

Question 10

Define angle of reflection

Answer 10

The angle between the reflected ray and the normal

Question 11

Define refraction

Answer 11

Refraction is the bending of light as it passes from one medium to another medium of different optical density

Question 12

Define refracted ray

Answer 12

Light ray that enters a medium and undergoes a change of direction

Question 13

Define refractive index

Answer 13

The ratio of speed of light in vacuum to speed of light in medium

Question 14

Define total internal reflection

Answer 14

Complete reflection of a light ray in an optically denser medium at the boundary with an optically less dense medium

Question 15

Define critical angle c

Answer 15

The angle of incidence in optically denser medium for which angle of refraction in optically less dense medium is 90

Question 16

Define lens

Answer 16

A piece of clear plastic or glass with curved surface for concentrating or dispersing light rays

Question 17

Define focal length of converging lens

Answer 17

The distance between optical centre C and principal focal point F (on the principal axis where the rays parallel to the principal axis meet after passing through the lens) - 2m

Question 18

Define ionising radiation

Answer 18

Radiation that has the energy to remove electrons from atoms or molecules, thereby ionising them

Question 19

Define wave

Answer 19

A wave is a disturbance that propagates through space, transferring energy with it but not matter

Question 20

Define transverse wave

Answer 20

A transverse wave has a direction of vibration that is perpendicular to direction of wave travel

Question 21

Define longitudinal waves

Answer 21

A longitudinal wave has direction of vibration parallel to direction of wave travel

Question 22

Define amplitude of wave

Answer 22

The maximum displacement of a point from its rest position

Question 23

Define wavelength

Answer 23

The shortest distance between any two points of a wave which are in a phase

Question 24

Define displacement-distance graph

Answer 24

A plot of displacements of all points of a wave at an instant

Question 25

Define period of wave

Answer 25

The time taken to produce one complete wave

Question 26

Define frequency of wave

Answer 26

The number of complete waves produced per unit time

Question 27

Define wave speed

Answer 27

The distance travelled by the wave per unit time

Question 28

Define wavefront

Answer 28

An imaginary line on a wave that joins all adjacent points that are in phase

Question 29

Define sound

Answer 29

A longitudinal wave travelling in a medium, created by a vibrating source

Question 30

Define echo

Answer 30

The repetition of sound due to the reflection of sound

Question 31

Define ultrasound

Answer 31

Ultrasound is sound with frequencies above the upper limit of the human range of audibility

Question 32

Define speed

Answer 32

Speed is the distance travelled per unit time

Question 33

Define velocity

Answer 33

Velocity is the rate of change in displacement

Question 34

Define average speed

Answer 34

Average speed assumes an object moves at same speed throughout entire distance

Question 35

Define instantaneous speed

Answer 35

Speed of an object at a particular instant

Question 36

Define acceleration

Answer 36

The rate of change of velocity

Question 37

Define scalar quantity

Answer 37

Physical quantities that only have magnitude

Question 38

Define vector quantity

Answer 38

Physical quantities that have both magnitude and direction

Question 39

Define mass

Answer 39

A measure of the amount of matter in a body

Question 40

Define weight

Answer 40

The gravitational force acting on an object that has mass

Question 41

Define gravitational field

Answer 41

A region in which mass experiences a force due to gravitational attraction

Question 42

Define gravitational field strength

Answer 42

The gravitational force per unit mass placed at that point

Question 43

Define inertia

Answer 43

Inertia of an object is the reluctance of the object to change its state of rest or motion due to its mass

Question 44

Define friction

Answer 44

Friction is the contact force that opposes or tends to oppose motions between surfaces in contact

Question 45

Define moment of a force

Answer 45

The product of the force and perpendicular distance from the pivot to the line of action of the force

Question 46

Define centre of gravity

Answer 46

The point at which the weight of the object appears to act

Question 47

Define stability

Answer 47

The ability to return to its original position after it is slightly displaced

Question 48

Define internal energy of a substance

Answer 48

The sum of kinetic energy due to the random motion of particles and potential energy due to forces of attraction between the particles

Question 49

Define kinetic energy

Answer 49

Kinetic energy is the energy a body possess due to its motion

Question 50

Define gravitational potential energy

Answer 50

The energy a body possess due to its position relative to a reference level, usually the ground.

Question 51

Define work done

Answer 51

Energy transferred mechanically by force acting over a distance

Question 52

Define power

Answer 52

Power is rate of work done or rate of energy transfer

Question 53

Define density

Answer 53

Density of a substance is its mass per unit volume

Question 54

Define pressure

Answer 54

Force acting per unit area

Question 55

Define heat capacity

Answer 55

The amount of heat required to raise the temperature of a substance by 1K or 1C

Question 56

Define specific heat capacity

Answer 56

Specific heat capacity is the amount of heat required to raise the temperature of a unit mass of a substance by 1K or 1C

Question 57

Define melting

Answer 57

The change from solid state to liquid state when energy is transferred to the substance. During this process, temperature of pure substance remains constant

Question 58

Define boiling

Answer 58

Boiling is change from liquid state to gaseous state when energy is transferred to the substance. During the process, temperature of a pure substance remains constant

Question 59

Define latent heat

Answer 59

The energy released or absorbed to change the state of a substance at a constant temperature

Question 60

Define latent heat of fusion/vapourisation

Answer 60

The amount of heat required/released to change a substance between the solid/liquid and liquid/gas states, at constant temperature

Question 61

Define specific heat of fusion/vapourisation

Answer 61

The amount of heat required/released to change a unit mass of substance between solid/liquid and liquid/gas states, at constant temperature