Definitions

Question 1

Refraction

Answer 1

Refraction is the bending of light as it goes from one medium to another.

Question 2

Laws of Refraction

Answer 2

(1) Incident ray, refracted ray & normal are on the same plane.
(2) Sine I/Sine R is constant.

Question 3

Refractive Index

Answer 3

Sine I/Sine R = 1/Sin C = Real depth/Apparent depth = c1/c2

Question 4

Critical Angle

Answer 4

The angle whose angle of incidence is 90 when light goes from a denser
to a rarer medium.

Question 5

Total Internal Reflection

Answer 5

When light travelling from a denser to a rarer medium strikes the second medium with an angle of incidence greater than the critical angle, it is reflected back.

Question 6

Acceleration

Answer 6

Acceleration is the rate of change of velocity per unit time.

Question 7

Newton’s laws

Answer 7

1. A body will remain in a state of rest or travelling at a constant velocity unless an external force acts on it.
2. When an unbalanced force acts on a body, the rate of change of the body’s momentum is directly propotional to the foce and takes place in the direction of the force. [ F ≈ (mv-
   mu)/t –> F = km(v-u)/t –> F = kma –> F = ma ]
3. Every action has an equal and opposite reaction.

Question 8

Pressure

Answer 8

Pressure is force per unit area. P = F/A -> Due to liquid: P = pgh

Question 9

Archimedes’ Principle

Answer 9

Archimedes’ Principle states that when an object is partially or completely immersed in a fluid it experiences an upthrust equal in magnitude to the weight of the fluid displaced.

Question 10

Law of Flotation

Answer 10

Law of Flotation states that the weight of a floating body is equal to the weight of the fluid it displaces.

Question 11

Boyle’s law

Answer 11

Boyle’s law states that at constant temperature the volume of a fixed mass of gas is inversely proportional to to its pressure.

Question 12

Newton’s Law of Universal Gravitation

Answer 12

Newton’s Law of Universal Gravitation states that any two point masses in the universe attract each other with a force that is directly proportional to the product of their
masses and inversely proportional to the square of the distance between them.

Question 13

Moment

Answer 13

Moment = Force x Perpendicular distance

Question 14

Couple

Answer 14

Two parallel forces with the same magnitude acting in opposite directions.

Question 15

Torque (Moment of a couple)

Answer 15

T = Fd

Question 16

Work

Answer 16

Work = Force x Displacement (Joule = Newton Meter)

Question 17

Energy

Answer 17

Energy is the ability to do work.

Question 18

Principle of Conservation of Energy

Answer 18

Principle of Conservation of Energy states that energy cannot be created or destroyed
but can only be converted from one form to another.

Question 19

Ek

Answer 19

Ek = 1/2mv2

Question 20

Ep

Answer 20

Ep=mgh

Question 21

Power

Answer 21

Power = Work done ÷Time taken || P = w ÷ t (Watt = Joule/Second)

Question 22

Percentage Efficiency

Answer 22

Percentage Efficiency = (Output/Input) x 100

Question 23

Angular Velocity

Answer 23

Angular Velocity is the rate of change of angle per unit time.

Question 24

Centripetal Force

Answer 24

Centripetal Force: If a body is moving in a circle, the force towards the centre needed to
keep it moving is centripetal force.

Question 25

Centripetal Acceleration

Answer 25

Centripetal Acceleration is acceleration a body has towards the centre of the circular path it is moving on.

Question 26

Period of an Orbit

Answer 26

Period of an Orbit is the time taken for a satellite to go once around the central body.

Question 27

A body is said to be moving with simple harmonic motion if:

Answer 27

1. It’s acceleration is directly proportional to its distance from a fixed point on its path.
2. Its acceleration is always directed towards that point.

Question 28

Hooke’s law

Answer 28

Hooke’s law states that when an object is bent, stretched or compressed by a
displacement ‘s’, the restoring force ‘F’ is directly proportional to the displacement – provided the elastic limit is not exceeded.

Question 29

Temperature

Answer 29

Temperature is the measure of the hotness or coldness of a body.

Question 30

Thermometric properties

Answer 30

Thermometric properties are any physical properties that change measurably with
temperature.

Question 31

Specific Heat Capacity

Answer 31

Specific Heat Capacity of a substance is the heat energy needed to change the temperature of 1kg of the substance by 1K. (J/kg/K)

Question 32

Specific Latent Heat

Answer 32

Specific Latent Heat of a substance is the amount of heat energy needed to change the
state of 1kg of that substance without changing its temperature. (J/kg)

Question 33

Conduction

Answer 33

Conduction is the movement of heat energy through a substance by the passing on of molecular vibration from molecule to molecule. There is no overall motion of the substance.

Question 34

Convection

Answer 34

Convection is the transfer of heat through a fluid by means of circulating currents of fluid caused by the heat.

Question 35

Radiation

Answer 35

Radiation is the transfer of heat energy from one place to another in the form of electromagnetic waves.

Question 36

U Value

Answer 36

U Value of a structure is the amount of heat energy lost per second through 1m2 of the structure when a temperature difference of 1K is maintained between its ends.

Question 37

Solar Constant

Answer 37

Solar Constant is the average amount of the sun’s energy falling per second perpendicularly on 1 m2 of the earth’s atmosphere. 1.35 kW/m2

Question 38

Transverse wave

Answer 38

Transverse wave is a wave where the direction of the wave is perpendicular to the direction of vibration.