Units and Prefixes R#2

Question 1

Units

Question 2

What is Length? And what does it describe?

Answer 2

Measurement of distance between two points. Units: metre (m), kilometre (km), centimetre (cm), millimetre (mm).

Question 3

What is Area? And what does it describe?

Answer 3

Amount of two-dimensional space enclosed by a boundary. Units: square metre (m²), square centimetre (cm²).

Question 4

What is Volume? And what does it describe?

Answer 4

Amount of three-dimensional space occupied by an object. Units: cubic metre (m³), cubic centimetre (cm³), cubic decimetre (dm³).

Question 5

What is Mass? And what does it describe?

Answer 5

Quantity of matter in an object. Units: kilogram (kg), gram (g), milligram (mg).

Question 6

What is Time? And what does it describe?

Answer 6

Interval between events. Units: second (s), minute (min), hour (h), millisecond (ms), microsecond (μs).

Question 7

What is Speed/Velocity? And what does it describe?

Answer 7

Rate of change of distance with time. Units: metre per second (m/s), kilometre per hour (km/h), centimetre per second (cm/s).

Question 8

What is Acceleration? And what does it describe?

Answer 8

Rate of change of velocity with time. Unit: metre per second squared (m/s²).

Question 9

What is Force? And what does it describe?

Answer 9

Influence that changes the motion or shape or size of an object. Unit: newton (N).

Question 10

What is Weight/Gravitational field strength? And what does it describe?

Answer 10

Force due to gravity on a mass. Units: newton (N), newton per kilogram (N/kg).

Question 11

What is Spring constant? And what does it describe?

Answer 11

Ratio of force to extension in a spring. Units: newton per metre (N/m), newton per centimetre (N/cm).

Question 12

What is Momentum? And what does it describe?

Answer 12

Product of mass and velocity. Unit: kilogram metre per second (kg·m/s).

Question 13

What is the newton-second (N·s)? And what does it describe?

Answer 13

Impulse: it is the product of force and time. It represents the change in momentum of an object. Unit: newton-second. Symbol: N·s.

Question 14

What is Impulse? And what does it describe?

Answer 14

Change in momentum resulting from a force applied over time. Unit: newton second (N·s).

Question 15

What is Moment of force? And what does it describe?

Answer 15

Tendency of a force to cause rotation about a point. Unit: newton metre (N·m).

Question 16

What is Work/Energy? And what does it describe?

Answer 16

Transfer of energy by a force acting through a distance. Units: joule (J), kilojoule (kJ), megajoule (MJ), kilowatt hour (kW·h).

Question 17

What is Power? And what does it describe?

Answer 17

Rate of doing work or transferring energy. Units: watt (W), kilowatt (kW), megawatt (MW).

Question 18

What is Pressure? And what does it describe?

Answer 18

Force applied per unit area. Units: pascal (Pa = N/m²), newton per square centimetre (N/cm²).

Question 19

What is Temperature? And what does it describe?

Answer 19

Measure of the average kinetic energy of particles in a substance. Units: degree Celsius (°C), kelvin (K).

Question 20

What is Density? And what does it describe?

Answer 20

Mass per unit volume of a substance. Units: kilogram per cubic metre (kg/m³), gram per cubic centimetre (g/cm³).

Question 21

What is Specific heat capacity? And what does it describe?

Answer 21

Energy required to raise the temperature of unit mass by one degree. Units: joule per kilogram per degree Celsius (J/(kg·°C)), joule per gram per degree Celsius (J/(g·°C)).

Question 22

What is Frequency? And what does it describe?

Answer 22

Number of complete oscillations or cycles per unit time. Units: hertz (Hz), kilohertz (kHz).

Question 23

What is Wavelength? And what does it describe?

Answer 23

Distance between successive crests or troughs of a wave. Units: metre (m), nanometre (nm), centimetre (cm).

Question 24

What is Focal length? And what does it describe?

Answer 24

Distance from the centre of a thin lens to its principal focus. Units: metre (m), centimetre (cm).

Question 25

What are Angles (incidence, reflection, refraction, critical)? And what do they describe?

Answer 25

Measure between a ray and the normal at the point of incidence. Unit: degree (°).

Question 26

What is Refractive index? And what does it describe?

Answer 26

Ratio of the sine of the angle of incidence to the sine of the angle of refraction (n = sin i/sin r). Dimensionless.

Question 27

What is Potential difference (Voltage)? And what does it describe?

Answer 27

Work done per unit charge in moving a charge between two points. Units: volt (V), millivolt (mV), kilovolt (kV).

Question 28

What is Current? And what does it describe?

Answer 28

Rate of flow of electric charge. Units: ampere (A), milliampere (mA).

Question 29

What is Electromotive force (E.M.F.)? And what does it describe?

Answer 29

Electrical work done per unit charge around a complete circuit. Unit: volt (V).

Question 30

What is Resistance? And what does it describe?

Answer 30

Ratio of potential difference across a component to the current through it. Unit: ohm (Ω).

Question 31

What is Charge? And what does it describe?

Answer 31

Quantity of electricity transported. Unit: coulomb (C).

Question 32

What is Count rate? And what does it describe?

Answer 32

Number of radioactive decays detected per unit time. Units: counts per second (counts/s), counts per minute (counts/min).

Question 33

What is a Becquerel? And what does it describe?

Answer 33

The Becquerel is the SI unit used to measure radioactivity

Question 34

What is Half-life? And what does it describe?

Answer 34

Time taken for half the nuclei in a radioactive sample to decay. Units: second (s), minute, hour (h), day, week, year.

Question 35

What is the Hubble constant? And what does it describe?

Answer 35

Ratio of the recession speed of a galaxy to its distance from us. Unit: per second (s⁻¹).

Question 36

Prefixes

Question 37

What is the prefix G? And what magnitude does it describe relative to a base unit?

Answer 37

Giga: multiplies the base unit by 10^9.

Question 38

What is the prefix M? And what magnitude does it describe relative to a base unit?

Answer 38

Mega: multiplies the base unit by 10^6.

Question 39

What is the prefix k? And what magnitude does it describe relative to a base unit?

Answer 39

Kilo: multiplies the base unit by 10^3.

Question 40

What is the prefix c? And what magnitude does it describe relative to a base unit?

Answer 40

Centi: multiplies the base unit by 10^-2.

Question 41

What is the prefix m? And what magnitude does it describe relative to a base unit?

Answer 41

Milli: multiplies the base unit by 10^-3.

Question 42

What is the prefix μ? And what magnitude does it describe relative to a base unit?

Answer 42

Micro: multiplies the base unit by 10^-6.

Question 43

What is the prefix n? And what magnitude does it describe relative to a base unit?

Answer 43

Nano: multiplies the base unit by 10^-9.