Physical Quantities

Question 1

What do most physical quantities consist of?

Answer 1

A numerical magnitude and a unit.

e.g) A current of 5A

Question 2

What are the seven fundamental quantities in the SI System?

Answer 2

Length, mass, time, electric current, temperature, amount of substance, and luminous intensity.

Question 3

What is a fundamental quantity?

Answer 3

A quantity that is arbitrarily chosen to be independent of other physical quantities and defined by means of a physical standard.

Question 4

What is the SI unit for length?

Answer 4

Metre (m)

Measured using a metre rule or measuring tape.

Question 5

What is the SI unit for mass?

Answer 5

Kilogram (kg)

Measured using a balance.

Question 6

What is the SI unit for time?

Answer 6

Second (s)

Measured using a stopwatch.

Question 7

What is the SI unit for temperature?

Answer 7

Kelvin (K)

Measured using a thermometer.

Question 8

What is the SI unit for electric current?

Answer 8

Ampere (A)

Measured using an ammeter.

Question 9

What is the SI unit for amount of substance?

Answer 9

Mole (mol)

Question 10

What is the SI unit for luminous intensity?

Answer 10

Candela (cd)

Measured using a photometer.

Question 11

What is a mole defined as?

Answer 11

Containing exactly 6.02214076×10²³ elementary entities.

Question 12

What are derived quantities?

Answer 12

Physical quantities related to fundamental quantities by mathematical and scientific definitions.

Question 13

What is the formula for speed?

Answer 13

Speed = Distance ÷ Time

Question 14

What is the formula for force?

Answer 14

Force = Mass x Acceleration

Question 15

What is the derived unit for area?

Answer 15

Square metre (m²)

Area = Length x Breadth.

Question 16

What is the derived unit for volume?

Answer 16

Cubic metre (m³)

Volume = Length x Breadth x Height.

Question 17

What is the derived unit for density?

Answer 17

Kilogram per cubic metre (kg/m³)

Density = Mass ÷ Volume.

Question 18

What is the derived unit for velocity?

Answer 18

Metre per second (m/s)

Velocity = Displacement ÷ Time.

Question 19

What is the derived unit for acceleration?

Answer 19

Metre per second squared (m/s²)

Acceleration = ∆ Velocity ÷ Time.

Question 20

What is the derived unit for pressure?

Answer 20

Pascal (Pa)

Pressure = Force ÷ Area.

Question 21

What is the derived unit for energy?

Answer 21

Joule (J)

Energy = Force x Displacement.

Question 22

What is the derived unit for power?

Answer 22

Watt (W)

Power = Energy ÷ Time.

Question 23

What is the SI system based on?

Answer 23

A decimal system where units are multiplied or divided by 10.

Question 24

What is scientific notation?

Answer 24

A way of writing numbers in the form a x 10^b, where ‘a’ is a real number between 1 and 10 and ‘b’ is an integer.

Question 25

What are significant figures?

Answer 25

Digits that carry meaning contributing to a measurement's resolution.

Question 26

What are the rules for significant figures?

Answer 26

Non-zero digits are always significant, zeros between nonzero digits are significant, leading zeros are not significant, and trailing zeros are significant if there is a decimal point.

Question 27

How many significant figures are in 81?

Answer 27

2

Question 28

How many significant figures are in 0.007?

Answer 28

1

Question 29

How many significant figures are in 5200.38?

Answer 29

6

Question 30

How many significant figures are in 78800?

Answer 30

3

Question 31

How many significant figures are in 78800.?

Answer 31

5