1.1 Basic Physics

Question 1

What are SI units?

Answer 1

Fundamental (base) units of physical quantities.

Question 2

What is the SI unit of mass?

Answer 2

Kg (kilogram)

Question 3

What physical quantity is measured in mol?

Answer 3

Amount of a substance.

Question 4

What is the SI unit of current?

Answer 4

Amperes (A)

Question 5

Is the SI unit for temperature oC or K ?

Answer 5

K (kelvin) as this is the absolute scale.

Question 6

What is the SI unit of length?

Answer 6

Metres (m)

Question 7

What quantity is measured in seconds?

Answer 7

Time.

Question 8

Are Newtons (N) an SI unit?

Answer 8

No, Newtons are not fundamental. The SI units for force are kg m s-2 (Since force = mass x acceleration).

Question 9

Derive the SI units of energy.

Answer 9

Kinetic energy = 1⁄2 x mass x velocity2 Units = kg x (m/s) x (m/s)
= kg m2 s-2

Question 10

Derive the SI units of force.

Answer 10

Force = mass x acceleration Units = kg x m s-2
= kg m s-2

Question 11

Express 60TΩ in standard form.

Answer 11

6 x 1013
(T is tera and the multiplier is 1012)

Question 12

Write 0.000003m with a suitable prefix.

Answer 12

3μm

Question 13

What is the actual value of 8MΩ?

Answer 13

8,000,000Ω or 8x106Ω

Question 14

What is 6000pF in nF?

Answer 14

6nF, as 1 nano unit is 1000 pico units.

Question 15

What multiplier is associated with the prefix kilo (k)?

Answer 15

x 1000 (103)

Question 16

What multiplier is associated with the prefix femto (f)?

Answer 16

10^(-15)

Question 17

Express 7GΩ in standard form

Answer 17

7 x 10(9) Ω

Question 18

What is 1 eV in J?

Answer 18

1eV = 1.6 x 10-19 J

Question 19

Express 6 kWh in joules.

Answer 19

6 kW = 6000 J/s
1 hour = 3600s
6kWh = 6000 x 3600
= 21.6 x 106 J
= 21.6 MJ

Question 20

Convert 6.6 pJ to eV.

Answer 20

6.6 pJ = 6.6 x 10-12 J
7.Divide by 1.6 x 10-19
6.6 pJ = 4.1 x 107 eV (2s.f.)
= 41 MeV

Question 21

What is meant by a scalar quantity?

Answer 21

A quantity that only has a magnitude.

Question 22

What is a vector quantity?

Answer 22

A quantity that has magnitude as well as direction.

Question 23

Is acceleration a vector or scalar quantity?

Answer 23

Vector.

Question 24

Is mass a scalar or vector quantity?

Answer 24

Scalar.

Question 25

Answer 25

Question 26

Answer 26

Question 27

Answer 27

Question 28

What equation is used to calculate density?

Answer 28

ρ = m /V
Density = Mass / Volume
Density units: kg m-3
Mass units: kg
Volume units: m3

Question 29

What is a moment?

Answer 29

A turning force.
Force × perpendicular distance from the point to the line of action of the force

Question 30

If an object is in equilibrium, the sum of the anticlockwise moments would be…

Answer 30

Equal to the sum of the clockwise moments (principle of moments).

Question 31

If an object is in equilibrium it means the object is …

Answer 31

Not accelerating. It is either:
● Stationary.
● Moving at a constant velocity.

Question 32

How can the forces acting on a object be shown to be in equilibrium?

Answer 32

●Adding the horizontal and vertical components of the forces acting on it and showing they equal zero.
●Or if there are 3 forces acting on the object you can draw a scale diagram - if the scale diagram forms a closed triangle, then the object is in equilibrium.

Question 33

What is meant by a couple?

Answer 33

A pair of equal and opposite coplanar forces that have equal magnitude and opposite direction, applied to a body parallel to each other but not along the same line. For example: