Unit 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

Kilogram (Kg)

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 C° 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

Are Newtons (N) an SI unit?

Answer 7

No newtons are not fundamental. The SI units for force are kg·m·s‑2. (Since force= mass x acceleration).

Question 8

Derive the SI units of energy.

Answer 8

Kinetic energy = ½ × mass × velocity²
Units = kg x (m/s) x (m/s)
= Kg m² s⁻²

Question 9

Derive the SI units of force.

Answer 9

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

Question 10

Express 60TΩ in standard form.

Answer 10

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

Question 11

Write 0.000003m with a suitable prefix.

Answer 11

3µm (3 micro meters) (The factor of micro is 10⁻⁶ so move the decimal place 6 times to the right).

Question 12

What is the actual value of 8MΩ?

Answer 12

8,000,000Ω or 8x10⁶Ω

Question 13

What is Ω?

Answer 13

Resistance (gwrthiant)

Question 14

What is 6000pF in nF? (p=10⁻¹² and n=10⁻⁹)

Answer 14

6nF as 1 nano unit is 1000 pico units.

Question 15

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

Answer 15

x1000 (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 10⁹ Ω

Question 18

What is 1 eV in J?

Answer 18

1eV = 1.6 x 10⁻¹⁹ J

Question 19

Equilibrium

Answer 19

A body is in equilibrium if it’s moving and rotating at a constant rate. (Can be still).

1. The resultant force on the object must be zero
   2.The resultant moment (about any point) must be zero (the principle of moments).

Question 20

Principle of moments

Answer 20

When a body is balanced, the total clockwise moment about a point equals the total anticlockwise moment about the same point.

Question 21

In order for an object to be in equilibrium (2)

Answer 21

1. The resultant force on the object must be zero
   2.The resultant moment (about any point) must be zero (the principle of moments).

Question 22

The turning effect of a force is often referred to as ___________ or torque.

Answer 22

moment

Question 23

The moment of a force about a point is defined as the force multiplied by the ___________ distance from the point to the line of action of the force.

Answer 23

perpendicular

Question 24

If the size of the force is increased, then the moment will ___________.

Answer 24

increase

Question 25

A force may cause a clockwise moment or an __________ moment.

Answer 25

anti-clockwise

Question 26

The principle of moments can be applied to any object which is in ___________.

Answer 26

equilibrium.

Question 27

Explain, using your understanding of moments, why it may be easier to use a longer spanner rather than a shorter one to loosen a nut.

Answer 27

With a longer spanner the perpendicular distance from the pivot to the line of action of the force will be greater. This means that for any given force, the moment (turning effect) will be greater.