1. 1 Forces and Motion – Units A iGCSE Edexcel 1-9 – Mr Powell
2 Electricity
3 Waves
4 Energy
5 Solid Liquids Gases
6 Magnetism
7 Radioactivity
8 Astrophysics
iGCSE Edexcel 1-9 – Mr Powell

2. 1 Forces and Motion
iGCSE
Edexcel
1-9
These are the specific units, symbols and quantities that you should know…

3. SI Units System…
A physical quantity is something that can be measured. For any measurement, the unit being used must be stated to give an understanding of the scale of the measurement.
For example, distance can be measured in kilometres or in miles. They are similar, but not the same and it is important to identify which was used for the measurement, to know how far the distance actually is.
Système Internationale d'Unités
The units that scientists use all over the world are standardised in the Système Internationale d'Unités - SI units. It is important to remember these six fundamental (or 'base') units of measurement:
metre (m) - unit of length
kilograms (kg) - unit of mass
second (s) - unit of time
ampere (A) - unit of electrical current
kelvin (K) - unit of temperature
mole (mol) - unit of the amount of substance

4. Derived SI Units System…
There are many quantities scientists measure that come from the base units. These derived units are very useful to quote as measurements, but they are not fundamental as they come from fundamental units.
For example, frequency is the number of times something happens per unit of time.
This is a useful quantity, but it is a division into the time unit.
The standard unit for frequency is considering the number 'per second', which is called 'hertz, Hz', but this comes from the fundamental unit 'second'.
Name
Unit
Abbreviation
Frequency
hertz Hz
Force
newton N
Energy
joule J
Power
watt W
Pressure
pascal Pa
Electric charge
coulomb C
Work Done or Work
Nm or J
Gravity or acceleration
Nkg-1
ms-2
g or a
Momentum
Kgms-1 p

5. 1 Forces and Motion – Units Information
iGCSE
Edexcel
1-9
Kilogram (kg): the SI unit of mass, equivalent to the international standard kept at Sèvres near Paris (approximately lb).
Metre (m): the fundamental unit of length in the metric system, equal to 100 centimetres or approximately inches.
Newton (N): the SI unit of force. It is equal to the force that would give a mass of one kilogram an acceleration of one metre per second per second.
Joule (J): the SI unit of work or energy, equal to the work done by a force of one newton when its point of application moves one metre in the direction of action of the force.
Watt (W): the SI unit of power, equivalent to one joule per second, corresponding to the rate of consumption of energy in an electric circuit where the potential difference is one volt and the current one ampere.
Speed: the rate at which someone or something moves or operates or is able to move or operate.
Acceleration (m/s/s OR Nkg-1 OR ms-2) vehicle's capacity to gain speed.