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

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

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

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

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 2.205 lb). Metre (m): the fundamental unit of length in the metric system, equal to 100 centimetres or approximately 39.37 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.