| SI Units | ||
| Quantity | Unit | Symbol |
| Mass | Kilogram | KG |
| Force | Newton | N |
| Weight | Newton | N |
| Pressure | Pascal | Pa |
| Energy | Joules | J |
| Work | Joules | J |
| Power | Watt | W |
| Frequency | Hertz | Hz |
| PD, EMF | Voltage | V |
| Current | Amperes | A |
| Resistance | Ohms | (Omega) |
| Charge | Coulombs | C |
| Specific Heat capacity | Joules per kilogram Celsius | J/KgC |
| Specific Heat Latent | Joules per Kilogram | J/KG |
| Temperature | Kelvin/ Celsius | K Or C |
1.1- Measuring Time And Length
Measuring Length-Micrometer ( Use 10 sheets of paper for accuracy)
Measuring Time- E.g. : one swing of pendulum ( Find the times for 25 swings for accurate results)
Example of Scalar qualities-Time, Volume, Speed, temperature
Example of Vector qualities- Velocity, Change in Temperature, acceleration, force, momentum
1.2- Mass, weight, volume and density
Density= Mass/ Volume
Mass: the property of an object that is a measure of its inertia (a resistance to accelerate), the amount of matter it contains, and its influence in a gravitational field.
Weight is the force of gravity acting on an object, measured in Newtons, and given by the formula: Weight = mass × acceleration due to gravity
Measuring volume
Liquid- Level on the scale Regular object(Square box) – Ruler
Irregular Object(Rock)- Lower into a partly filled measuring cylinder, Rise in level on the volume scale gives the volume of solid. Alternative method – Displacement Can (Fill water to level of spout, insert object, water displaced = volume of object)
1.3- Speed, velocity, Acceleration
Speed= distance/time
Acceleration= Change in velocity/ time taken
Velocity= Vector ( Magnitude + direction) Speed= Scalar ( Magnitude only)
Distance Time Graph
Constant gradient= constant speed increasing gradient= acceleration
Zero gradient= stopped Gradient= Speed of object
Speed Time Graph
Zero gradient= Constant speed Constant gradient= steady acceleration
Gradient of graph= Acceleration Distance= Area under graph
Positive increase of speed= Acceleration Negative increase of speed= Retardation
Acceleration of Free fall= gravitational field strength in Earth = 10
Terminal Velocity
Downward acceleration is caused by Gravitational field strength; Air resistance slow things down. Once air resistance is equal to Gravitational field strength, it is at terminal velocity ( Constant Velocity)
1.4- Forces
Hooke’s Law
The extension of an object is proportional to the load beneath its elastic limit.
Load= Spring constant x extension
Limit of proportionality= point at which load and extension are no longer proportional
Elastic limit= Spring will be permanently stretched
Newton’s first law of motion= If no external for is acting on it, an object will, if stationary, remain stationary, and if moving, keep moving at a steady speed in the same straight line
Newton’s 2nd law of motion: F = m × a -acceleration is proportional to the force, and inversely proportional to mass
Newtons 3rd law of motion: if object A exerts a force on object B, then object B will exert an equal but opposite force on object A
Centripetal Force and Centrifugal Force
Circular motions- An object at steady speed in a circular orbit is always accelerating as its direction is changing, but it gets no closer to the centre
Centripetal force- Force acting towards centre of circle
Centrifugal force- Force acting outwards the centre of circle.
Magnitude of centripetal and centrifugal is the same but direction is opposite
Centripetal force increase when mass, speed and radius increase
1.5- Turning Effects
Moment of a force= force x perpendicular distance from the point
Moments of a force are measured in Newton meters, can be either clockwise or anticlockwise.
Conditions of equilibrium= no net moments, sum of clockwise moment is equal to the sum of anticlockwise moment.
1.6 – Energy, Work and Power
Key terms and formulas: KE- 1/2MV^2 GPE- MGH
Law of conservation of energy- Energy cannot be made or destroyed, but it can change from one form to another.
Types of energy:
| Energy Type | What is it? | Example |
| Kinetic Energy | Energy due to a motion | A moving object |
| Gravitational Energy | Energy from potential to fall | A book on shelf |
| Chemical Energy | Energy stored in chemical bonds | Food, Batteries |
| Strain or elastic Energy | Something stretched has the potential to do work | Compressed string |
| Nuclear Energy | Energy released when particles in atoms are rearranged or when atom splits | Nuclear Power station |
| Internal Energy | Kinetic + Potential Energy | – |
| Electrical energy | Energy carried by electrons | Bulb |
| Radiated Energy:Light | Energy carried in light waves | Light from sun |
| Sound | Energy carried in sound waves | Sounds from loudspeaker |
Energy Resources
Renewable source- Sources that won’t run out
Non-renewable source- Sources that would be extinct in a certain number of time
fuels can be burnt (or nuclear fuel can be forced to decay) in thermal power stations to transform the chemical energy stored to thermal energy which makes steam which turns turbines (kinetic energy) to produce electricity
advantage: cheap, plentiful, low-tech
disadvantage: harmful wastes -produces greenhouse gases and pollutant gases, radiation
hydroelectric dams: river and rain water fill up a lake behind a dam. As water rushes down through the dam, it turns turbines which turn generators
tidal power scheme: a dam is built across a river where it meets the sea. The lake behind the dam fills when the tide comes in and empties when the tide goes out. The flow of water turns the generator.
advantage: no greenhouse gases are produced
disadvantage: expensive, can’t be built everywhere
wave energy: generators are driven by the up and down motion of the waves at sea.
advantage: does not produce greenhouse gases
disadvantage: difficult to build
geothermal resources: water is pumped down to hot rocks deep underground and rises as steam.
advantage: no carbon dioxide is produced
disadvantage: deep drilling is difficult and expensive
nuclear fission: uranium atoms are split by shooting neutrons at them.
advantage: produces a lot of energy from using very little resources
disadvantage: producing radioactive waste
solar cells: are made of materials that can deliver an electrical current when they absorb light energy solar panels: absorb the energy and use it to heat water
advantage: does not produce carbon dioxide
disadvantage: variable amounts of sunshine in some countries
Efficiency, Work and Power Formulas
Efficiency= useful work done/ total energy input
Work done= Force x Distance
Power= Work Done/ Time
1.7 – Pressure
Pressure = Force / area
To reduce pressure- Increase surface area of base
Pressure in liquid
Pressure= density x g(10) x height
Characteristic of pressure in liquids:
-Pressure acts in all directions
-Pressure increase with depth
-Pressure depends on the density of liquid
-Pressure doesn’t depend on the shape of the container
Pressure from the air
Barometers measure atmospheric pressure, standard atmospheric pressure = pressure that supports a column of 760mm of mercury (101300 Pa)
Manometer measures pressure difference, height difference in manometer shows extra pressure. Actual pressure of gas supply = excess pressure + atmospheric pressure.
Gas Pressure and Volume
For a fed mass of gas at a constant temperature, the pressure is inversely proportional to the volume. (Boyle’s Law)
Pressure and Volume are inversely proportional ( volume halves = pressure double)
P1V1=P2V2
Pressure x volume always has the same value
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