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 Ã— acceleration due to gravity

Measuring volume

Liquid- Level on the scaleÂ Â Â Â Â Â 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

Acceleration= Change in velocity/ time taken

Velocity= Vector ( Magnitude + direction)Â Â Â Â Â Speed= Scalar ( Magnitude only)

Velocity= Vector ( Magnitude + direction)Â Â Â Â Â Speed= Scalar ( Magnitude only)

__Distance Time Graph__Constant gradient= constant speedÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â increasing gradient= acceleration

Zero gradient= stoppedÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Gradient= Speed of object

__Speed Time Graph__

Zero gradient= Constant speedÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Constant gradient= steady acceleration

Gradient of graph= AccelerationÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Distance= Area under graphÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â

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 LawHooke’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

Newtonâ€™s 2nd law of motion**: F = m Ã— 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=Â **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:Â

**KE- 1/2MV^2Â Â Â Â Â Â Â Â Â Â Â Â Â Â 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

Non-renewable source- Sources that would be extinct in a certain number of time

**Â 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**

__fuels__**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, canâ€™t be built everywhere

** wave energy**: generators are driven by the up and down motion of the waves at sea.Â

**advantage:**Â 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:**Â variable amounts of sunshine in some countries__Efficiency, Work and Power Formulas__Efficiency= useful work done/ total energy input

Work done= Force x Distance

Work done= Force x Distance

Power= Work Done/ Time

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__**, standard atmospheric pressure = pressure that supports a column of 760mm of mercury (101300 Pa)**

__Barometers measure atmospheric pressure__

**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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