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 Time E.g. : one swing of pendulum ( Find
the times for 25 swings for accurate results)
Example of Scalar qualitiesTime, 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

Sound from
loudspeaker

Energy Resources
Renewable source Sources that won't run
out
Nonrenewable 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, lowtech
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
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

Next Topic
Topic 1 General Physics
Topic 2 Thermal Physics
Topic 3 Properties of Waves, Including Sound and Light
Topic 4 Electricity and Magnetism
Topic 5 Atomic Physics


Next Topic
Topic 1 General Physics
Topic 2 Thermal Physics
Topic 3 Properties of Waves, Including Sound and Light
Topic 4 Electricity and Magnetism
Topic 5 Atomic Physics

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