area cm , m volume cm m/s kilogram (kg), gram (g) second ... is the amount of resistance an object...

Area

Volume

Density

Force

Speed/ Velocity

Acceleration

Mass

Time

Length

Temperature

current

1 km

cm≤, m≤

cm≥, m≥, litre (l), millilitre (ml)

kg/cm≥, g/cm≥

Newton (N)

m/s, km/h

m/s≤

kilogram (kg), gram (g)

second (s)

metre (m), kilometre (km), centimetre (cm)

degrees Celsius (C∞)

ampere or amp (A)

1000m 100,000cm

1 tonne 1000kg 1000,000g

1 hour 60 minutes 3600 seconds

1 L 1000 ml 1000cm≥ of 30

Speed

o The rate of change in distance

o Is a scalar quantity

Velocity

o The rate of change in displacement

o Is a vector quantity

Type d-t v-t a-t

Gradient Velocity Acceleration

Value Displacement Velocity Acceleration

Area Displacement

How to measure gradient:

Gradient = Rise ˜ Run

Average Speed = Total Distance ˜ Total Time of 30

An object will have acceleration if:

The magnitude of velocity changes

The direction of motion changes

When describing velocity, a direction must be given.

Some objects only have two directions, e.g. backward, forward

When this happens, you can name the two directions „positive‟ and „negative‟ so that calculations are

simpler

Change in Velocity = New velocity measurement - Previous velocity measurement

Change in Velocity = V - U

Acceleration = Change in Velocity ˜ Time

Acceleration = (V - U) ˜ T

Example:

A person drives at a velocity of 40 m/s North

He accelerates, increasing his velocity to 50 m/s North in 10 seconds

o V = 5 m/s North

o U = 4 m/s North

o Change in Velocity = 5 m/s - 4 m/s

= 1 m/s North

o T = 10 seconds

o Acceleration = 1 m/s North ˜ 10 s

= 0.1 m/s≤

Example:

A ball drops and hits the ground at 5 m/s and bounces back at 3 m/s in 1 seconds

o Up = Positive

o Down = Negative

V = 3 m/s

U = -5 m/s

Change in Velocity = 3 m/s - (-5 m/s)

= 3 m/s + 5 m/s o = 8 m/s Up

T = 1 seconds

Acceleration = 8 m/s Up ˜ 1 s

8 m/s≤ Up

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Forces

A force is a push or a pull

A force is an action that can make another object change shape or change its velocity A

force is an action that can make another object accelerate

Are divided into two categories; Contact and Non-Contact

E.g. gravitational, electrostatic, twisting etc.

Friction is a contact force involving two bodies opposing each others motion

o E.g. the friction of the tyres of a car on the road cause the car to move slower

Gravitational force acts on falling objects. They reach a terminal velocity when the up

thrust is equivalent to the gravitational force.

o When objects fall, the force of gravity acts upon them o

As gravity increases, air pressure increases

o When air pressure is equal to gravity, the object travels in a straight line o

This is called terminal velocity

o This is the constant speed at which an object falls to earth

When force acts on an object, it causes the object to change the value of velocity and the direction of

movement.

EXAMPLES OF FORCE:

Weight:

The gravitational force from the earth It

acts vertically down

Normal Force:

Acts 90∞ to the surface

Is equal to weight

Friction Force:

Has the direction opposite to the direction of movement

Acts between two surfaces

Tension Force:

Acts against the deformation of a body

It takes place in a string or a rope Drag

Force:

Acts in the case of air resistance

It has the direction against motion of 30

Mass:

Is the amount of resistance an object has towards movement Is

defined as the amount of substance in an object

Force = mass ◊ acceleration

F = m x a

Weight = mass ◊ gravity

W = m x g

Gravity (10N/KG)

When force acts on an object, it causes the object to change the value of velocity and the direction of

movement.

EXAMPLES OF FORCE:

Weight:

The gravitational force from the earth It

acts vertically down

Normal Force:

Acts 90∞ to the surface

Is equal to weight

Friction Force:

Has the direction opposite to the direction of movement

Acts between two surfaces

Tension Force:

Acts against the deformation of a body

It takes place in a string or a rope Drag

Force:

Acts in the case of air resistance

It has the direction against motion

Stopping Distance

Stopping Distance = Thinking Distance + Breaking Distance

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Factors affecting thinking distance:

Thinking distance is the distance a car travels when the driver is reaction to a situation

o Alcohol

o Other drugs and some medicines

o Distraction (e.g. mobile phones)

o Speed

o Tiredness

Factors affecting braking distance

Breaking distance is the distance a car travels after the breaks have been applied

o Weather

o Condition of the road

o Speed

o Condition of tyres and breaks

Momentum = Force ◊ Perpendicular Distance from the Pivot

Force x Distance = Force x Distance

40 Newtons x 6 Metres = 80 Newtons x 3 Metres

Moment

Is a turning force

When a force causes rotation about a pivot

When System is in Equilibrium

Clockwise Moment = Anticlockwise Moment of 30

Centre of Mass

o Centre of mass is a single point in a body where all the mass appears to be

Centre of Gravity o Centre of gravity is a single point in a body where all the force of gravity appears to

act

Initial linear region of force-extension graph is associated with Hooke‟s

law

Extension is proportional to the force providing the elastic limit is not

exceeded

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Mass Kilogram (kg) Energy Joule (J)

Distance Metre (m) Speed Metre/second (m/s)

Acceleration Metre/second2 (m/s2) Force Newton (N) Time Second (s)

Power Watts (W)

Energy transfers in many ways such as:

Thermal (Heat)

Light

Electrical

Sound

Kinetic

Chemical

Nuclear

Potential (Kinetic, Elastic and Gravitational) of 30

Energy is conserved

Energy cannot be created or destroyed, only transferred.

Efficiency = Useful Energy Output ˜ Total Energy Input

Efficiency = Work ˜ Total Energy Input

Sankey Diagram

Energy transfer can take place in many ways such as:

Convection

o Heat transfers in liquids and gases

o Fluids (liquid or gas) become less dense when heated

The lower density makes the warm fluid rise and cold fluid move down

Conduction o Energy transfers through solids

o Conduction occurs when there is contact

o In metals, conduction is due to free electrons

o Bad conductors are insulators

Radiation (Infra-Red Radiation)

o It is the way energy moves through space (vacuum)

o It travels as electromagnetic waves with a speed of 300,000,000 ms-1. [3x108 ms-1]

o It needs a medium to travel through

Energy Loss at Home - Insulation

Windows

o Needs double glazing of 30

Roof

o Fibre wool insulation

Gaps o Draught excluders

Walls

o Cavity wall insulation

Marble/Stone floors

o Carpets

Work Done = Force x Distance Moved

W = F x d

Work done is always equal to energy transferred measured in Joules (J)

Work Done = Energy Transferred

Energy Transferred = Force x Distance Moved

Gravitational Potential Energy = Mass x Gravity x Height

GPE = m x g x h

Kinetic Energy = Ω x mass x speed2

KE = Ω x m x v2

Power is the rate of transfer of energy or the rate of doing work measured in Watts (W)

Power = Work Done ˜ Time Taken

P = W ˜ t

Energy transfers involved in generating electricity are:

Renewable sources of energy:

o Wind

o Water

o Geothermal Resources

o Solar Heating Systems

o Solar Cells

Non-Renewable sources of energy:

o Fossil Fuels

o Nuclear Power

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Temperature Celsius (0C) Kelvin (K)

Force Newton (N) Pressure Pascal (Pa)

Newton/ metre≤ (N/m≤) Density Kilograms/metre≥ (kg/m≥)

Grams/millilitre (g/ml) Grams/centimetre≥ (g/cm≥)

Distance Metre (m) Area Metre≤ (m≤)

Energy Joule (J) Mass Kilogram (Kg) Speed Metre/second (m/s)

Acceleration Metre/second≤ (m/s≤)

Density

Measure of mass per unit volume for any substance

KG / M≥

Density = Mass ˜ Volume

D = m ˜ V

Pressure

Measure of force per unit area

N / M≤

Pa

Pressure = Force ˜ Area

P = F ˜ a

Pressure in liquids and gases

Pressure = Density x Height x Gravity

P = D x h x g

Density of some substances:

Pure Water

o 1000 kg/m≥

Air

o 1.2 kg/m≥

Atmospheric Pressure

100 000 N/m≤

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Brownian Movement

Brown observed pollen grains moving around randomly in water

He concluded that water particles were colliding with pollen grains and causing random

motion

Brownian movement also supported the idea that gas particles are also moving in random

motion in all directions with a range of speeds

Assumptions of Kinetic Theory of Gases:

Particles are points

Particles are more in straight lines between collisions

Collisions are elastic (bounce back with same speed)

Many particles, lots of space

Continuous random motion

Boyles Law

For a fixed mass of gas, the pressure is inversely proportional to the volume if the

temperature remains constant Pressure is inversely Pressure is proportional

proportional to volume to the inverse of volume

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Charles Law

For a fixed mass of gas, the volume is proportional to the absolute temperature if the

pressure remains constant

Pressure Law

For a fixed amount of gas, the pressure is proportional to the absolute temperature if the

volume remains constant

∞ Celsius Kelvin

-273 0

0 273

100 373

As temperature increases, the speed of molecules increases

Pressure 1 x Volume 1 = Pressure 2 x Volume 2

P1 x V1 = P2 x V2

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Degree (0)

Frequency Hertz (Hz) Force Metre (m) Speed Metre/second (m/s) Time Second (s)

Transverse Waves

A transverse wave is one that vibrates, or oscillates, at right angles to the direction in which the

energy or wave is moving

Longitudinal Wave

A longitudinal wave is one in which the vibrations, or oscillations, are along the direction in

which the energy or wave is moving

Transverse Waves Longitudinal Waves

Waves Inside Fluids Surface Waves

Shock Waves Electromagnetic Waves

Seismic Waves (Underground Waves) Seismic Waves (Surface Waves)

Sound Waves Light Waves of 30

Amplitude

The maximum movement of particles from their resting position caused by a wave

Unit: A

Frequency

The number of waves produced each second by a source, or the number passing a

particular point each second

Unit: Hz (Hertz, 1 ˜ s )

Wavelength

The distance between a particular point on a wave and the same point on the next wave

(for example, from crest to crest)

Unit: λ (in metres, m )

Period

The time it takes for a source to produce one wave

Unit: T (in seconds, s )

Waves are a means of transferring energy from place to place, without the transfer of matter

Wave Speed = Frequency ◊ Wavelength

v = f ◊ λ Wave speed is measured in metres per second ( m ˜ s )

Frequency = 1 ˜ Time Period

f = 1 ˜ t

Law of reflection states that the angle of incidence is equal to the angle of reflection when light

strikes a plane mirror

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Luminous Objects

Objects that emit their own light

E.g.

o Sun

o Stars

o Fire

o Light bulbs

Non-Luminous Objects

Objects that that do not emit light

We can see them because of the light they reflect

Virtual Images

Images though which rats of light do not actually pass

Real Images

Images created with rays of light actually passing through them

Properties of an image in a plane mirror:

The image is as far behind the mirror as the object is in front Te

image is the same size as the object

The image is virtual - that is, it cannot be produced on a screen

The image is lateral invested - that is, the left side and right side of the image appear to be

interchanged

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Medium

A material through which light can travel

Speed of light:

In a vacuum and in air

o 300 000 000 m/s

In water:

o 200 000 000 m/s

Refraction

Is a property of waves changing speed (and direction) when passing a boundary

Snell‟s Law:

States that the ratio of sine angle incidence and sine angle refraction is a constant for a boundary

between two materials

n = Sin i ˜ Sin r

Refractive Index = Sin (Angle of Incidence) ˜ Sin (Angle of Refraction)

Total Internal Reflection:

Is an optical phenomenon where light (waves) refract and reflect back at a boundary of 30

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Critical Angle:

Is the angle where light reflects back and refraction is along the boundary

Sin C = 1 ˜ n

Sin (Critical Angle) = 1 ˜ Refractive Index

Reflectors

Use tiny prisms in their construction

The optical material is plastic - lighter and less fragile then a mirror of 30

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Speed of sound depends on the air (gas) temperature (since particles may be closer when

gas is cooler)

Average speed of sound in air is approximately 340 m/s

Average speed of sound in seawater is approximately 1500 m/s

Average speed of sound in a solid is approximately 5000 m/s

Audible Range for:

Humans:

o 20 Hz - 20 000 Hz

Dogs, dolphins and bats:

o Over 20 000 Hz

Infrasounds

Sounds that cannot be heard by human beings as they are produced by objects that vibrate at

frequencies lower than 20 Hz

Ultrasounds

Sounds that cannot be heard by human beings as they are produced by objects that vibrate at

frequencies higher than 20 000 Hz

Loudness

Is the measure of the power of a sound

o A wave with a big amplitude is loud

o A wave with a small amplitude is soft

Echo

A reflected sound

Echo Sounding

When ships use echoes to discover the depth of the water beneath them

Pitch

The frequency of sound waves

Measuring the Speed of Sound:

Using echoes

o (2 x distance between presentation of sound and large blank wall) ˜ time between

presentation of sound and presentation of echo

Using an oscilloscope

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Current (I) Ampere (A) Charge (Q or q) Coulomb (C)

Energy (E) Joule (J) Resistance (R) OHM (Ω)

Time (t) Second (s) Voltage (V) Volt (V) Power (P) Watt (W)

Live Wire

Provides the path along which the electrical energy from the power station travels Is

alternately positive and negative causing alternating current (ac) to flow along it

Brown in colour

Neutral Wire

Completes the circuit

Blue in colour

Earth Wire

Usually has not current flowing through it

Is there for protection if an appliance develops a fault

Green and yellow in colour of 30

Hazards of Electricity:

Frayed cables

Long cables

Damaged plugs

Water around sockets

Pushing metal objects into sockets

Safety Devices:

Fuses

o Usually in the form of a cylinder or cartridge

o Contains a thin piece of wire made from a metal that has a low melting point

If too large a current flows in the circuit, the fuse wire becomes very hot and

melts

The fuse „blows‟, shutting the circuit off

Prevents shock and reduces possibility of an electric fire

o The correct fuse to use is one that allows the correct current to flow but blows if the

current is a little larger

Trip Switches or Circuit Breakers

o If too large a current flows in a circuit, a switch opens making the circuit

incomplete

o Once the fault in the circuit is corrected, the switch is reset, usually by pressing a

reset button

Does not need to be replaced

Earth Wires

o Provides a low-resistance path for the current if and when the live wire becomes

frayed or breaks and comes into contact with the metal casing

o Prevents severe electric shock as electricity passes through a person to the earth

Double Insulation

o Is when all electrical parts of an appliance are insulated with non-conductors so

that they cannot be touched by the users o Appliances that have this do not require an earth wire

Heating elements are designed to have a high resistance

As the current passes through the element, energy is transferred and the element heats up

E.g.

o Toaster

o Kettle

o Dishwasher

o Cooker

Resistance prevents the flow of current, and causes an increase in temperature by doing so of 30

Power = Current x Voltage

P = I x V

Energy = Power x Time

E = P x t

Energy = Current x Voltage x Time

E = I x V x t

Alternating Current (ac)

The flow of electricity is constantly changing direction

Direct Current (dc)

The flow of electricity is always in the same direction

Electric Current

A flow of charge

Good Conductor of Electricity

A material through which electrons flow easily

o Electrons carry charges

Insulators

A bad conductor of electricity

Used to prevent the flow of charge of 30

Current is the rate of flow of charge

Charge = Current x Time

Q = I x t Ammeter

Used to measure the size of the current flowing in a circuit

Voltmeter

Used to measure voltage

Battery

Consists of several cells connected together

Provides current flowing in one direction (dc)

Light Emitting Diode (LED)

Fitted to many appliances to show when the appliance is switched on or on standby

Glows when current is flowing through it

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Series Circuit

No branches or junctions

One switch can turn all the components on and off together

If one bulb (or other component) breaks, it causes a gap in the circuit and all of the other

bulbs will go off

The voltage supplied by the cell or mains supply is “shared” between all the components

o The more bulbs added, the dimmer they all become

o The larger the resistance of the component, the bigger its „share‟ of the voltage

Parallel Circuit

Have branches or junctions

Switches can be placed in different parts of the circuit to switch each bulb on and off

individually, or all together

If one bulb (or other component) breaks, only the bulbs on the same branch of the circuit

will be affected

Each branch of the circuit receives the same voltage

o Even if more bulbs are added, they all stay bright

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Resistance

Is a measure of energy dissipated by charge when unit current flows All

components offer some resistance to the flow of charge

o Some circuits allow charges to pass through them very easily losing very little

energy

i.e. the components have a very low resistance

o Some circuits do not allow charges to pass through them as easily and hence lose a

significant amount of energy

i.e. the components have a very high resistance

The energy is converted into other forms, usually heat

Voltage = Current x Resistance

V = I x R

Combine Series Resistance

R = R1 + R2 + .... Rn

Combined Parallel Resistance

1 ˜ R = (1 ˜ R1) + (1 ˜ R2) + ......... (1 ˜ Rn)

Series Parallel

Voltage Divides Same

Current Same Divides

Combined Resistance High Low

Fixed Resistors

Included in circuits in order to control the sizes of currents and voltages

Variable Resistors

Allows the resistance to be altered

Thermistors

A resistor whose resistance changes quite dramatically with temperature

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o Resistance decreases as temperature increases

o E.g.

Fire alarms

Thermostats

Light-Dependant Resistors (LDRs)

Used in light sensitive circuits

o Resistance increases as light exposed increases

o E.g.

Photographic equipment

Automatic lighting controls

Burglar alarms

Diodes

A resistor that behaves like a one-way valve or one-way streets

Resistance is low to current flowing in a particular direction

Resistance is high to current flowing in the opposing direction

o Used in circuits where it is important that current flows only in one direction

o E.g.

Rectifier circuits that convert alternating current into direct current

Light Emitting Diodes (LEDs)

Diodes that glow when a current is flowing through them

OHM‟s Law

The current that flows through a conductor is directly proportional to the potential difference

across its ends, provided its temperature remains constant of 30

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area cm , m volume cm m/s kilogram (kg), gram (g) second ... is the amount of resistance an object...

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