IGCSE Physics (Co-ordinated Sciences Double Award 2024)

Acceleration (m/s^2)

change in velocity (m/s) / time taken (s)

Density (g/cm³ or kg/m³)

Mass (g or kg) / Volume (cm³ or m³)

How can you find accurate measurements of small things? eg a sheet of paper

measure a lot of them and divide by the number u measured

How can I make my experiment results accurate?

Do lots of trials, do trials until the average does not change with each trial

Speed

rate of change of distance

Speed (m/s)

distance (m) / time (s)

Instentaneous Speed

The rate at which an object is moving at a given moment in time

Velocity

Speed in a given direction

scalar quantity

A physical measurement that does not contain directional information

vector quantity

a quantity that has both magnitude and direction

Examples of scalar quantities

speed, distance, mass,
temperature, energy

Examples of vector quantities

force, velocity, displacement, acceleration, weight

Acceleration

rate of change of velocity over time

Instantaneous speed on a distance-time graph

draw a tangent and find the gradient

average speed on a distance-time graph

gradient or draw a line across and down

Acceleration on a speed-time graph

gradient of line

distance on a speed-time graph

area under the line

mass

the amount of matter in an object, how difficult it is to move something

how to determine which object is heavier in space

which is harder to push

Weight (N)

mass (kg) x gravitational field strength (N/kg)

weight

the pull of gravity on an object

inertia

How difficult it is to change the motion of an object

Density

Mass per unit volume

System

a group of objects that interact

Hooke's Law equation

F=kx (force = constant x extension) constant= spring constant/stiffness

Limit of proportionality

When an elastic object is stretched beyond its limit of proportionality, the object does not return to its original length when the force is removed.

Limit of elasticity

maximum stress or force per unit area within a solid material that can arise before the onset of permanent deformation

directly proportional graph

the graph is linear and passes through the origin

plastic deformation

permanent change in shape, the spring will not go back to its original shape

Hooke's Law in words

The extension of a spring is directly proportional to the load applied to it, provided the limit of proportionality is not exceeded

directly proportional

the relationship between two variables whose ratio is a constant value

1dm^3

1000cm^3, 1L

Density of water

1 g/cm³ or 1000 kg/m³

To convert from m/s to km/h

multiply by 3.6

Acceleration of free fall

g=10m/s^2

k

tells us how much force is required for 1 cm or m

Resultant force

mass x acceleration

moment (Nm)

force (N) x perpendicular distance from pivot (m)

Friction

A force that acts to oppose motion, or the tendency to motion, and creates heat

terminal velocity

The maximum speed of an object due to air resistance

Newton's First Law

when forces are balanced, there is no acceleration. This means that an object is either stationary or moving at a constant velocity

Newton's Second Law

When forces are unbalanced, the object accelerates and either the speed changes or the direction changes

free body diagram

a diagram showing all the forces acting on an object

Free body diagram things to remember

you can not tell the direction an object is moving, you can only tell its acceleration. When the question asks to describe the motion it wants the acceleration. Acceleration is always in the direction of the biggest force

calculating moments

don't forget to convert kg to N

Principle of moments

For a body in rotational equilibrium, the sum of the anticlockwise moments about a point is equal to the sum of the clockwise moments about the same point

moments are used in

hammers, levers, spanners, etc.

A system is in equilibrium when

resultant force and moment equal

to find center of mass

line of symmetry, line above pivot

pressure (N/cm^2, N/m^2 (Pa))

force (N)/area (cm^2, m^2)

N/cm2 to N/m2

x 10,000

pressure

Force per unit area.

lower center of mass

more stable object

stable equilibrium

movement results in center of mass going up

unstable equilibrium

movement results in the center of mass going down

neutral equilibrium

movement does not result in the center of mass moving

plumb line

A string with a weight used to provide a vertical reference line, like when finding COM of irregular plane lamina

Energy

The ability a physical system has to do work on other physical systems

Work done

force x distance moved in direction of force

kinetic energy

the energy an object has due to its motion

gravitational potential energy

potential energy based on an object's position in gravitational field

chemical potential energy

stored in food, fuel, released by chemical reactions

elastic potential energy

Energy stored by something that can stretch or compress

nuclear energy

stored in nuclei

TYPE OF ENERGY kinetic

converted from chemical, process car engine

TYPE OF ENERGY gravitational potential

converted to kinetic, process falling down

TYPE OF ENERGY elastic potential (strain)

converted to kinetic, process catapult

TYPE OF ENERGY nuclear

converted to kinetic, process bomb

TYPE OF ENERGY thermal

converted to kinetic, process gas power station

TYPE OF ENERGY light

converted to electrical, process solar cell

TYPE OF ENERGY sound

converted to electrical, process microphone

TYPE OF ENERGY electrical

converted from chemical, process battery

TYPE OF ENERGY chemical

converted from light, process photosynthesis

Kinetic Energy (KE)

1/2mv^2, mass must be in kg!

gravitational potential energy (GPE)

mg change in h

Law of Conservation of Energy

Energy cannot be created or destroyed, it may be transformed from one form into another, but the total amount of energy never changes

if you cant identify what the energy has changed into

put thermal

Efficiency

Useful energy output / total energy input x 100%

Power (J/s or W)

energy converted (could be given as work done, GPE or KE)/time taken (s)

Kelvin scale

celcius + 273

how does temperature affect gas pressure

raising the temperature of a gas will increase its pressure

How does volume affect gas pressure?

Reducing the volume of a gas increases its pressure

Boyle's Law

pressure and volume are inversely proportional

Brownian motion

evidence that molecules are moving around randomly and banging into larger things causing them to move. Evidence of kinetic theory. Based on observations of the movement of smoke in the air or pollen in water.

Internal energy

total kinetic and bond energy (potential) or all the particles in a substance, stored in hot objects

why are there flat parts on a heating/cooling curve?

because the temperature does not increase as all of the KE is being used to break the bonds between the atoms

when bonds are broken

potential energy is increased

melting point for water, boiling point for water

0ºc, 100ºc

3 factors of evaporation

temperature, surface area, draught

conduction

happens in solids by free electrons passing energy to other atoms

good conductors, bad conductors

metal, plastic wood glass

Convection

Process by which, in a fluid being heated, the atoms get more energy and move around more, they become more spread out and less dense and therefore rise, the cooler denser air replaces it and it creates a current.

infrared radiation

can go through a vacuum or some gasses, not greenhouse gasses, can be reflected and absorbed

speed of light (and all electromagnetic waves)

300,000,000 m/s

Best emitter and absorber of infrared

matt black

worst emitter and absorber of infrared

shiny white (silver)

why is it important to not waste energy?

wastes limited resources, bad for the environment, costs money

sun is the source of all energy resources except for

geothermal nuclear tidal

source of tidal energy

mainly the moon

energy is released by

nuclear fusion in the sun