**NOT A SUMMARY, THIS IS IN COMPLETE DETAIL**
I attained 99 in Combined Science solely through this self made resource of mine. I have painstakingly gathered information from every EDEXCEL specific resource I could lay my hands on (including seneca, pmt, savemyexams, lit every single video on each...
PHYSICS PAPER 2:
**NOT A SUMMARY, THIS IS IN COMPLETE DETAIL**
I attained 99 in Combined Science solely through this self made resource of mine. I have painstakingly
gathered information from every EDEXCEL specific resource I could lay my hands on (including seneca,
pmt, savemyexams, lit every single video on each topic i could find and the EDEXCEL textbook itself) in
order to create this incredibly precise document. It meets every single specification point in meticulous
detail, including diagrams and lengthy explanations where needed. It is the boiling pot of absolutely every
single thing you need to know, nothing more nothing less, to seize your 99 in GCSE Combined Science.
→ (Specifically with physics, as most kids find this to be the most challenging, i’ve included an
array of questions after each topic concludes.)
Key:
Boldened: Specification point itself.
Unit 8: Energy – forces doing work
(This unit has many exact spec points as Unit 3 in Paper 1)
8.1 Describe the changes involved in the way energy is stored when systems change
An object projected upwards or up a slope:
● The object's energy is initially in the kinetic store as it moves upwards.
● The object's energy is slowly transferred from the kinetic store to the gravitational potential store as it slows
down and climbs higher.
● Once the object reaches its highest point, all of it's energy is in the gravitational potential store.
● As the object falls again, energy transfers from the gravitational potential store to the kinetic store.
A moving object hitting an obstacle:
The object's energy is in the kinetic store to begin with because it is moving.
● When the object collides with the obstacle, energy is converted to:
● The kinetic store of the obstacle (making it move),
● The thermal store of the object and the obstacle (the particles in the object and the obstacle vibrate
more).
● Some energy remains in the object's kinetic store as it moves away after the collision.
An example would be you throwing a bowling ball and hitting a pin:
● As you move the muscles of your arm to throw the ball the chemical energy store in your muscles decreases
and the kinetic energy store of the bowling ball increases.
As the ball hits a pin, some of the kinetic energy has been transferred to a store of thermal energy, causing
the ball and its surroundings to warm up a little (rise in temp)
You will also hear a sound when the ball hits the pin, the energy of the sound is also transferred to the
internal (thermal) energy store of the surroundings
An object being accelerated by a constant force:
● Work is done by a force on an object.
● This work is converted to the object's kinetic store.
● For example, a bowling ball being dropped off a sky scraper
At its highest point, the ball has a store of GPE, and as it is dropped the gravity does work on the ball
(assuming there's no air resistance), causing the ball to accelerate constantly towards the ground. Just
before the ball hits the ground, it has a store of kinetic energy.
A vehicle slowing down:
, ● To begin with, the vehicle's energy is in the kinetic store.
● The brakes do work, slowing the car down. During this process, energy is dissipated (lost) through heat and
sound.
● For example, when you apply the brakes in a lorry
The moving lorry has a store of kinetic energy. As the brakes are applied, the kinetic energy decreases. The
energy is transferred to the internal energy store in the brakes and the brakes get hot.
You will hear a sound when the brakes of the lorry are applied; the energy of the sound is also transferred to
the internal energy store of the surroundings. When the lorry stops its kinetic energy store is zero.
Bringing water to boil in an electric kettle:
● Energy transfers from the electrical store of the mains power supply to the thermal store of the water,
increasing its thermal store therefore increase in temperature and as bubbles form the kinetic energy store
of the water increases.
Turning on an electric shaver:
- The battery has a store of chemical energy. The current flows through an electrical pathway to the
motor. Energy from the motor follows a mechanical pathway to a kinetic store of the moving blades, a
heat pathway to a thermal store and a radiation pathway to a sound store.
Kinetic energy: Moving objects have their energy in their kinetic store
Gravitational: Objects gain energy in their gravitational potential store when they are lifted above ground
Elastic: Objects have energy in their elastic potential store if they are stretched
Electrostatic: Objects with charge like electrons and protons interacting with one another have energy in
their electrostatic store
Chemical energy: Objects with energy in their chemical store can release energy in chemical reactions
Nuclear: Atomic nuclei release energy from their nuclear store during nuclear reactions
Thermal: All objects have energy in their thermal store, the hotter the object the more energy it has in
thermal store.
8.2 Draw and interpret diagrams to represent energy transfers (3.3)
Sankey diagrams are used to represent energy transfers. The arrow pointing to the right ends up as the desired store
- the useful energy output. The arrow that points down represents the wasted energy. The width of each arrow is
proportional to the amount of energy going into each store.
As a result of the conservation of energy: Total energy = useful energy out + wasted energy
,8.3 Explain that where there are energy transfers in a closed system there is no net change to the total
energy in that system (3.6)
In physics, a system is defined as: An object or groups of objects.
In a closed energy system, there can be transfer of energy but not mass. There is no net change to the total energy in
the system. This is because energy can be accounted for even when the energy stores change within the system and
due to the LAW OF CONSERVATION OF ENERGY stating:
Energy cannot be created, nor destroyed so:
total energy in = total energy out, THEREFORE, the total energy supplied must always equal the total energy
transferred in a system.
8.4 Identify the different ways that the energy of a system can be changed
a through work done by forces
b in electrical equipment
c in heating
Transfer pathways:
Mechanical work/work done > When a force causes an object to move through a distance, WORK IS
DONE on the object, So a force does work on an object when the force causes a displacement
(movement from its original position) of the object.
+ Since Work causes an object to move, work is done against frictional forces, causing the object’s
temperature to rise. Energy is also dissipated by heating to the thermal store of the surroundings. For
example, a person warms up their hands by repeatedly rubbing them together. Another example would
be a person pushing a box, where energy would be transferred mechanically from the kinetic store of the
person to the kinetic store of the box.
- At the same time, energy is transferred by heating from the kinetic store of the box to the thermal store
of the floor (due to friction) and by heating to the thermal store of the surroundings as the sound waves
transfer energy away from the system and cause the air particles to vibrate.
Electricity > In electrical equipment, a charge (flow of charge) moving through a potential difference.
+ Work is done when current flows to operate electrical equipment. A current flows when there is a
potential difference applied to the circuit. This is provided by the power supply or a cell.
Energy is transferred electrically from the power supply to the components in the circuit -> This is the
electrical work done by the power supply when a current flows.
Energy from the chemical store of the cell is transferred electrically to the thermal store of the lamp as
the filament heats up. Energy is transferred from the thermal store of the lamp by heating and by
radiation to the thermal store of the surroundings. Energy is also transferred by heating to the thermal
store of the wires due to resistance.
Heating (NOT thermal) > In heating, energy is transferred from a hotter object to a colder one:
+ Energy transfers by heating increases the energy in the thermal store of the particles that make up
that system which either raises the system’s temperature or produces a change in state. For example:
WARMING A PAN ON THE HOB -> Energy is transferred electrically from the main supply to the thermal
store of the hob which is then transferred by heating to the thermal store of the pan
8.5 Describe how to measure the work done by a force and understand that energy transferred (joule,
J) is equal to work done (joule, J)
, Energy transferred in joules is the same amount as work done in joules.
8.6 Recall and use the equation:
8.7 Describe and calculate the changes in energy involved when a system is changed by work done by
forces
Use work done equation:
Work done = force x distance
Whenever any work is done, energy gets transferred (mechanically) from one store to another. The
amount of energy transferred (in joules) is equal to the work done (also in joules)
if a force acts in the direction that an object is moving, then the object will GAIN energy (usually in the
form of kinetic energy).
If a force acts in the opposite direction to the movement, then the object will LOSE energy (usually as
heat)
if a force is applied to an object, but doesn't result in any movement, NO WORK HAS BEEN DONE.
Example: A car moving at speed beings to apply the brakes. The brakes of the car apply a force of 500N
which brings it to a stop after 23m. Calculate the work done by the brakes in stopping the car.
Distance = 23m
Force = 500N
so 23 x 500 = 11, 500 J
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