Just a short, interactive ppt that I made to help anyone taking the P2 gcse exam

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Please be aware that this is a revision guide. It should be used
alongside other activities and revision techniques. Please also
understand that although every effort has been made to ensure that
all subject material has been included, some areas may be
incomplete or missing vital information.
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2. Velocity/Time Graphs
Distance/Time Graphs
Resultant Forces
Acceleration
Work Done
Stopping Distance
Elasticity
More Topics

3. Power
Momentum
Car Safety
Static Electricity
Current and PD
Circuits
Resistance
More Topics
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4. Series/Parallel
Mains Electricity
Atomic Structure
Ionising Radiation
Half Life
Uses of Radioactivity
Radioactive Safety
More Topics
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5. Fission and Fusion
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6. Velocity/Time Graphs
A velocity/time graph plots the speed of an
object against the time it has taken to reach
that speed. The gradient on this graph
represents the acceleration (a positive
gradient means the object is accelerating, a
negative gradient show deceleration and a
flat line shows the object is travelling at a
constant speed)
3m/s/s
Calculate the
acceleration 4m/s/s
of this object.
5m/s/s
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7. Distance/Time Graphs
A Distance/Time Graph shows is similar to
the velocity/time graph however there are
a number of important differences. Firstly,
the gradient on a distance time graph
shows the velocity of the object- If the line
is going up the velocity is positive and vice
versa. Acceleration can also be shown on
a distance/time graph, a line that curves
upwards is accelerating as the distance
covered in a time frame is becoming
greater. A flat line shows a stationary
object and a slope shows a constant
velocity.
It is easy to calculate speed over a section of the graph-:
You must divide the distance covered in that section by the time it has taken the object to travel
that distance. E.g. The first section of the graph: 10/6 =1.66
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8. Resultant Forces
The Resultant force
is the sum of all
forces acting upon The resultant force acting on the truck is
an object 40N. 100N+-60N. The 60N becomes a
minus force is it is acting against the
major force or the force that is moving
the object in the desired direction.
If the resultant force is The up thrust
zero then the forces are balances the
balanced and the object is weight of the
stationary. boat
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9. Acceleration
A positive resultant force is required to get an Resultant Force
object to begin accelerating. An acceleration (newtons)=
however is not just a change in speed, it can take
5 forms- mass(kg)
-Starting x
-Speeding up acceleration(m/s/s)
-Slowing Down (deceleration)
-Stopping
-Changing Direction
When two objects
interact, the
On a force diagram the arrows will always be forces they exert
unequal if an acceleration is occurring. on each other are
equal and
Acceleration can also be represented on a opposite.
distance/time graph and a velocity/time graph.
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10. Work Done
When a force moves an object through a distance, energy is transferred and work is done.
In essence, work done is the amount of energy that has been used to move an object a distance.
Gravitational potential energy works by a similar principle. When an object is raised, work is done to
fight the force of gravity, this energy is transferred to gravitational potential energy in the object
which become kinetic when released. The formula below is effectively calculating the work done in
lifting the object.
GPE(J)=Mass x Gravity x Height
Work Done(J)= Force(N) x Distance(m)
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11. Stopping Distance Start/Replay
Brakes Applied
!
Thinking Distance
Braking Distance
Thinking Distances
Braking distances can
can be affected by-
be Click here
affected by-
Driver notices other car Drugs, alcohol
Damaged Brakes, Icy
tiredness and other
Roads and Worn Tires
distractions.
Stopping Distance=Thinking+Braking
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12. Elasticity
Hooke's law stated that the extension of an elastic
object is directly proportional to the force that is
Elastic objects can store applied to it. Therefore the force applied can be
energy from work done to calculated using the formula.
them as elastic potential
energy. Force(N)= Spring Constant (N/m) x Extension(m)
When a force is removed The spring constant is a measure of how how
from an elastic object it elastic the object is.
quickly transfers to kinetic
energy. However there is more to Hooke's law, the
previous only applies up until a certain point.
When enough force is applied, the object reaches
its limit of proportionality, and the force required
to stretch the spring a certain distance, stops
increasing. If the object is stretched beyond the
limit of proportionality then it is no longer elastic
and will not return to its original shape.
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13. Power
Power is the rate at which work is done-i.e how
much energy is transferred per second whilst
Power is measured
exerting force on an object. in watts (W) or
joules per second
(j/s)
Power(W)= Work Done(J)/Time Taken (s)
So…If a motor does 4.8 kJ of work in 2 minutes
then its power output is 40 watts (4800/120)
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14. Momentum
Momentum(kg m/s) = Mass (kg) x Velocity (m/s)
Momentum is a concept that occurs in The law of conservation of momentum
moving objects. The greater the mass of an states that the total momentum before an
object and the greater its velocity, the event is equal to the total momentum after
greater the momentum. Forces can effect the event. For example in the diagram
momentum, if a positive force is apllied to below, the yellow brick had a negative
an object then the momentum, along with momentum and the blue a much greater
the acceleration will increase. Likewise, if a positive momentum. Therefore when they
negative force is applied then the objects collide they move in a positive direction.
momentum will decrease. Resultant Momentum.
A Newtons
cradle
demonstrates
the law of
conservation of
momentum
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15. Car Safety Cars also make use of the concept of
power. Different cars will have a different
power rating depending on the time it
takes them to do a certain amount of
If a vehicle is involved in a collision then
work. In most cases, however, it is
there is a sudden change in momentum,
important for a car to have a low power
velocity and acceleration. During this
rating, as it will use a smaller amount of
event most of the laws discussed in this
energy in a time period and is often then
topic (red) are applied.
cheaper to run. Sports and performance
cars require a larger engine which will
Safety features such as airbags and
produce a greater power output,
seatbelts aim to reduce the effect that
henceforth the vehicle will be less
these factors have on the human body.
economical but able to do more work in a
When a vehicle slows suddenly, during a
time frame.
collision a large amount of kinetic energy
is transferred into the cabin. Cars are
designed to convert the energy from the
accident in the safest way possible. They
often do this by using crumple zones
which increase the time in which the
change in momentum happens, therefore
reducing the force on the occupants.
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16. Static Electricity Static electricity is a build up of electrons on an
insulating material. When tow insulating materials
rub together, negative electrons collect on one of
the materials, this leaves an absence of electrons
on the other material and therefore a positive
charge.
Static charges are notated as follows:
+ve shows a positive static charge (lack of
electrons)
-ve shows a negative static charge (build-up of
electrons)
When a static charge is near to a conductor, the
electrons can jump to the conductor, often there is
a spark as this occurs. As shown in the image
(opposite) the negative electrons on the child's hair
are repelling each other, causing the hair to pull
away from all the other negatively charged strands
of hair.
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17. Current and Potential
Difference
Current is the flow of electrons around
a circuit, the current will only flow of
there is a potential difference across a
Potential difference is the change in component as it is attracted to the less
energy either side of a component. negative area. Unit- Ampere (A)
This is caused by energy being
converted when the component does
work. Cells create a potential
difference to encourage a current to Charge is a measure of the amount of
flow around the circuit. current passing through a circuit in a
given time. Charge is therefore a
measure of how powerful the electron
is, it is a measure of how strong its
P.D (v) = Work Done(j)/ Charge(C) (negative) charge is.
Current (A)= Charge(C)/Time(s)
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18. Circuit Components
A diode is often made from a semi-conductor material such as silicon,
it is used to regulate the potential difference within a circuit. It does
this by only allowing the current to flow in one direction through the
component.
An LED is emits light when a current flow through it in a forward
direction. LED’s are far more efficient than normal lights and are
becoming more and more popular for use in the home.
A LDR (light dependant resistor) alters its resistance depending in the
amount of light that it is detecting in the environment around it. In a
bright light the resistance is less and vice versa. These have lots of
uses such as in outdoor lighting and burglar alarms.
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19. Resistance
The diagrams below plot the current against
the potential difference. In a resistor the
resistance is constant as it allows the current
A resistor is a component in a only to increase proportionally to the
circuit that controls the amount potential difference. On the other hand, the
of current flowing through a filament lamp increases in resistance as the
circuit. When a current passes filament heats up, as this cools (explained
through a resistor, some of the left) the resistance decreases again.
electrical energy is converted to The steeper the line on these graphs the
heat energy. As the resistor heats greater the resistance.
up, the resistance increases
therefore decreasing the currant
and the heat.
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20. Series/Parellel
In a parallel circuit, each
In a series circuit, the different
component is separately connected
components are connected in a
to the power supply of in its own
line, end to end, between the two
‘loop of the circuit. Therefore is
ends of the power supply. If one of
one component is removed from
the components breaks or is
the circuit then it will have little or
removed then the circuit is broken
no effect on the other components
and power will be lost to all
in the circuit. Although the current
components.
is still shared around the whole
circuit, the potential difference is
Also the potential difference is
the same in all of the components.
shared across all components in
This means that there is very little
the circuit so bulbs will be dim,
change in the output of
motors slow , buzzers quiet etc.
components as more components
Also in a series circuit the
are added. Ammeters are always
resistance of one component has
connected in series even in a
an effect on all parts of the circuit.
parallel circuit.
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21. Mains Electricity
An oscilloscope trace shows if a
current is AC or DC . If the line on
the display is flat then the current is
constant or direct. If there is a wave
Mains electricity is an AC supply at 230
pattern then the current is
volts. This means that the current is
alternating.
constantly changing direction. A battery
or cell produces a direct current which is
Using this display one can calculate
a constant flow of electrons.
the frequency of the electricity
supply.
Frequency (Hz) = 1/Time Period (s)
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22. Atomic Structure
Around 100 years ago, scientists
An atom is made up of two main parts. There
believed that the atom was a ball of
is a nucleus made up of neutrons (no charge)
positive matter with small negative
and protons (positive). Electrons (negative)
matters inside. This was known as the
then orbit the nucleus in rings. There is always
plum pudding theory. In 1909
the same number of electrons as there are
Rutherford and Marsden completed
protons, therefore if there is an imbalance
an experiment that concluded that
then the atom gains a charge. Different
the plum pudding was wrong, they
elements have different numbers of electrons
then devised their own theory, which
protons and neutrons.
is the one that we go by today.
Particle Mass Charge
Proton 1 +1
Neutron 1 0
Electron 1/2000 -1
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23. Ionising Radiation
Type of Decay What is it? When is it Image
released?
Beta Particles A high energy When a neutron
electron splits into a
proton and a
electron
Alpha Particles 2 protons and 2 Lost from
neutrons isotopes
Gamma Particles Pure energy When atoms is
released from too heavy and
nucleus must release
energy.
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24. Half Life
A Half-Life is the average time it takes for the
number of nuclei in a radioactive isotope sample to
halve. The decay of a sample is measured by the
count rate, that is the number of radioactive
particles released from a sample containing the A Geiger counter detects the
isotope in a given time. radioactive particles released
from a sample
As shown in the previous topic, radioactive samples release radioactive particles. We
use the concept of a half life to show how quickly a sample is decaying. A half life is
the time it takes for half thee unstable nuclei in a sample to decay. It is necessary to
quote a half life rather than a ‘full decay life’ as the radioactive release slows over
time. For example when half of the original sample had decayed, the rate of decay is
now half as fast as it was before. This means that a sample will never stop decaying
as it is forever slowing its decay.
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25. Uses of Radioactivity
Gamma rays are also often
Smoke Detectors use alpha radiation to help detect smoke.
used to sterilise food and
Inside there is a weak source of radioactive radiation is
surgical instruments. In
placed near two electrodes, the source causes ionisation
both of these
and allows a small current to flow. If there is a fire then the
circumstances, high doses
smoke absorbs the radiation and causes the circuit to
of gamma waves are
break, resulting in an alarm sounding
targeted at the object, they
then kill most microbes on
the surface of the object.
Medical professionals use gamma radiation to treat This is much more efficient
cancers during radiotherapy. They use high doses of than conventionally boiling
gamma radiation, target at the cancerous cells, this results the object, as the gamma
in the cells being destroyed and often the cancer killed. rays do not damage nor
There are however many risks to radio therapy as the leave a lasting effect on the
targeting of the radiation is not always correct and some object accept for the
healthy cells are killed, sometimes resulting in long term desired removal of
damage. microbes.
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26. Radioactive Safety
There are a number of precautions that
Alpha, Beta and gamma radiation can
need to be made when near a radioactive
enter living cells and collide with other
source.
matter, this causes ionisation which can
damage of destroy living matter. If the
1. Never allow skin contact with the
radiation does not destroy the cell then it
source, where gloves or use tongs.
is likely to cause it to mutate, it will
2. Minimise the time that you are near
multiply uncontrollably, these cells are
the source as this will reduce the
cancerous.
amount of radiation that reaches you.
3. Don’t look at the source as eyes are
Beta and gamma radiations are most
particularly susceptible to damage.
dangerous to humans as it can penetrate
4. Store radioactive samples in a lead
the skin and cause damage to delicate
lined box, lead is one of the only
internal organs . Alpha particles are far
substances to absorb all three kinds of
more ionising and one inside the body
radiation. People who work around
(perhaps through ingestion) then they can
radiation often wear lead-lined
cause catastrophic damage.
aprons.
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27. Fission and Fusion
Nuclear power stations use nuclear fission to generate Nuclear fission releases
electricity. During this process, a large amount of heat more energy than fusion
energy is released, this is used to heat water and turn however it is far more
a turbine, as in a conventional power station. difficult to do on earth.
Fusion is the opposite to
For nuclear fission to occur, a neutron is fired at the fission in that the two
nucleus of a uranium atom this causes the nucleus to smaller nuclei are forced
split to form two smaller nuclei, this process release a together to form a larger
great amount of energy. one. This can only occur at
around 10000000 degrees
The main problem with this process is that the waste centigrade so is therefore
produced (the two new nuclei ) is highly radioactive only currently occurring in
and therefore difficult to dispose of. the sun. Although it is
possible to complete fusion
The heat energy released is often so great that it is on earth, the energy
difficult to control, there have been a number of currently required to reach
disasters in recent years where operators have lost that temperature is greater
control of the reactor and great damage has been than the harvestable energy
done. produced.
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