# AQA Physics Unit 2 (P2)

Key facts on the unit 2's specification for Physics!

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• Created by: Triciaaa
• Created on: 05-01-13 12:48

## P2.1 Forces and Their Effects

Resultant forces
When two objects interact, the forces exerted on each other are equal and opposite
Stationary Object: 0 = stationary, non 0 = accelerating
Moving Object: 0 = constant speed, non 0 = accelerating
Forces and motion
F=ma
a=v-u/t
distance travelled = area under graph
Forces and braking
Resistive forces are caused by air resistance
Thinking distance = drugs, alcohol, tiredness
Forces and terminal velocity
w=mxg (m = kg) (w=N) (g=10n/kg)
Forces and elasticity
extension of an elastic object is directly proportional to the force applied (F=ke)

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## P2.2 The kinetic energy of objects speeding up or

Forces and energy
Energy is transferred when work is done
Ep=mxgxh (Ep - j, m - kg, g - n/kg, h - m)

Momentum
conservation of momentum - total momentum before = total momentum after
Safety with momentum = increase in time taken, reduces change in momentum, force exerted on object is less

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## P2.3 Currents in electrical circuits

Static electricity
-negatively charge electrons rub off one material to another
-when two electrically charged objects are brought together, they exert a force on both

Electrical circuits

• Current = flow of electric charge
• Potential difference = energy transferred per coulomb of charge between two points
• Diodes - when a current can only flow in one direction (useful for electronic circuits)
LDR = depends on light intensity, bright = resistance falls, darkness = resisitance increases e.g. night lights, burglar detectors
LED = uses small currents, traffic lights, remote controls
Thermistors =  temperature (hot-resistance drops, cold-resistance goes up)
• Series circuit - current = same, pd = shared, resistance = same
• Parallel circuit - current = shared, pd = same
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## P2.4 Using mains electricity safely and the power

Household electricity

Oscilloscopes: to calculate...
Alternating current
Frequency = 1/t
Amplitude = no. of squares (up) x Ygain unit
Time period =  no. of squares (accross) x time base unit
Direct current
Potential difference = no. of squares (up) x Ygain unit

RCCB (Residual Current Circuit Breakers)
- detect difference in current between the live and neutral wires
- Advantages = faster, sensitive, resettable
- Disadvantages = bigger than a fuse, expensive

CFL's waste less energy as its a power saving lamp

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## P2.5 Radioactive substances decay, uses and danger

- cosmic rays
- rocks
- nuclear accidents and weapon tests
Alpha: 2 neutrons and protons (helium)
- strongly ionising
- doesnt pentrate far
- range in air is small
Beta: electron from nucleus
- moderately ionising
- penetrates moderately
- long range in air
- weakly ionising
- penetrates far into materials
- pass straight through air

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## P2.6 Nuclear fission and fusion

Nuclear Fission: splitting up of big atomic nuclei (usually Uranium235, Plutonium239)
1) absorbs neutron
2) splits into 2 small nuclei, 2/3 neutrons and ENERGY is released
3) starts the chain reaction

Nuclear Fusion: joining of small atomic nuclei
1) two light nuclei (hydrogen) join to produce a larger nucleus (helium)
2) releases LOTS MORE energy than fission (trying to generate worlds electricity)
3) doesnt leave behind radioactive waste

Life cycle of a star

Protostar > Main sequence star > Red giant > White dwarf (then black dwarf)

>  Red super giant > Supernova > Neutron star > Black hole

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This is a really good resource, Thanks :)

But on the first and fifth cards some of the words have been cut off at the bottom, so  I can't read what they say :/

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Thank you! After you told me, I tried sorting it out... its the best I could do to fit all the info in without making it look all unorganised... hahah! I like everything neat so i can think properly but thanks for the input!

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