p3 & p4 revision

8/2/2019 p3 & p4 Revision

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Interpret the relationship between speed, distance and time including: increasing the speed, which increases the distance travelled in the same time. increasing the speed reduces the time needed to cover the same distance. the eff ect of changing any one or two of the quantities.

Explain that acceleration could involve either a change: in speed; in direction.Interpret the relationship between acceleration, change of speed andtime to include the eff ect of changing any one or two of thequantities.


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Often get questions along the lines of, if vdoubles what happens to the kinetic energy?

(quadruples because of the v2 bit)

Describe and explain that car fuel consumption gures depend on:energy required to increase KE;energy required to do work against friction;diff erent driving styles and speeds;diff erent road conditions.

Explain that electrically powered cars do not pollute at the point of use whereas fossil fuel cars do.Recognise that battery driven cars need to have the battery recharged:

this uses electricity produced from a power station;power stations cause pollution.

Describe how seatbelts, crumple zones, air bags are useful in a crashbecause they:

change shape; reduce injuries; absorb energy.

Describe how typical active safety features can make driving safer.

Describe how typical passive safety features can make driving safer

Explain that forces can be reduced when stopping (eg. crumple zones,braking distances, escape lanes, crash barriers, seatbelts and air bags) by:

increasing stopping or collision time; increasing stopping or collision distance; decreasing acceleration.

Describe using the ideas of friction why ABS br akes reduce brakingdistances.

Evaluate the eff ectiveness of given safety features in terms of saving lives.


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Terminal velocity Kinetic energy

constant as speedis not changing

Gravitational potentialreducing as object is still

falling

ElectrostaticsDescribe static electricity in terms of the movement of electrons: a positive charge due to lack of electrons; a negative charge due to an excess of electrons.State and recognise that like charges repel and unlike charges attract.State and recognise that electrostatic phenomena are caused by the transfer of electrons.

Ohms lawresistance [] =

voltage [V ]current [A]

Parallel circuit

Series circuit


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Electrical safety Earth wire connected to case

of device and conductselectricity to ground in case of

short circuit

Fuse is a small piece of wire. Too much currentmakes it melt & break thecircuit. is happens in ashort circuit. is protectsthe user. Often packaged

like this

Waves

Frequency is the number of complete cycles in one second. It is

measured in Hetrz. (Hz)

Waves Medical physics

X-ray and gamma;

High energy electromagnetic wave - just like

light

GammaTracers in the body -short half-life needed

Gamma knife - alsoxrays


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X-Ray

Easier to produce thanGamma - similarly

penetrating. Also bad foryou in large doses

Radioactivity

Radioactive glass!

AtomicNumber - how

many protonsand neutrons

ProtonNumber

also = Numberof electrons

e excess energy after an alpha or

beta particle decay isoften emitted as a

wave of electromagnetic

radiation from thenucleus of the atom

and iscalled a gamma ray


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Half-life Background radiation

Some is

natural -some isnt

Uses of radiationtracer -gamma

Sterilise - gamma

Beta

Smoke detector

Radioactive dating


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p3 & p4 revision

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