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Static electricity
What it is?

A charge that is not free to move .This causes charge to
build in one place and it often ends up with a spark
when it moves.

Example of static electricity

Rubbing a rod (polythene and acetate rubbed with cloth)

What causes build up of…

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Dangers

Lightning ­ caused by static charge building in clouds, can damage buildings
Aircraft refuelling build up of charge can cause explosions (ignite fuel)



What causes opposite charges to attract?

Electric force field forces opposite charges to be pulled together.

Direct current = supplied by cells or batteries

Alternating current…

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burglar alarms





Thermistors

hot conditions resistance drops
cool conditions resistance goes up
useful for temperature detectors
E.g. car engine temperature sensors & electrostatic thermostats

Current against pd graphs








Transferring energy

Calculating power




Calculating energy




Speed and velocity
both measured in m/s or mph or km/h
both say how fast you…

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Acceleration & velocity time graphs
Acceleration

How quickly velocity is changing ­ this can be a change in speed or direction
Has size and direction
Vector quantity

Formula

Acceleration = change in velocity / time or acceleration (m/s) = (v-u)/t

Velocity-time graphs




Calculating distance travelled




The steeper the graph the…

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Distance time graphs




Horisontal lines= stationary
Straight sloping lines =constant speed
The steeper the line the fatser the object is travelling
Speed can be calculated using gradient

Forces

The 6 types of forces

Gravity (weight)
Reaction force
Action force
Thrush (push or pull)
Drag
Lift
Tension

Force

Vector quaintly
Measured…

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Action and reaction force




Direction of forces must be taken to account




Newton's first and third law
1st law on motion states that if there is no resultant force then the force acting on the object then:

If stationary , the object will remain at rest
If moving , the…

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If resultant force of an object is not zero then it will continue accelerating in the direction if the resultant force.




Force and acceleration
When resultant force is acting on an object the object will accelerate in the direction of the RF.
Size of acceleration depends on : size of…

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If there us an unbalanced force the object will accelerate in the direction of the force
Overall unbalanced force is called resultant force
Bigger force =greater acceleration
Bigger mass= smaller acceleration




Stopping distance = thinking distance + Braking distance
Thinking distance = distance travelled as driver reacts
Braking distance =…

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The faster the momentum changes the more force on the object
The impact of force on an object can be reduced by increasing the time taken for the object to stop (Impact
time)
In a crash the following are used to reduce the impact force on the driver:
Seatbelts
Crumple…

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KE= energy of movement

KE formula:

KE = ½ mxv2




Conservation of energy

Energy cannot be destroyed or created it can only be transferred into different form.

Braking distance & velocity of a vehicle

KE in a car can be transferred into heat energy by the brakes
In a car…

Comments

Pond

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thank you and God bless **

ManCity81

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good

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