# PHYSICS UNIT 2 NOTES

Here are my notes for Physics Unit 2 - if i need to make any corrections or I'm missing something - please tell me

But anyways, hope this will help

Good Luck!

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• Created by: Bessem
• Created on: 05-04-13 18:54

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PHYSICS UNIT 2 NOTES
Physics
RESULTANT FORCES
Forces work in pairs
The Resultant force is simply what you get when you add forces together
But you can only add forces which are opposite each other
Find the resultant force by finding the difference, of the numbers if they are opposite sides
and the arrow goes on the bigger force
If there is NO resultant force (zero) we can say that the forces are balanced
If there IS a resultant force (non-zero) we can say that the forces are unbalanced
FORCES AND MOTION
FORCES AND BRAKING
Stopping Distance = Thinking Distance + Braking Distance
Stopping Distance = the distance the car moves after you have decided to stop it
Thinking Distance = the distance the car moves while the driver thinks about stopping
(approx only a fraction of a second but the car still moves)
Braking Distance = the distance the car moves whilst the driver has their foot on the brakes
FACTORS AFFECTING THE THINKING DISTANCE:
Tiredness
Mobile Phones
Drugs
Alcohol
Distractions
Car's Speed
FACTOR'S AFFECTING THE BRAKING DISTANCE:
Snow
Ice
Wet Weather
Sleet
Wore down tires (Poorly maintained car)
Car's Speed
FALLING OBJECTS

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PHYSICS UNIT 2 NOTES
Mass = a measure of how much stuff you are made up of (kg)
Weight = mass x gravitational field strength W=mg (N) = kg x (N/kg)
Earth's gravity = 10
Space's gravity = 0 (WEIGHTLESS)

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PHYSICS UNIT 2 NOTES
KE increases with greater mass and greater speed
KE= ½ x mass x speed2
When the height is zero there is no GPE, the KE is at a maximum
MOMENTUM
Momentum is a useful quantity to consider when thinking about `unstoppability'
Momentum (kg/s) = mass (kg) x velocity (m/s)
P=mv
Momentum has both magnitude and direction
CALCULATING MOMENTUM
When calculating momentum when there are two speeds in opposite directions ­ make
one speed negative and the other positive.…read more

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PHYSICS UNIT 2 NOTES
If you rub two insulating materials together, electrons will transfer from one to another
One will become positively charged (the one with that lost electrons), the other will
become negatively charged (the one that gained electrons)
If something is neutral (not charged e.g. water) then it becomes attracted to a material
which is charged due to static electricity
Rubbing a POLYETHENE ROD with a dry cloth transfers electrons to the surface atoms of
the rod from the cloth.…read more

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PHYSICS UNIT 2 NOTES
The size of an electric current (I) = The number of electrons flowing (Q) / through a
component per second (t)
I = Q/t
Where
o I = Current in Amps
o Q = Charge in Coulombs
o t = Time
Words Symbols Units
Current I Amps (A)
Time t Seconds (s)
Charge Q Coulombs (C)
The current flows from the positive side of the cell around the
circuit
The electrons flows from the negative side of the cell because

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PHYSICS UNIT 2 NOTES
The current through a resistance at a constant temperature is directly proportional to
the proportional difference (voltage) across the resistor.…read more

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PHYSICS UNIT 2 NOTES
If you remove or disconnect one component, the circuit is broken and everything in the
circuit stops. (This is why most Christmas lights are now connected in parallel circuits,
because if one bulb goes out they all go out.…read more

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PHYSICS UNIT 2 NOTES
An AC = the current flows in one direction then back in the direction where it came from
(it is constantly changing direction back and forth)
A DC = the current flows in the same direction
The UK Mains supply an ALTERNATING CURRENT
Cells & Batteries supply DIRECT CURRENT
Oscilloscope (Voltmeter)
When you plug in a DC supply in an oscilloscope, the trace is just a straight line (A DC always
has the same voltage)
When you plug in an AC…read more

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PHYSICS UNIT 2 NOTES
1
F requency (Hz) = Time Period (s)
The time period is the time it takes to make a complete wave (from peak to peak)
To find the time period measure the horizontal distance between the two peaks using the
divisions (the squares on the x axis of diagram) then using the squares on the x axis, each
square is an amount of seconds the amount of squares between peak to peak X the seconds
each square is worth = time…read more

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PHYSICS UNIT 2 NOTES
FUSES
We want an appliance which will blow if the current is too much ­ reason for fuse
Fuse protects the appliance so we know when the appliance is getting damaged
If the fuse rating is too high for the appliance it is letting the appliance get damaged
Earth wire protects us from getting electrocuted
If an appliance overheats ­ too much current is passing through ­ it could cause a fire
A fuse contains a thin wire that heats up,…read more