AS Physics - Basics

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  • Created by: dkoning00
  • Created on: 13-04-17 14:09
What are the six base quantities you need to know and their units?
Length - metres; mass - kilograms; time - seconds;current - ampere; temperature interval - kelvin; amount of substance - mole
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What are derived quantities?
Physical quantities defined in terms of two or more base quantities
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Give the derived units of the following:
(Next card)
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Force
Newtons (N)
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Pressure
Pascal (Pa)
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Work/Energy
Joules (J)
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Power
Watts (W)
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Charge
Coulombs (C)
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Potential difference
Volts (V)
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Resistance
Ohms
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List the eight common prefixes from smallest to largest
Pico, nano, micro, milli, kilo, mega, giga and tera
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What is the difference between a vector and a scalar value?
Vector has direction and magnitude, scalar has only magnitude
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Hence describe the difference between distance and displacement
Distance is a measure of how far an object has traveled irrelevant of direction, displacement is a measure of how far the object has moved from its starting point with direction
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Give the six basic vector quantities
Displacement, velocity, acceleration, momentum, force and moment
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How would you resolve a one dimensional force, F, perpendicularly?
Vertical component = Fsin(angle) Horizontal component = Fcos(angle)
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What is an error?
The difference between a measured value and the true value
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What is an uncertainty?
An error of unknown size
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Describe accuracy
A measured value is considered accurate if it is deemed to be close to the true value. Accuracy cannot be quantified and is affected by random and systematic errors
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Describe precision
Precision denotes the consistency obtained between values obtained by repeated measures i.e. clustered values are precise. Precision is only affected by random errors and can be quantified (e.g. standard deviation)
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How can you increase the accuracy of an experiment?
Reduce systematic errors - take sensible precautions, avoid parallax and zero errors, use instruments with reasonable resolution
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How can you increase the precision of an experiment?
Reduce ransom errors - repeat experiments several times being careful not to change any parameters, identify and remove outliers from data, plot a line of best fit to average values
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What is the best way to express accuracy of an experiment?
By expressing uncertainties as percentages
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How do you do this?
By determining the resolution of the equipment and the proportional error this incurs on the result - a resolution of +/-1mm on a metre rule is an uncertainty of 0.1%
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How do you compound errors in calculations?
Turn every uncertainty into a percentage and add all of them appropriately for the equation (multiply uncertainties by the index)
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Other cards in this set

Card 2

Front

What are derived quantities?

Back

Physical quantities defined in terms of two or more base quantities

Card 3

Front

Give the derived units of the following:

Back

Preview of the front of card 3

Card 4

Front

Force

Back

Preview of the front of card 4

Card 5

Front

Pressure

Back

Preview of the front of card 5
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