Measurement Flashcards
What are the base quantities tested in the syllabus?
Mass
time
length
electric current
thermodynamic temperature
amount of substance
Name and symbol of SI Base Quantity:Mass
kilogram,kg
Name and symbol of SI Base Quantity:Time
second,s
Name and symbol of SI Base Quantity:Length
metre,m
Name and symbol of SI Base Quantity:Electric current
ampere,A
Name and symbol of SI Base Quantity:Thermodynamic Temperature
kelvin,K
Name and symbol of SI Base Quantity:Amount of substance
mole,mol
What is the molar mass of carbon-12?
12 grams
How many atoms of carbon does carbon-12 have?
6.02 x 10^23
Name the derived unit and how it is expressed in base units for the physical quantity: Area
m^2,m^2
Name the derived unit and how it is expressed in base units for the physical quantity: Force
N, kg m s^-2
Name the derived unit and how it is expressed in base units for the physical quantity: Energy
J, kg m^2 s^-2
Express the unit for charge Q in terms of the SI base units.
A s
What does a physical equation being homogenous mean?
It means that all terms of the equation must have the same SI bas eunits.
What is a dimensionless quantity?
A dimensionless quantity is a quantity with no unit.
What is a derived unit?
A derived unit is a unit expressed in terms of the product and/or quotient of base units.
Explain why the unit of energy, joules, is said to be a derived unit.
A derived unit is a unit expressed in terms of the product and/or quotient of base units. The unit of energy, joule is said to be a derived unit because it can be expressed in terms of the product and/or quotient of the base units: kilogram,metre and second.
Determine the base units of density p and pressure p.
Density: kg m^-3
Pressure: kg m^-1 s^-2
Considering the unit of c is m s^-1 and that c is a gas,suggest what quantity may be represented by the symbol c.
Since the base units of c is m s^-1, the symbol c may be representing the mean speed of gas molecules
Tell the power and abbreviation of the prefix: deci
10^-1,d
Tell the power and abbreviation of the prefix: centi
10^-2,c
Tell the power and abbreviation of the prefix: milli
10^-3,m
Tell the power and abbreviation of the prefix: micro
10^-6, µ
Tell the power and abbreviation of the prefix: nano
10^-9,n
Tell the power and abbreviation of the prefix: pico
10^-12,p
Tell the power and abbreviation of the prefix: femto
10^-15,f
Tell the power and abbreviation of the prefix: kilo
10^3,k
Tell the power and abbreviation of the prefix: mega
10^6,M
Tell the power and abbreviation of the prefix: giga
10^9,G
Tell the power and abbreviation of the prefix: tera
10^12,T
Tell the power and abbreviation of the prefix: peta
10^15,P
Leave your answers in their basic units and in standard form: Calculate the speed of an electron that travels 50nm in 12µs.
4.2 x 10^-3 m s^-1
Leave your answers in their basic units and in standard form: Calculate the current flowing through a 2.0MΩ resistance with a potential difference of 9.0kV across it.
4.5 x 10^-3 A
Convert 80 cm^2 to m^2.
8.0 x 10^-3 m^2
Convert 6.0 x 10^-4 m^3 to cm^3.
6.0 x 10^2 cm^3
Convert 16 m s^-1 to km h^-1.
57.6 km h^-1
Convert 13.6 g cm^-3 to kg m^-3
13600 kg m^-3
What is the order of magnitude of this quantity: Diameter of atom
10^-10 m
What is the order of magnitude of this quantity: Diameter of nucleus
10^-15 m
What is the order of magnitude of this quantity: Wavelength of visible light(Violet to red)
10^-7 m
What is the order of magnitude of this quantity: Density of water
10^3 kg m^-3
What is the order of magnitude of this quantity: Average speed of a runner
1 m s^-1 or 10 km h^-1
What is the order of magnitude of this quantity: Car speed on an expressway
10 m s^-1,100 km h^-1
What is the order of magnitude of this quantity: Power on a light bulb
10 W
What is the order of magnitude of this quantity: Average electrical power of an iron/air-con
10^3 W
What is the order of magnitude of this quantity: Mass of an average person
10^2 kg
What is the order of magnitude of this quantity: Mass of a car
10^3 kg
What is the order of magnitude of this quantity: Mass of unladen lorry
10^3 kg
What is the order of magnitude of this quantity: Mass of Earth
10^25 kg
What is the order of magnitude of this quantity: Mass of Sun
10^30 kg
Definition of random errors
Random errors are errors of measurements in which the measured quantities deviate from the mean value with varying magnitudes and different signs.
Definition of systematic errors
Systematic errors are errors of measurements in which the measured quantities deviate from the true value by a fixed magnitude and constant sign.
How can you reduce systematic erros?
Systematic errors can be eliminated to obtain the true value of a measured quantity.
How can you reduce random errors?
Random errors can only be minimized(But not eliminated) through various approaches.
An experiment is set up as shown to determine the spring constant of a spring. Using the formula mg=kx, the spring constant k may be determined by finding the extension of the spring,x, and the mass of the load applied,m. Give 1 example of a systematic error and a random error which could occur in this expermient.
Random:
1)Reading from the metre rule taken when the spring system is not stable
2)Parallax error arising from measurement using the metre rule because there is a gap between load and metre rule
Systematic:
1)The ruler may not be vertical.
2)Wrong calibration of electronic mass balance
For each of the following imporvements, state whether it reduces random or systematic error: Take timings for a large number of oscillations(so that the timing exceeds 20 s) to find the period of oscillation
Random error
For each of the following improvements, state whether it reduces random or systematic error: Adjust the instrument to remove its zero error before measurement
Systematic error
For each of the following improvements, state whether it reduces random or systematic error: Measure the diameter of a wire at different positions and calculate its average value.
Random error
For each of the following improvements, state whether it reduces random or systematic error: Determine the zero error in the instrument and account for it by substracting from the measured value
Systematic error
For each of the following improvements, state whether it reduces random or systematic error: Place the pointer of instrument as close to the scale as possible to minimize parallax error.
Random error
For each of the following improvements, state whether it reduces random or systematic error: Use aids such as a plane mirror or a set square when reading a scale to minimze parallax error.
Random error
For each of the following improvements, state whether it reduces random or systematic error: Drawing a graph of best fit from data points collected from the experiment.
Random error
Definition of accuracy
Accuracy is a measure of how close the average of the emasured values is to the true value.
Definition of precision
Precision is a measure of how close each measured value agrees with one another.
With high accuracy, it reduces what errors?
Systematic errors
With high precision, it reduces what errors?
Random errors
Precision of analogue watch and digital watch
Analogue:+-0.01s
Digital:+-1s
How do you determine the mean of 5 values?
Average them
How do you determine the spread of 5 values?
Max value - Min value
Uncertainty in measurement of instrument: Metre rule
1mm
Uncertainty in measurement of instrument: Vernier calipers
0.1mm
Uncertainty in measurement of instrument: Micrometer screw gauge
0.01mm
Uncertainty in measurement of instrument: Digital stopwatch
0.01s
Uncertainty in measurement of instrument: Thermometer
0.5 degrees
Does the actual uncertainty carry a unit?
Yes
Does the fractional uncertainty carry a unit?
No
Does the percentage uncertainty carry a unit?
No
Actual uncertainty is expressed in _ sf
1
Fractional uncertainty is expressed in _ sf
2
Why do we have to calculate fractional and percentage uncertainty?
For smaller objects, there is a higher percentage uncertainty.
Percentage uncertainty is expressed in _ sf
2
When you have your value with an uncertainty, what should you consider on the decimal places?
The decimal places must be the same and must have 1sf for uncertainty.
What is the actual uncertainty of a derived quantity for addition and/or subtraction operation?
The summation of the actual uncertainties of the individual quantities