Physics 1 - Measurements and Their Errors Flashcards
What are SI units?
Fundamental (base) units of physical quatities.
What is the SI unit of mass?
Kilograms (kg)
What physical quantity is measured in mol?
The amount of a substance.
What is the SI unit of current?
Amperes (A)
Which is SI unit for temperature; °C or K?
Kelvin (K)
This is because kelvin is the absolute scale.
What is the SI unit of length?
Metres (m)
What is the SI unit of time?
Seconds (s)
Are Newtons (N) an SI unit?
No newtons are not fundamental.
What is the SI unit of force?
kilogram meters per second per second, or per second-squared (kgms⁻²)
What is the SI unit of energy?
kilogram meters-squared per second-squared (kgm²s⁻²)
Derive the SI units of energy.
(Kinetic energy) = ½×(mass)×(velocity)
Units=kg×(ms⁻¹)²
=kgm²s⁻²
Derive the SI units of force.
(Force)=(Mass)×(Acceleration)
Units=kg×ms⁻²
=kgms⁻²
What is the prefix -kilo in standard form and what letter/symbol is used to represent it?
×10³
k
What is the prefix -mega in standard form and what letter/symbol is used to represent it?
×10⁶
M
What is the prefix -giga in standard form and what letter/symbol is used to represent it?
×10⁹
G
What is the prefix -tera in standard form and what letter/symbol is used to represent it?
×10¹²
T
What is the prefix -peta in standard form and what letter/symbol is used to represent it?
×10¹⁵
P
What is the prefix -milli in standard form and what letter/symbol is used to represent it?
×10⁻³
m
What is the prefix -micro in standard form and what letter/symbol is used to represent it?
×10⁻⁶
μ
What is the prefix -nano in standard form and what letter/symbol is used to represent it?
×10⁻⁹
n
What is the prefix -pico in standard form and what letter/symbol is used to represent it?
×10⁻¹²
p
What is the prefix -femto in standard form and what letter/symbol is used to represent it?
×10⁻¹⁵
f
What is a random error?
An error that effects precision and cannot be completely removed, it causes differences in measurements.
What is a systematic error?
An error that effects accuracy and occurs because of faults in equipment or experimental method, causing the result to be too large/small by the same amount each time.
What are 3 ways to reduce random error?
Take at least 3 repeats and calculate a mean.
Use a computer or a data logger.
Use higher resolution equipment.
State a cause of parallax error.
Reading a scale at a different angle each time, to correct this you should read scales at eye level to reduce parallax error.
How can systematic error be reduced?
Calibrate apparatus before using it, such as zeroing the balance when it is empty.
Is electronic noise in the circuit of an ammeter random error or systematic error?
It is a random error as it will cause fluctuations in readings that affect precision and it cannot be removed.
Why should background radiation be measured before measuring the radioactivity of a source?
So that the actual radioactivity of the source is measured, rather than both the source and background radiation, by accounting for the amount of background radiation, thus reducing systematic error.
What is precision?
Precise measurements are consistent, they fluctuate slightly about a mean value- precise doesn’t indicate the value is accurate.
What is repeatability?
If the original experimenter can redo the experiment with the same equipment and method, and then get the same result, it is repeatable.
What is reproducibility?
If the experiment is redone by a different person with different techniques and equipment and the same results are found, it is repeatable.
What is meant by resolution?
The smallest change in the quantity being measured that gives a recognisable change in reading.
What is meant if a value is accurate?
The value is close to the true value.
What is absolute uncertainty?
Uncertainty given as a fixed quantity, which, when combined with a reported value, gives a range of values which should contain the true value.
What is percentage uncertainty?
The absolute uncertainty, compared to the reported value, given as a percentage.
What is the formula for percentage uncertainty and what are its units?
(%uncertainty)=((absolute uncertainty)÷(reported value))×100
It has no units, since absolute uncertainty has the same units as the reported value.
What is fractional uncertainty?
The absolute uncertainty, compared to the reported value, given as a fraction.
What is the formula for fractional uncertainty and what are its units?
(fractional uncertainty)=(absolute uncertainty)÷(reported value)
It has no units, since absolute uncertainty has the same units as the reported value.
How can percentage and fractional uncertainty be reduced?
Measure larger quantities, for example, a longer rope will have a smaller percentage uncertainty than a shorter rope
What is the difference between a reading and a measurement?
Readings are when one value is found, measurements are when the difference between two readings are found.
How would you draw a line of best fit on a graph with error bars?
Ensure that the line of best fit passes through all of the error bars.
How would you find the uncertainty in the gradient of a line of best fit?
Draw the steepest or shallowest line of worst fit, it still has to go through all the error bars.
Then calculate the gradient of the lines of best and worst fit, the uncertainty is the difference between their gradients.
How do you work out the uncertainty in the y-intercept of a line of best fit?
Draw a line of best and worst fit. the uncertainty in the y-intercept is:
(best y-intercept)-(worst y-intercept)
What is an order of magnitude?
Powers of ten which describe the size of an object/value, often used to compare different objects/values.
What is the order of magnitude for the diameter of a nucleus?
10⁻¹⁵
What is estimation?
A skill where approximate values are used to make comparisons or to check whether a calculated value is reasonable
