Workbook 1 - Measurements and Their Errors Flashcards
What are S.I. units?
A coherent system of units that all fit together. When doing calculations you need to convert measurements in S.I. units.
What are the 7 fundamental S.I. units?
- Ampere (A), the unit of electrical current
- Candela (cd), the unit of luminous intensity
- Kelvin (K), the unit of temperature
- Kilogram (Kg), the unit of mass
- Metre (m), the unit of length
- Mole (mol), the unit of quantity of a substance (how many atoms or molecules)
- Second (s), the unit of time
Other important S.I. units?
Speed - ms^-1 Area - m^2 Volume - m^3 Force (Newtons) - N or kgms^-2 Energy (Joules) - J or kgm^2s^-2
What are the 10 prefixes?
- Tera - T - 10^12
- Giga - G - 10^9
- Mega - M - 10^6
- Kilo - k - 10^3
- Centi - c - 10^-2
- Milli - m - 10^-3
- Micro - mu - 10^-6
- Nano - n - 10^-9
- Pico - p - 10^-12
- Femto - f - 10^-15
Definition of accuracy?
A measurement result is considered accurate if it is judged to be close to the true value
What is calibration?
Marking a scale on a measuring instrument. This involves establishing the relationship between indications of a measuring instrument and standard or reference quantity values, which must be applied. For example, placing a thermometer in melting ice to see whether it reads 0 degrees, in order to see if it has been calibrated correctly
What is data?
Information, either qualitative or quantitative, that has been collected
What is measurement error?
The difference between a measured value and the true value
What are anomalies?
These are values in a set of results which are judged not to be part of the variation caused by random uncertainty
What is random error?
These cause readings to be spread about the true value, due to results varying in an unpredictable way from one measurement to the next. The effect of random errors can be reduced by taking more measurements and calculating a mean.
What is systematic error?
These cause readings to differ from the true value by a consistent amount each time a measurement is made.
Zero error?
An indication that equipment gives a false zero reading
What is evidence?
Data which has been shown to be valid
What is a fair test?
A test in which only the independent variable has been allowed to affect the dependent variable
What is a hypothesis?
A proposal intended to explain certain facts or observations
What is interval?
The quantity between readings
What is precision?
Precise measurements are ones in which there is very little spread about the mean value. It depends only on the extent of random errors
What is a prediction?
A prediction is a statement suggesting what will happen in the future, based on observations, experience or a hypothesis
What is the range?
The maximum and minimum values of the independent or dependent variables. It is important in ensuring that any pattern is detected
When are measurements repeatable?
If the original experiment repeats the investigation using the same method and equipment and obtains the same results.
When is a measurement reproducible?
If the investigation is repeated by another person or by using different equipment or techniques and the same results are obtained
What is resolution?
This is the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the reading
What is a sketch graph?
A line graph that generally shows the shape and relationship between two variables. Doesn’t have any points plotted but does need labeled axes
What is the true value?
The value that would be obtained in an ideal measurement
What is uncertainty?
The interval within which the true value can be expected to lie, with a given level of confidence or probability
What is validity?
Suitability of the investigation procedure to answer the question being asked
What is a valid conclusion?
A conclusion supported by valid data, obtained from an appropriate experimental design and based on sound reasoning
What are categoric variables?
Values that are labels
What are continuous variables
Continuous variables can have values that can be given a magnitude either by counting or by measurement
What are control variables?
A control variable is one which may, in addition to the independent variable, affect the outcome of the investigation and therefore has to be kept constant or at least monitored
What are dependent variables?
A variable of which the value is measured for each and every change in the independent variable
What are independent variables?
Variable for which values are changed or selected by the investigator
How do you read a micrometer?
The scale on the sleeve is in millimeters, the scale on the thimble is in 1/100ths of a mm. 1 full rotation is 0.5mm
How do you calculate the percentage error of T=2.0s +/- 0.1s?
0.1/0.2 x 100
What is the equation that can be given for a simple pendulum?
T = 2pi x square root (l/g)
What is the equation for percentage error?
Percentage error = error/true value x 100
Error = measured value-true value
What is Hooke’s Law?
Extension from the natural length is proportional to the force applied up until the limit of proportionality
Why is an estimate not just a guess?
Because it is the result of a calculation where some of the data used is based on typical values
