Physical Quantities Part 1 Flashcards
Includes uncertainty
Define physical quantity
Anything that is measurable and can be expressed as a numerical number and unit
What are the 2 types of physical quantities?
Base and Derived quantities
What are the 7 base quantities?
Length - m - metres
Time - s - seconds
Electric current - A - amperes
Mass - kg - kilograms
Temperature - K - Kelvin
Define derived quantity
Quantities that are found by either/both multiplying and/or dividing base quantities
Define accuracy
How close a measurement is to its true value
Define precision
The range within which a measurement’s true value is found
Precision is determined by the scale of the measuring tool
Define Vernier calliper
Measuring tool that can measure small lengths to a fraction of a millimetre
What is the formula for percentage uncertainty?
Absolute uncertainty / Measurement x 100
Define random uncertainty
Happens due to observer
Repeating and taking an average can reduce this uncertainty
Plot a graph
Define systematic uncertainty
Happens due to instrument
Trying different tool / replace tool can reduce this uncertainty
How are uncertainties combined?
Add the fractional uncertainties to get the fractional uncertainties of the quantity that is being measured
Describe the protractor.
Used to measure angles
Divisions are 1 degree apart
Absolute uncertainty of a protractor is 1 degree
Describe the stopwatch
Measures time
A short time interval has a large percentage uncertainty
The absolute uncertainty for time is heavily affected by the reaction time of the experimenter
Describe the CRO (Cathode Ray Oscilloscope)
Used to measure time
Uses a high voltage cathode ray table
To measure the time, the formula Number of periods (T) = Number of divisions x time base setting
