Units measurements and error Flashcards
What are the SI base units
kg, m, s, A, K, mol
How can you ensure a metre rule is held vertically?
Use a plumb line, set square or spirit level
How do you avoid parallax error?
Ensure eye, object and scale are all in line with each other OR ensure object and scale are directly adjacent to each other
What is meant by the resolution of a measuring instrument?
The smallest change in quantity that can be measured.
What is the resolution of a ruler
1 mm
What is the resolution of vernier calipers?
0.1mm
What is the resolution of a micrometer
0.01mm
How do you find the absolute uncertainty from repeated readings?
± ½ the range of the repeats
What do you do to the uncertainties when quantities are added or subtracted?
The absolute uncertainties are added together
How do find the absolute uncertainty of a single measurement?
± the resolution of the instrument
How do you calculate percentage uncertainty?
(Absolute uncertainty ÷ ‘calculated OR measured’ value) × 100
What do you do to the uncertainties when quantities are multiplied or divided?
The percentage uncertainties are added together
What do you do to the uncertainties when a quantity is raised to a power?
The percentage uncertainty is multiplied by that power
How do you find the uncertainty in a gradient?
± (gradient of the line of best fit − gradient of the line of worst fit)
What is a line of worst fit?
The steepest or shallowest line that passes through the error bars.
