Chapter 1 - Measurements and Uncertainties Flashcards
Name all the fundamental base units and their symbols
Mass - Kg Length - m Time - s Electric current - A (Ampere) Amount of substance - mol Temperature - K Luminous intensity - cd (Candela)
Name all the SI derived units
Newton - Pascal - Hertz - Joule - Watt - Coulomb - Volt - Ohm - Weber - Tesla - Becquerel -
What are sources of random error?
Readability of the instrument
Observer being less than perfect
The effects of a change in the surroundings
What are sources of systematic errors?
An instrument with zero error or wrongly calibrated
Repeating readings doesn’t reduce systematic errors
What is the difference between accurate and precise errors?
Accurate experiments have small systematic errors ( how close it is to the true value)
Precise experiments have small random errors (how big the spread of data is)
How do you use error bars with a line of best fit and what do error bars show?
The line of best fit must pass through all the rectangles the error bars create. Error bars represent uncertainties.
How do you measure the uncertainties of an analogue scale and what are examples this type if scale?
Rulers and meters with moving pointers are examples
+/- half the smallest division scale
How do you measure the uncertainties of an digital scale and what are examples this type if scale?
Top-pan balances and digital meters are examples.
+/- the smallest division scale
What Significant figures should be used?
Be pessimistic and round to what would be the biggest uncertainty range
What is absolute uncertainty?
It’s the same unit as the quantity being measured
Find the range of the answers and divide by the original.
+/- 🔼 P (P = quantity being measured)
What’s is the fractional and percentage uncertainty?
( +/- 🔼 p ) / p The uncertainty divided by the original amount
(+/- 🔼 p) / p x 100
What is the overall uncertainty if there are 2 or more quantities being divided or multiplied?
The fractional/ percentage uncertainties are ALWAYS added
🔼a = 🔼b + 🔼c
What is the overall uncertainty in an equation that uses powers?
% uncertainty in volume = % uncertainty in [(length)^3]
What is the overall uncertainty if there are 2 or more quantities being added or subtracted?
The overall uncertainty is the addition absolute uncertainties
What’s the difference between a vector and a scalar quantity?
Vectors have both direction and magnitude whereas scalar quantities only have magnitude.
