Measurements Flashcards
Define physical quantities
Physical quantities are quantities that can be measured
What are the 7 base quantities and their base units
- Length / m
- Mass / kg
- Time / s
- Current / A
- Temperature / K
- Amt of substance / mol
- Luminous intensity / cd
Define homogeneous equation
A homogeneous equation is one where the base units of each term are the same
What are random errors
- Different magnitudes and signs when measurements are repeated
- Unpredictable
- Can be reduced by taking average
- Cannot be eliminated
What are systemic errors
- Same magnitude and sign when measurements are repeated
- Cannot be eliminated by averaging
- Eliminate by careful experiment design
Define accuracy
Accuracy is how close a measured value or average of repeated measured values is to the true value
Define precision
Precision is how close the repeated measured values are to each other, regardless of true value
How are accuracy and precision related to different errors
- Systemic errors affect accuracy
- Random errors affect precision
Define uncertainty
Uncertainty is the total range of values within which the measurement is likely to lie in
How to get percentage uncertainty
Fractional uncertainty x 100%
For formula method, when to use actual uncertainty
Addition and subtraction
For formula method, when to use fractional uncertainty
Multiplication and division in index form
Define scalar quantity
A scalar quantity is a physical quantity with magnitude only
What is a change in vector A equal to
A(change) = A(final) - A(initial)
Define vector quantity
A vector quantity is a physical quantity with both magnitude and direction
What does it mean for something to be dimensionless
No units
