4 Measurement and Engineering Data Free Online FlashCards

What two parts make up a measurement?

A measurement is a numerical estimate of a quantity expressed as a number and a unit.

What are the seven SI base units?

The seven SI base units are metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd).

How is the newton expressed in SI base units?

A newton is a derived unit of force: $1\,\text{N}=1\,\text{kg}\cdot\text{m}/\text{s}^2$.

What does a conversion factor do?

A conversion factor is a ratio equal to one: it changes the unit without changing the quantity. For example, $1\,\text{in}=25.4\,\text{mm}$.

What are three rules for writing SI unit symbols?

Leave a space between the number and unit symbol. Symbols are case-sensitive and are not pluralized; for example, $\text{m}$ means metre, while $\text{M}$ is the prefix mega.

What do significant figures communicate?

Significant figures show the digits used to express a measured value, but they do not fully describe its uncertainty. For example, $1.200\,\text{km}$ has four significant digits.

How should a product or quotient be rounded?

For multiplication and division, round the result to the number of significant figures in the least precise measured input.

How should a sum or difference be rounded?

For addition and subtraction, round the result to the least precise decimal place among the inputs.

Do exact counts limit significant figures?

Exact counts and defined conversion factors do not limit significant figures. For example, a count of 12 bolts is exact, unlike a ruler measurement.

What does measurement uncertainty describe?

Measurement uncertainty describes the range of values reasonably associated with a measured result. It can arise from instrument resolution, calibration, conditions, procedure, or repeated-reading variation.

How do random and systematic effects differ?

Random effects cause readings to vary; systematic effects, such as a consistent calibration offset, tend to shift readings in one direction.

How do precision and accuracy differ?

Precision concerns the spread of repeated readings; accuracy concerns closeness to an accepted reference value. Readings can be precise yet biased.