Expressing Quantities & SI Units Flashcards

All 14 cards in this deck

Give the SI units of mass, force, energy and frequency.

Mass: kilogram (kg); force: newton (N); energy: joule (J); frequency: hertz (Hz).

What do the prefixes giga (G), mega (M) and kilo (k) multiply a unit by?

giga = $\times 10^{9}$, mega = $\times 10^{6}$, kilo = $\times 10^{3}$.

What do the prefixes centi (c), milli (m), micro (μ) and nano (n) multiply a unit by?

centi = $\times 10^{-2}$, milli = $\times 10^{-3}$, micro = $\times 10^{-6}$, nano = $\times 10^{-9}$.

True or false? J/kg is an acceptable unit for $g$, the acceleration due to gravity (gravitational field strength).

False. The alternative unit for $g$ is N/kg; J/kg is not the same as m/s$^2$.

How can you work out the unit of a quantity from an equation?

Rearrange the equation to make that quantity the subject, then replace every other quantity with its unit, e.g. $k = F/x$ gives N/m.

True or false? 1 hour = 3600 seconds.

True. $60 \times 60 = 3600$ s.

How do you convert a speed in km/h into m/s?

Divide by 3.6: multiply by 1000 (km → m), then divide by 3600 (h → s).

To how many significant figures should the mean of a set of repeated measurements be given?

The same number of significant figures as the measurements.

What is the SI unit of temperature?

The kelvin (K).

What is the resolution of a measuring instrument?

The smallest change in a quantity that the instrument can detect.

How many cm³ are there in 1 m³?

1 000 000 cm³ ($10^{6}$), because 1 m = 100 cm in each of the three dimensions ($100^{3}$).

To how many significant figures should you give the answer to a calculation?

The same number as the data value given to the fewest significant figures.

True or false? In a calculation with several steps, you should round the answer at each step.

False. Keep the unrounded values and round only the final answer, or the result will be less accurate.

How do you estimate the uncertainty in the mean of a set of repeated measurements?

Uncertainty = range ÷ 2, and the result is written as mean ± uncertainty.