2.1 - Quantities and units Flashcards
What is a physical quantity?
A physical quantity is a property of an object or of a phenomenon that can be measured
What happened to the NASA Mars Climate Orbiter?
It arrived at Mars earlier than anticipated, and disintegrated in the upper atmosphere
Why did the Climate Orbiter disintegrate?
One of NASA’s teams worked in feet and pounds, whilst the other team worked in metres and kilograms. Each team assumed the other was using the same units
How do you use a Vernier calliper to measure the length of an object?
- Place the calliper into the object
- See where the first line lines up with the object and note where / the ranges of the length
- Then, look at the Vernier scale. See which one lines up with the value on the main scale. and this is the next value for the length
How do you use a micrometer to measure the length of an object?
- Place object into micrometer and tighten
- Read the first / barrel scale
- Read the second barrel scale to work out hundredths of mm - add on if 1/2 mm
What quantities are just numbers?
Proton number, efficiency and magnification
Have a numerical magnitude / size, but no units
What quantities have numbers and units?
Length, speed
What are SI units?
Système International d’Unités (International System of Units)
a standard system of units
What are the seven SI base units?
length, metres, m
mass, kilograms, kg
time, seconds, s
electric current, ampere, A
temperature, Kelvin, K
amount of substance, mole, mol
luminous intensity, candela, cd
Why are some symbols written in capital letters?
They are named after a person
What are the SI prefixes?
Prefix name, prefix symbol, factor
peta, P , 10^15
tera, T, 10^12
giga, G, 10^9
mega, M, 10^6
kilo, k, 10^3
deci, d, 10^-1
centi, c, 10^-2
milli, m, 10^-3
micro, u, 10^-6
nano, n, 10^-9
pico, p, 10^-12
femto, f, 10^-15
