Foundation of physics Flashcards
What are SI units
units which scientists have agreed to use so that they can easily compare their work
name the seven units and what they measure
Amps- electricity
Candela -light intensity
Moles - amount of a substance
Seconds - time
Metres - displacement
Kelvin - temperature
Kilograms - mass
What are joules in SI units
kgm²s-²
What does femto mean
10^-15
what does pico mean
10^-12
what does nano mean
10^-9
what does micro mean
10^-6
what does milli mean
10^-3
what does kilo mean
10^3
what does mega mean
10^6
what does giga mean
10^9
what does tera mean
10^12
what does peta mean
10^15
what’s the equation of a line
y=mx+c
what are micrometers and Vernier calipers used for
micrometers to measure 0.01mm
calipers for 0.1mm
what is the resolution of micrometers
0.01mm or one hundredth of a mm
what is (usually) the resolution of vernier calipers
0.1mm (one tenth of a mm)
how do you read the scale on micrometers
read the mm mark to the left of the thimble, write down the mms
check if there is a half mm mark before the mm mark, if so add 0.5 to the previous value
read the scale of the thimble where the mm line meets the line on the thimble to find out how many hundredths of a mm to add to your value
(if the line is between hundredths of a mm, write down the lower value)
how do you read the scale on vernier calipers
read the first cm value on the main scale to the left of the vernier scale, write it down
then read the first mm value to the left of the vernier scale on the main scale, add it to the cm value
on the vernier scale, find where the lines on both scales align, this is the tenth of a mm value, add it to the other value to get the final reading
what does the ratchet do on micrometers
prevents the object being measured from being compressed out of shape
how can you take an accurate measurement of an objects diameter
repeat the measurement 5 times at different angles of the object and calculate a mean
what does resolution mean
the smalled possible value that a piece of equipment is able to measure up to
what does uncertainty mean
the interval in which the true value can be expected to lie
what is the absolute uncertainty for a single reading
the smallest division of the value (1, 0.1, 0.01) with a plus minus sign in front of it
how can you find the absolute uncertainty for a range of values
(the greatest value - the smallest value) ÷ 2
how can you calculate percentage uncertainty
(absolute uncertainty ÷ mean value) × 100
what do you do with the uncertainties when adding or subtracting values
add the absolute uncertainties (even if subtracting)
what do you with the uncertainties when multiplying or dividing values
find the percentage uncertainties first
add the percentage uncertainties (don’t subtract)
what happens to the uncertainty when a value is raised to a power
you must find the percentage uncertainty
then you multiply it by the power (don’t raise it to the power)
what do you do to the uncertainty when multiplying by a constant
Multiply the absolute uncertainty by that constant but not the percentage uncertainty.
on which axis do the independant and dependant variables go
independant on x
dependant on y
how can you represent uncertainty on a graph
When you plot points, draw error bars above and below each point
connect the highest point on the first point to the lowest point on the last point
(or vice versa)
you can then calculate a gradient from the line of worst fit.
how can you calculate percentage uncertainty from a graph
((best gradient-worst gradient)÷best gradient)×100
OR
((best y intercept-worst y intercept)÷best y intercept)×100
how can you calculate the percentage difference to find the accuracy of your results
((actual value - your value)÷actual value)×100
define a scalar
a quantity with only magnitude not direction
define a vector
a quantity with magnitude as well as direction
how can you calculate a resultant vector from 2 vectors
dram a resultant rector triangle
use pythagoras’ to find the magnitude
then use trig to find the direction
what rules must you follow when drawing a vector triangle
the lines must be cyclical
the ends of each vector can’t touch
what does it mean to resolve a vector
to find the magnitude of the vectors it is comprised of
