appendics and chapter 2

Question 1

rule for calculations and table of results

Answer 1

Use the least amount of significant figures used for a value in the calculation

Question 2

rules for plotting graphs

Answer 2

independent variable on x, dependent on y
don’t use multiples of 3 7 11 or 13 for scales
used majority of page to plot results
use small crosses to mark points
use a large triangle for the gradient,more than have the line
use a long ruler for line of best fit

Question 3

what are measurement errors

Answer 3

the difference between the true value and the measured value

Question 4

what are random errors and how can they be stopped

Answer 4

errors that occur unpredictably from :
uncontrollable/ unknown factors
difficulty in deciding the reading on a measuring device

they can’t be stopped but they can be minimised by repeating measurements and taking the mwan

Question 5

what are systematic errors?

Answer 5

errors that are consistently differing from that true value each time

caused by faulty measuring devices(ones with zero error)
or faulty method of taking measurements

can be stopped by getting new equipment / recalibrating equipment

Question 6

precision vs accuracy

Answer 6

accuracy - how close a measurement is to the true value of
precision - how close together repeated measurements are to each other

Question 7

what is uncertainty, absolute uncertainty and percentage uncertainty

Answer 7

uncertainty is the interval in which the true value can be expected to lie
absolute uncertainty - can be approximated as the mean value plus minus the half of the range
percentage uncertainty - absolute uncertainty / mean value x 100

Question 8

How can the absolute uncertainty be approximated with a single reading or identical values

Answer 8

using the resolution of the measuring device, the smallest change in the measured quantity the instrument can show

Question 9

rules for analysing uncertainties

Answer 9

1. when adding or subtracting , add the absolute uncertainties
2. when multiplying or dividing, add the percentage uncertainties
3. when raising to a power, multiply percentage uncertainty by the power

Question 10

uncertainties from a graph

Answer 10

draw a graph with error bars (line of best fit must fit throw the error bars)
make a line of worst fit(the steepest or shallowest line possible in the error bars)
the absolute uncertainty is the positive difference between the gradient of the two lines

percentage uncertainty is the absolute uncertainty/ gradient of line of best fit x 100