Physics paper 3 (practical) A+level
(AQA)
Name the SI base units - ANS-metre - m
kilogram - kg
second - s
ampere - A
kelvin - K
mole - mol
candela - cd
what are random errors, how do they arise and how can they be reduced? - ANS-they
cause readings to randomly fluctuate about the mean affecting precision
due to observational or reading errors
or due to the environment e.g varying temperature or supply voltage
you cannot reduce random error but you can reduce their effect by taking repeat
readings and taking an average
what are systematic errors, how do they arise and how can they be reduced? -
ANS-systematic errors cause each reading to be consistently wrong, cause every result
to differ from the true value by the same amount affecting accuracy
due to:
-instrument error: the instrument has not been calibrated properly
-reading error: for example parallax error that will affect all readings -poor
experimental design: for example ignoring the affect of an external factor
it is hard to spot if they are there in the first place
but you can:
-redo the experiment with a different method
-you can calibrate your apparatus which will reduce zero errors
, what does it mean if a result is repeatable and reproducible? - ANS-repeatable- if the
experiment is repeated by the experimenter an gives consistent results
reproducible- if other experimenters can get similar results with different methods
what do precision and accuracy tell you? - ANS-precision- tells you whether the results
are numerically close together
accuracy- how close a result is to the true value
how can you increase the percentage uncertainty and thus the precision of repeatable
events? - ANS-measure the time over multiple events
thus sharing the absolute uncertainty across a greater overall reading so the percentage
uncertainty will decrease.
how do you obtain the overall uncertainty if you are adding or subtracting quantities? -
ANS-you need to add their absolute uncertainties
how do you obtain the overall uncertainty if you are multiplying or dividing quantities? -
ANS-you need to add their percentage uncertainties
how can you overcome the uncertainties for each measurement on a graph and how do
you decide what the gradient is - ANS-uncertainty in each measurement- use 'error
bars' and draw a best fit line that goes through all the error bars
uncertainty in best fit line- draw two lines of best fit one with the maximum gradient
going through all error bars and the other with the minimum gradient going through all
error bars.
-find the range of the two gradients and divide by two for the absolute error in the
gradient
what are valid results? - ANS-a valid result arises from a suitable procedure to answer
the original question, keeping all the other variables controlled bar the one that you are
investigating
what areas must you look at when evaluating a method? - ANS--whether all the
variables are controlled, if not how could they be controlled
(AQA)
Name the SI base units - ANS-metre - m
kilogram - kg
second - s
ampere - A
kelvin - K
mole - mol
candela - cd
what are random errors, how do they arise and how can they be reduced? - ANS-they
cause readings to randomly fluctuate about the mean affecting precision
due to observational or reading errors
or due to the environment e.g varying temperature or supply voltage
you cannot reduce random error but you can reduce their effect by taking repeat
readings and taking an average
what are systematic errors, how do they arise and how can they be reduced? -
ANS-systematic errors cause each reading to be consistently wrong, cause every result
to differ from the true value by the same amount affecting accuracy
due to:
-instrument error: the instrument has not been calibrated properly
-reading error: for example parallax error that will affect all readings -poor
experimental design: for example ignoring the affect of an external factor
it is hard to spot if they are there in the first place
but you can:
-redo the experiment with a different method
-you can calibrate your apparatus which will reduce zero errors
, what does it mean if a result is repeatable and reproducible? - ANS-repeatable- if the
experiment is repeated by the experimenter an gives consistent results
reproducible- if other experimenters can get similar results with different methods
what do precision and accuracy tell you? - ANS-precision- tells you whether the results
are numerically close together
accuracy- how close a result is to the true value
how can you increase the percentage uncertainty and thus the precision of repeatable
events? - ANS-measure the time over multiple events
thus sharing the absolute uncertainty across a greater overall reading so the percentage
uncertainty will decrease.
how do you obtain the overall uncertainty if you are adding or subtracting quantities? -
ANS-you need to add their absolute uncertainties
how do you obtain the overall uncertainty if you are multiplying or dividing quantities? -
ANS-you need to add their percentage uncertainties
how can you overcome the uncertainties for each measurement on a graph and how do
you decide what the gradient is - ANS-uncertainty in each measurement- use 'error
bars' and draw a best fit line that goes through all the error bars
uncertainty in best fit line- draw two lines of best fit one with the maximum gradient
going through all error bars and the other with the minimum gradient going through all
error bars.
-find the range of the two gradients and divide by two for the absolute error in the
gradient
what are valid results? - ANS-a valid result arises from a suitable procedure to answer
the original question, keeping all the other variables controlled bar the one that you are
investigating
what areas must you look at when evaluating a method? - ANS--whether all the
variables are controlled, if not how could they be controlled
