OK Guys,
- Complete all the tutorials in the Introduction book
- Complete the Prescribed experimental Write up for Acceleration against sin of the angle.
About two periods will be available in class for this.
OK Guys,
About two periods will be available in class for this.
Teamwork by Mr Stewart (Berwickshire HS) and I. He designed and made them and I tweaked them. Thanks Mr Stewart they’re ace!
It is really important that you get to grips with the uncertainty section. You will need this information for your Assignment and it could well form a question on the exam paper.
The key is remembering that ANY measurement is liable to uncertainty. Get that and you’re half way there!
Here is a summary of Key Knowledge for this section new for 2021
Random and systematic uncertainty
Uncertainties and data analysis
Whenever you do an experiment there will be uncertainties.
There are three types of uncertainty and effects to look out for at Higher.
Here the problem lies with the design of the experiment or apparatus. It includes zero errors. Sometimes they show up when you plot a graph but they are not easy to recognise, as they are not deliberate. Systematic effects include slow running clocks, zero errors, warped metre sticks etc. The best way to ensure that these are spotted is to acknowledge their existence and go looking for them. Where accuracy is of the utmost importance, the apparatus would be calibrated against a known standard. Note that a systematic effect might also be present if the experimenter is making the same mistake each time in taking a reading.
These uncertainties cannot be eliminated. They cannot be pinpointed. examples include fluctuating temperatures, pressure and friction. Their effect can be reduced by taking several readings and finding a mean.
These occur because we cannot be absolutely certain about our readings when taking measurements from scales. Use scales with mirrors where possible, good scales and repeat all measurements.
Repeat all experiments to reduce the reading and random uncertainties. Systematic effects are not improved by taking lots of results.
Which experiment has the best design?
This is the best estimate of the “true” value but not necessary the “true” value.
This can be written as and it is sometimes referred to as average deviation or absolute uncertainty.
or
This value indicates how well an instrument scale can be read.
An estimate of reading uncertainty for an analogue scale is generally taken as:
± half the least division of the scale.
Note: for widely spaced scales, this can be a little pessimistic and a reasonable estimate should be made.
For a digital scale it is taken as
± 1 in the least significant digit displayed.
Or uncertainty in reading ÷reading × 100%
When comparing uncertainties, it is important to take the percentage in each.
In an experiment, where more than one physical quantity has been measured, spot the quantity with the largest percentage uncertainty. This percentage uncertainty is often a good estimate of the percentage uncertainty in the final numerical result of the experiment.
eg if one measurement has an uncertainty of 3% and another has an uncertainty of 5%, then the overall percentage uncertainty in this experiment should be taken as 5%
Mrs Physics
January 2022