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Specification Point 2.3 OCR A Physics A-Level
What is the typical value for the mass of a person
70kg
What is the typical value for the mass of a car
1500kg
What is the typical value for the height of a man
1.8m
What is the typical value for the walking speed
1.5ms^-1
What are the 2 types or errors
Random errors
Systematic errors
What is a random error
Random errors cause readings to be spread about the true value due to the results varying in an unpredictable way.
What does a random error effect
Precision
Can you completely prevent random errors
No you can try lessen their effect but can never completely remove them
Name 2 examples of a random error
Different head position when reading of a ruler
Can’t keep the control variables the same
How can you lessen the effects of random errors
-Use more sensitive apparaturs
-Repeating measurements and finding the mean
What is a systematic error
Systematic errors usually cause readings to be different to the true value by the same amount
What does systematic errors effect
Accuracy
Name 2 examples of systematic errors
-Using an inaccurate scale
-Repeating the same mistake
Can systematic errors be removed completely
Yes with proper scientific technique systematic errors can be removed and cause negligible effects on your experiment
How can you remove systematic errors
Calibrate the apparatus to make sure there is no 0 error
What is the absolute uncertainty
The total uncertainty for a measurement
What is the percentage uncertainty
The uncertainty given as a percentage of a measurement
How do you calculate the absolute uncertainty
Or determine if the calculation is a reading or a measurement and if its been taken by a digital or analogue apparatus
Digital = the uncertainty is the resolution of the equipment
Analogue = half the uncertainty of the equipment
Reading = only taken once
Measurement = taken twice so uncertainty is doubled
How to calculate the percentage uncertainty
What is the order of magnitude
Rounded up to the nearest power of 10
What amount of significant figures should you give your answer to
The smallest number of significant figures in the question.
How do you add or subtract uncertainites
Add the absolute uncertainites
How do you multiply or divide uncertainites
You add the percentage uncertainties
How do you raise an uncertainty to a power
You multiply the percentage uncertainty by the power
What is the percentage difference
If you know the true value and want to measure the accuracy of your results you can use the percentage difference
What is the calculation for percentage difference
What is the definition of precise
The smaller the amount of spread of your data from the mean the more precise it is
What is the definition of repeatable
If you can repeat the experiment multiple times and get the same results
Definition of reproducible
If someone else can do the experiment and get the same results as you
What is a valid result
A result that answers the question using precise data
What does an error bar show
The uncertainty on a graph
How do you find the uncertainty from a gradient
Draw a line of worst fit
What 2 worst fit lines are there
A maximum worst fit
A minimum worst fit
How do you draw a line of worst fit
Going through all the error bars
Note 
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