Errors, Percentage Uncertainties and Compound Errors - A Level Physics Revision

A run through of how to calculate uncertainties and errors in A Level Physics. Percentage errors and compound errors as well. Thanks.

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[KitBetts-Masters]

Many of you have asked should absolute uncertainty be + or - half a scale division or one full. I read in the specifications either will be accepted.

[gravinboginagis]

You're a brilliant teacher man. Very helpful 👍

[raffirahmansyah]

Thank you. This is the first time I've learned physics in a cave

[ali-bbso]

Hi,
In my AS mock paper it asked for the uncertainty in the value 3.5 * 10^-3. I thought i was 0.05*10^-3 as that is half thesmallest incrament, but in the markscheme it says 0.1*10^-3. Do you undertand why?

[jimohara]

For the last example you calculate the velocity. But to find the error wouldn't you have to take the upper bound of the distance and the lowest bound of time to get the biggest value possible, and the lower bound of distance and upper bound of time to find the lowest value of uncertainty? Why does it work by just adding the uncertainties instead? Hope that makes sense

[harrisonbennett]

Sir I have a question in the final value quoted does the value and the absolute uncertanty have to have the same number of decimal places sig figs or both?

[KitBetts-Masters]

Grab my new book to help you get ready for studying A Level Physics and to prepare for the exams:

[wajahatahmed]

Umm, were you measuring to the nearest 0.1 cm ? Because half a scale of a division of cm would be 0.5 cm not 0.05 cm, right ? And for the constant velocity example, were you still measuring to the nearest 1 cm ?

[rohinpithwa]

Doesn't scale have a zero error? Shouldn't the uncertainty be 1mm instead of 0.5mm?

[syedfahim]

precision of metre rule is 1mm, isn't it? then why are you using 0.05cm?
could you explain please.
tia