Combining Uncertainties - WORKED EXAMPLE - A Level Physics

This is a worked example on combining uncertainties for A Level Physics. I record some data, calculate the various percentage uncertainties, then combine these and show you how to find the total uncertainty in the volume of a rod.
Thanks for watching,
Lewis
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[@livelygoats]

So for measurements with multiple readings, it doesn't matter what the uncertainty on the measuring device is as you will only use the range and the mean anyway?

[@KittyHello292]

You are the definition of greatness

[@FlixRacing]

THANK YOU! EXAM TOMORROW! Good luck everyone!

[@geoffphillips8183]

Great help, thanks. Never as well explained in books as your vid! 😊

[@usayededu614]

sir love your videos. currently preparing for my As exams in coming may.
Pray I do well.

[@ElPolzerinoUK]

This was a great help, cheers

[@micaiaholubori4999]

Great video

[@platinummlg2774]

can you explain why did u halve 0.01?

[@MrMas9]

For the individual uncertainties of the diameter, shouldn't it be plus or minus 0.005mm (as that is half the smallest division)?

[@PhysicsOnline]

MrMas9 But as it is a measurement there is this error at the start and end measurement, so the total is +/- 0.01

[@kryptictrotium4918]

for readings, you do +- half smallest division, but this is a measurement not a reading, so you do +- smallest scale instead of half of it

[@Darkknight9035]

If the uncertainty in a diameter is .10mm then what is the uncertainty in the radius?

[@hiper_tops]

how do you find %uncertainty of y if y=a+b? where a and b have different units like meters and seconds? Could you even ever have that scenario?

[@user-wx8bm1pg1d]

You cant add 2m meters to 5 seconds . Doesnt Make sense

[@ranonymous27]

A percentage doesn't have a unit, so yes you can add the % uncertainties.

[@simondavid11]

1. The uncertainty of an individual measurement of the diameter should be 0.005 mm as a micrometer is an analogue device.
2. When you combine the uncertainties for the 3 measurements, you got a value lower than the uncertainty of the individual measurement, which is very wrong. To calculate the range, you should have taken the lowest possible and the highest possible values, which then would include the individual uncertainties.

[@nethraabeysekara2076]

👌

[@oliverhume4823]

But for the diameter don't you use the resolution not half the range as the resolution is bigger

[@PhysicsOnline]

Oliver Babcock The process for repeat measurements to find percentage uncertainty is to use half the range divided by the mean.

[@oliverhume4823]

A Level Physics Online but as the half the range value is smaller than the resolution of the apparatus don't you then use the resolution/mean value instead?

[@pokrui8953]

Tips for students: check your exam board and syllabus

[@physicsathome3121]

Physics at home

[@mrboyban]

Completely pointless to have that on the exam!

[@kryptictrotium4918]

yeah but sadly its a part of all 3 sciences