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Uncertainty of metre rule ±1mm or ±0.5mm

Question
is the uncertainty of a metre rule ±1mm or ±0.5mm
First one
Reply 2
Original post by Dwarf-Shortage
First one


why?
Reply 3
The shortest increments are 1mm so if you were to get the measurement wrong it could only be by + or - 1mm
Reply 4
If something require a measurement on both sides of something (like a ruler) then you are correct +-0.5mm but on both sides so this makes the total uncertainty +-1mm
Another example of this is a stop watch, you have uncertainty at the start and at the beginning for the uncertainty will be +-0.01 s (if this is the resplution of the stop watch)
Basically you're taking two measurements that involve uncertainty.

One uncertainty from the left hand, one on the other right hand

Same with a stopwatch. Start (1 uncertainty), stop (2 uncertainties)


Uncertainty is half the smallest scale division, so for MEASUREMENTS it's just the smallest scale division

For readings, it's 0.5. Blame AQA and convention
Reply 7
Original post by Rexar
If something require a measurement on both sides of something (like a ruler) then you are correct +-0.5mm but on both sides so this makes the total uncertainty +-1mm
Another example of this is a stop watch, you have uncertainty at the start and at the beginning for the uncertainty will be +-0.01 s (if this is the resplution of the stop watch)


what's a situation where you would have have half a scale division as the uncertainty?
Reply 8
Original post by Arnaez4
what's a situation where you would have have half a scale division as the uncertainty?


For example a voltmeter or an ammeter, a micrometer as well, vernier calliper, scale
Reply 9
vernier calliper is always given as 1 scale division for edexcel :s-smilie:
Reply 10
Measurements (i.e. two readings) - smallest scale division
Readings - half the smallest scale division

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