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How do "uncertainties" work?

Hello! So I'm doing my first physics lab report, and I must include uncertainties... :confused:

So...

Say, I release a ball from a height of 150 cm that I measured. Should I add (+1.00 cm) to it?

Then I got the max height of the first bounce (70 cm) by drawing a little line on the wall and measuring the height.

If after the first bounce I grabbed the ball at its max point to measure the height... do I have to include an uncertainty for that? :confused:

like 70 + 1 cm?

Also, do I have to include the uncertainty for when I measured the height of the line with the metric tape? (+ 0.1 cm) ??

Reply 1

Aaradhana

Any measurement that includes the usage of instruments must include uncertainties.

When you use an analog device, the uncertainty should be half of the least count (for e.g. if you used a ruler to make all these measurements, then your uncertainty is + 0.05 cm)
When you use a digital device, the uncertainty is equal to the least count.

When you grab the ball after its first bounce, you didn't use any instrument, so no uncertainties need to be included. This part will go into your CE (conclusion and evaluation) where sources of error that weren't included in the uncertainties are mentioned.

After some time this stuff will sound very easy and interesting. This is where you score.
Best of luck! :wink: