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igcse physics notesprinted 6 · PDF 6
124 pagesrevision 46936
printed 6 · PDF 6
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A measuring cylinder is filled with some volume of water and then the
irregular object is immersed in it. The change in the level of water indicates
the volume of the irregular object.
Look at the measuring cylinder horizontally and read from the bottom of the
meniscus to avoid parallax error.
Measuring time
Time is measured in seconds (s) and we use digital timers or clocks to
measure it.
Analogue clocks - such as the ones used to tell the time - can be used in
labs to measure time to no better than the nearest second and are usually
suitable for measuring larger intervals of time.
Digital timers such as stopwatches, on the other hand, give a direct reading
of time in numerals and are precise to at least one-hundredth of a second.
For even better precision, automated light gates may be used.
Counteracting Errors
When measuring any physical quantity that may be very tiny, it is likely to
have a lot of errors. To reduce these errors it is best to take a large number
of measurements and take the average. For example, when measuring the
thickness of a sheet of paper, instead of trying to measure the thickness of
one or two sheets, it is better to measure the total thickness of about 200
stacked sheets and then divide the answer by 200 to find the average
thickness of one sheet.