Measuring Length, Time & Volume
Physics: Cambridge International A Level, topic 1.2.1
Measuring Length
We normally measure length using a ruler. Very small lengths can be measured using a screw micrometer.
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Method
- When using a ruler, it is important to line up the object with the start of the divisions on the ruler.
- To avoid parallax errors (when your eyes and the scale are not lined up), we should read the ruler at right angles.
Measuring very small lengths
- A ruler is not suitable for measuring very small lengths, such as the thickness of a sheet of paper.
- To work out the thickness of one sheet of paper, we can stack together lots of sheets so that the total thickness of the stack can be accurately measured with a ruler.
- The average thickness of one sheet of paper is the total thickness of the stack divided by the number of sheets in the stack.
Screw micrometer gauge
- Small lengths may also be measured with a screw micrometer gauge.
Callipers
- To measure the lengths of objects with a pair of callipers, place the object into the jaws.
- Slide the moving part of the jaw against the object, reading the length of the object from the scale.
Volume
Volume is the amount of space contained in an object.
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Measuring volume
- Measuring cylinders are used to measure volume.
- Read a measuring cylinder with your eye at the level of the liquid.
- Take the reading from the bottom of the meniscus (curve in the surface of a liquid) with the measuring cylinder placed on a flat surface.
Time
Time is measured with stopwatches or timers. Timers can be analogue or digital.
Analogue
- Timers can be analogue, where a pointer moves continuously to tell the time.
Digital
- Some timers do not move continuously to tell the time.
- These are digital timers.
Test yourself on Measuring Length, Time & Volume
Which of these is not a way of measuring length?
Which of the following are true of length measurement?
What is the definition of volume?
Where should your eye be when using a measuring cylinder to read a volume?
When using a measuring cylinder, where should the eye and the cylinder be positioned?