Measurement (CIE IGCSE Physics)

• Rulers can be used to measure small distances of a few centimetres (cm).
  • They are able to measure to the nearest millimetre (mm)

 

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A ruler can measure small distances to the nearest mm

• When measuring larger distances (of a few metres) a tape measure is more appropriate or, when measuring even larger distances, a trundle wheel

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Trundle wheels can be used to measure large distances

• Measuring cylinders can be used to measure the volume of liquids
  • By measuring the change in volume, a measuring cylinder can also be used to find the volume of an irregular shape

 

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Measuring cylinders can be used to determine the volume of a liquid or an irregular shaped solid

Step 1: Measure the length of all four ball-bearings

• • The blocks mark the edges of the first and last ball bearings
  • The blocks make it easier to measure the length of all four ball-bearings

Total length = 12 cm − 4 cm = 8 cm

Step 2: Divide the total length by the number of ball-bearings

Diameter = total length ÷ number of ball-bearings

Diameter = 8 ÷ 4

Diameter = 2 cm

• Stop-clocks and stopwatches can be used to measure time intervals
• An important factor when measuring time intervals is human reaction time. This can have a significant impact upon measurements when the measurements involved are very short (less than a second)

 

Step 1: Identify the start time for the lap

• • The stopwatch was already at 0:55:10 when the runner started the lap
  • Start time =  55.10 seconds (s)

Step 2: Identify the finish time for the lap

• • The stopwatch reads 1:45:10 at the end of the lap
  • Finish time = 1 minute and 45.10 s

Step 3: Convert the finish time into seconds

1 minute = 60 seconds

Finish time = 60 s + 45.10 s

Finish time = 105.10 s

 

Step 4: Calculate the time taken to complete the lap

The time taken to complete the lap = finish time − start time

Time taken to complete lap = 105.10 s − 55.10 s

Time taken to complete lap = 50 s

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• Suppose you have to measure the thickness of a sheet of paper
  • The thing that you are trying to measure is so small that it would be very difficult to get an accurate answer
• If, however, you measure the thickness of 100 sheets of paper you can do so much more accurately
  • Dividing your answer by 100 will then give an accurate figure for the thickness of one sheet
• This process of taking a reading of a large number of values and then dividing by the number, is a good way of getting accurate values for small figures, including (for example) the time period of a pendulum
  • Measure the time taken for 10 swings and then divide that time by 10 to find the average