Measuring physical quantities
A physical quantity can be measured and written as a number with a unit.
Scale division is the value of one smallest division between marks.
Error is the unavoidable difference between a measured value and the true value.
Reading = number + unit
Division value = (large mark − small mark) / number of divisions between them
Several measurements → arithmetic mean
Pick the symbol for the quantity.
⏱️
Time
Quantity symbol?
The red mark is the edge of the object (ruler) or the liquid level (thermometer). Read the value at that mark.
Ruler 0–20 cm
Read the scale at the marker (red line).
📏
↑ object edge
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Scale (cm)· division: 0.1 cm
Reading:cm
Find the division value and the reading.
Scale 0–5 s, steps of 0.1 s
Read the scale at the marker (red line).
↑ marker
0
1
2
3
4
5
Scale (s)· division: 0.1 s
Reading:s
Division value:s
Calculate the arithmetic mean of the readings.
Readings:
15.315.515.4
Arithmetic mean of readings (enter a number)