1.1.1 — Describe the use of rulers and measuring cylinders to find a length or a volume

Measuring Length with a Ruler

A ruler is simple, but accurate measurement requires good technique.

Steps for accurate measurement:

• Place the object against the ruler — don’t hold it in mid-air.
• Start at the zero mark, not the edge of the ruler (the edge may be worn).
• Read perpendicular to the ruler to avoid parallax error.
• Read to the nearest millimetre (mm).

Real-world example:

Engineers measuring the length of screws or parts for a machine must avoid parallax errors, or the parts will not fit correctly.

Measuring Volume with a Measuring Cylinder

Used for liquids or irregular solids.

Steps for accurate measurement:

• Place the measuring cylinder on a flat surface.
• Get your eyes level with the liquid’s surface.
• Read from the bottom of the meniscus (the curved surface of the liquid).

For irregular solids, use the displacement method:

• Note the initial water level.
• Submerge the object.
• New volume – initial volume = volume of the object.

Real-world example:

Pharmacists must measure liquid medicines accurately. Reading above the meniscus could lead to overdosing or underdosing.