Measurement of Length

Measurement of Length

• Measured using a metre rule
• SI Unit of length is the metre (m)

Prefixes of Metre

• $1$ m → $100$ cm
• $1$ km → $1000$ m

Class Activity 1: Measure thickness of one slotted mass

a) Process

1. Take 3 slotted masses and stack them together.
2. Measure the combined height (e.g., 3 cm).
3. Thickness of one mass = Total height ÷ number of masses (e.g., $3 \div 3 = 1$ cm).

b) Sources of errors / uncertainty

• Parallax error: Reading the value when eyes are not perpendicular to the scale.
• Not measuring from the zero line of the metre rule.

How to minimise error

• Position eye level perpendicular to the scale (non-parallax method).
• Place the metre rule directly against the object.

Thickness / External Diameter of a Tube

Process

1. Put boiling tube between two wooden blocks.
2. Measure the distance of separation with the ruler.

Precautions

1. Avoid measuring at the lips of the boiling tube.