Correct Measuring Techniques

How to Use a Scale Correctly

Measuring length seems simple, but small errors can lead to wrong results. Follow these three rules:

1. Placement of the Scale

Place the scale in contact with the object along its length.

• Do not tilt the scale.
• Align the zero mark exactly with one end of the object.

2. Correct Eye Position (Parallax Error)

Your eye must be exactly in front of the point where the measurement is to be taken. If you look from the left or right, the reading will be incorrect. This is called Parallax Error.

3. Measuring with a Broken Scale

If the zero mark is broken or invisible:

1. Start from a full mark (e.g., $1.0 \text{ cm}$).
2. Note the reading at the other end.
3. Subtract the starting mark from the final reading.

Formula:

Example: Start at $1.0 \text{ cm}$, end at $10.4 \text{ cm}$. Length = $10.4 - 1.0 = 9.4 \text{ cm}$.

Measuring a Curved Line

You cannot measure a curved line directly with a straight ruler.

Method:

1. Use a thread or string.
2. Place the thread along the curved line carefully, matching every curve.
3. Mark the start and end points on the thread.
4. Straighten the thread and measure the distance between the marks using a meter scale.