Types of Measurement Tools: Measurement in Scientific Work - Physics (Grade 10)

Why Measurement Matters

Every time we weigh food ingredients, look at a speedometer, read body temperature, or measure the length of a table, we are measuring something. In physics, measurement means comparing a quantity with a standard unit.

\text{measurement result} = \text{measured value} \times \text{unit}

For example, if the length of an object reads $8 \text{ cm}$ , then $8$ is the measured value and $\text{cm}$ is the unit.

The right measuring tool makes a result useful. The wrong tool can make an answer look neat, but still fail to match the object being measured.

Explore Measurement Tools

Use this small lab to compare three basic measurement tools. Rotate the model, then notice what is measured, which unit appears, and how the reading is interpreted.

Measurement Tools Lab

Choose a tool to see the relationship between the quantity, measured object, and reading.

Block length

3.8 \text{ cm}

Instrument: Ruler
Measured object: Small block
Reading: $3.8 \text{ cm}$

Choosing a Measurement Tool

Before measuring, first ask: what quantity do we want to find? From that question, the measuring tool and unit become clearer.

mermaid

SI is the international abbreviation for Système international d’unités, the International System of Units. In practice, SI is the shared standard that lets measurements from different schools, laboratories, and countries be compared in the same language.

In SI, base quantities that often appear at the start of physics include length, mass, and time. Their base units are $\text{m}$ for length, $\text{kg}$ for mass, and $\text{s}$ for time.

Reading Measurement Results

Length

When reading a ruler, do not only look at the number at the end of the object. Also check the starting position. If the object starts at $0 \text{ cm}$ and its end is at $8 \text{ cm}$ , the result is:

\begin{aligned} \text{object length} &= 8 \text{ cm} - 0 \text{ cm} \\ &= 8 \text{ cm} \end{aligned}

If the object starts at $1 \text{ cm}$ and ends at $7 \text{ cm}$ , its length is not $7 \text{ cm}$ .

\begin{aligned} \text{object length} &= 7 \text{ cm} - 1 \text{ cm} \\ &= 6 \text{ cm} \end{aligned}

Mass

A balance is used to measure mass, the amount of matter in an object. If the balance reads $250 \text{ g}$ , then the object's mass is:

m = 250 \text{ g}

In the lab above, the balance is modeled as an equal-arm balance. The object sits on the left pan, while a $250 \text{ g}$ reference mass sits on the right pan. If the object mass is greater than $250 \text{ g}$ , the object side moves down. If it is smaller than $250 \text{ g}$ , the reference side moves down. If both masses are equal, the balance is in equilibrium.

\begin{aligned} \tau_\text{left} &= r m_\text{object} g \\ \tau_\text{right} &= r m_\text{reference} g \\ m_\text{object} = m_\text{reference} &\Rightarrow \tau_\text{left} = \tau_\text{right} \end{aligned}

For full SI writing, the mass can be converted to kilograms.

\begin{aligned} 250 \text{ g} &= 250 \times 10^{-3} \text{ kg} \\ &= 0.25 \text{ kg} \end{aligned}

Time

A stopwatch is used when we want to measure the duration of an event. If the stopwatch reads $12.8 \text{ s}$ , the event lasts for $12.8$ seconds.

t = 12.8 \text{ s}

Measurement Tools Around Us

Rulers and tape measures help measure table length, body height, or short distances.
Vernier calipers help measure outside diameter, inside diameter, or the depth of small objects.
Micrometer screw gauges help measure the thickness of very small objects, such as thin wire.
Balances help measure the mass of objects.
Thermometers help measure temperature.
Stopwatches help measure the duration of events.
Speedometers help measure vehicle speed.

Check Your Understanding

A pencil is placed on a ruler. The left end of the pencil is at $2 \text{ cm}$ , while the right end is at $15 \text{ cm}$ . The pencil length is:

\begin{aligned} \text{pencil length} &= 15 \text{ cm} - 2 \text{ cm} \\ &= 13 \text{ cm} \end{aligned}

So, the pencil length is $13 \text{ cm}$ .

From the pencil example, the measurement pattern becomes visible: first identify the quantity, then choose a suitable tool, then write the result with its unit. When those $3$ parts are clear, the measurement is not just a number. It can be compared and used in later scientific work.