Describe various instruments used for measurement in Physics

Length and Diameter

• Ruler: A straight strip marked with centimeters and millimeters. Used to measure lengths up to 30 cm. The smallest division is usually 1 mm.

• Vernier Calliper: A more precise instrument for measuring small lengths, such as the diameter of a steel ball. It can measure up to 0.1 mm accuracy. It has two jaws: the fixed jaw and the sliding (vernier) jaw.

• Micrometer Screw Gauge: Used for measuring very small thicknesses, like the diameter of a wire. It can measure to an accuracy of 0.01 mm.

Time

• Stopwatch: Used to measure short time intervals, such as the time taken for a pendulum to complete one swing. It can measure to the nearest 0.01 or 0.1 seconds.

• Clock or Watch: Used for measuring longer periods of time, such as hours and minutes.

Mass

• Balance or Scale: Used to compare the mass of an object with known masses. In the laboratory, a beam balance or digital balance is commonly used.

Temperature

• Thermometer: Used to measure temperature. In Physics experiments, we often use mercury or alcohol thermometers. They have a scale marked in degrees Celsius (°C).

Volume

• Measuring Cylinder: A glass container with volume markings used to measure the volume of liquids. The volume is read at the bottom of the meniscus (the curved surface of the liquid).

Force

• Spring Balance (Newton Meter): Used to measure force. It has a spring that stretches when a force is applied. The force is measured in newtons (N).

A vernier calliper has two scales: the main scale (in cm) and the vernier scale (in mm).

Steps to measure the diameter of a steel ball:

1. Place the steel ball between the fixed jaw and the moving jaw.
2. Close the jaws gently until they touch the ball.
3. Read the main scale value just before the zero of the vernier scale. This gives the whole number part (in mm).
4. Look for the vernier scale line that exactly lines up with a main scale line. This gives the decimal part.
5. Add the two values together to get the diameter.

Example: If the main scale reads 12 mm and the vernier scale line that aligns is the 4th line, then the diameter is 12 mm + 0.4 mm = 12.4 mm.

Thermometers have a scale with marks at regular intervals. To read a thermometer:

1. Hold it vertically (upright).
2. Read the level of the liquid at the top of the liquid column.
3. Read the mark on the scale that is level with the top of the liquid column.
4. Always read at eye level to avoid parallax error.

Example: If the mercury level reaches the mark halfway between 30°C and 40°C, the temperature is 35°C.

1. Press the start button to begin timing.
2. Press the stop button to end timing.
3. Read the time displayed on the screen.
4. Press the reset button to return to zero.

Example: A student uses a stopwatch to time a pendulum completing 10 oscillations. If the stopwatch reads 18.5 seconds, then the time for one oscillation (period) is 18.5 ÷ 10 = 1.85 seconds.

In everyday life in Tanzania, measurement instruments are used in many situations. For example, when a farmer at a local market in Dodoma sells maize, they use a balance to measure the mass of the grain to determine the price. Similarly, a nurse at a clinic in Mwanza uses a thermometer to measure a patient's body temperature to check for fever. These instruments help ensure accuracy in trade, health, and daily activities.