# Measurements

Measurements are a part of our daily lives, right from measuring volume of edible liquids, to measuring the speed of light!

In this guide, we are going to put forward some important revision points that may come useful during your IGCSE examinations. All the very best!

## Types of measurements

• Measurement of length
• Measurement of volume
• Measurement of Time

## Measurement of length

Length is measured accurately through many methods. Here are some:

 Method Notes Diagram Ruler Used to make simple measurements accurate to 0.1 cm (1 mm) Vernier caliper Used to make simple measurements accurate to 0.01 cm (0.1 mm) Micrometer screw gauge Used to make simple measurements accurate to 0.001 cm (0.01 mm)

### How to measure length using a vernier caliper

1. Place the object between the jaws of the vernier caliper
2. Measure and note the length of the object on the main scale by looking at the left of the 0 on the vernier scale.
3. This tells you the length in millimetres.
4. Now, observe the vernier scale;
5. Find the point where one of the markings on the vernier scale is exactly aligned with one on the main scale
6. This tells you the fraction of a millimetre that you must add to the main scale reading.

Take the example below:

<Image for using vernier calipers here>

### How to measure length using a micrometer screw gauge

1. Read the main scale to nearest 0.5mm
2. Read the additional fraction of a millimetre from the fractional scale.
3. Add both the readings and get the thickness of the object

<Image for using micrometer screw gauge here>

## Measurement of volume

 Measuring regular shaped objects Use formulae to find their volumes; if it is a cube, then measure the length of one side and multiply it by 3 Measuring irregularly shaped objects Use displacement method: a. Pour some water in the measuring cylinder and record its volume (V1). b. Submerge the object in the water. c. Record the reading of the water level in the cylinder (V2). d. Use the formula Vx=V1-V2 to find the volume of the object. Measuring liquids Use a measuring cylinder

# Density

Density is the ratio of mass to volume for a substance.

Measuring density

The most accurate way to calculate the density of any solid, liquid or gas is to divide its mass in kilograms by its volume (length × width × height) in cubic meters.

Density is calculated using the equation: The unit for density is kg/m3.

## Facts on density

• Gases have lower densities than liquids
• Density of water is 1000 kg/m3
• Density depends on the composition of the material
• The amount of a metal in an alloy is found by measuring its density

## Measuring time

Time is measured in a laboratory using stop-clocks and stopwatches. Measuring time is essential; especially when calculating speed and acceleration.

For improving the accuracy, light gates and electronic timers need to be used during experiments involving motion.

### Intervals of time is measured using a pendulum:

• A pendulum is made to swing 10 times with a stopwatch running simultaneously.
• The time taken for one swing is found out by dividing the total time for 10 swings by 10.

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