Measurements- Points to remember

📏 IIT Foundation Physics – Class 8
Chapter 1: Measurement

Measurement is the foundation of Physics. Every experiment, calculation, and observation begins with measuring physical quantities. Let us go through the important points from this chapter.

🔑 Points to Remember

• The quantities that can be measured are called physical quantities.
• A quantity which is independent of other quantities is called a fundamental quantity.
• A quantity which depends on other quantities and can be derived from the fundamental quantities is called a derived quantity.
• The unit of a fundamental quantity like mass or length is called a fundamental unit.
• The unit of a derived quantity like volume or velocity is called a derived unit.
• A system which defines the fundamental units, in comparison with which a fundamental quantity can be expressed, is referred to as a system of units.
• 1 metre is defined as 1,650,763.73 times the wavelength of orange light emitted by a krypton atom at normal pressure.
• 1 kilogram is the mass of a certain lump made from an alloy of platinum-iridium maintained at 0°C in the International Bureau of Weights and Measures.
• 1 second is defined as ¹/_86,400 part of the mean solar day.
• Least count of an instrument is the smallest measurement that the instrument can make accurately.
• Vernier calliper is an instrument with a combination of two scales – the main scale and the vernier scale – used to measure small lengths with accuracy.
• Area is the extent of a surface. SI unit = m². (1 m² = 100 cm × 100 cm = 10,000 cm²).
• Measuring jar is graduated in millilitres and is used to measure the volume of partial liquids.
• Burette has a nozzle at the bottom with a screw system, graduated in millilitres. It is used to take the desired amount of liquid accurately.
• Mass is the amount of matter contained in a body. It is a fundamental quantity and its SI unit is kilogram (kg).
• Density of a substance is defined as mass per unit volume. SI unit = kg/m³.
• The ratio of the density of a substance to the density of water is called relative density or specific gravity. It is a pure number without units.
• Specific gravity bottle (or density bottle) is a glass bottle with a narrow neck and fitted stopper with a hole, designed to hold a specific volume as indicated.

🌟 Tip: Always remember, measurement is the first step in Physics. Without precise measurement, scientific laws cannot be applied correctly.

In the next post, we will solve examples and practice MCQs based on this chapter to strengthen your understanding.