9th Class Physics Unit No.1 Physical Quantities and Measurement Notes
In the awe-inspiring world of science, the 19th century marked a significant division of the physical sciences into five distinct disciplines: physics, chemistry, astronomy, geology, and meteorology. Among these disciplines, Physics stands as the most fundamental, laying the groundwork for our understanding of the natural world. In the realm of Physics, we explore matter, energy, and their intricate interactions, unraveling the laws and principles that govern the very fabric of nature.
The rapid strides of scientific progress in recent years owe their existence to the remarkable discoveries and inventions in the field of Physics. These scientific advancements have given birth to countless technologies that shape our modern society across the globe. From the mechanics behind automobiles to the principles of thermodynamics that fuel our refrigerators, Physics is the guiding force behind our cutting-edge technologies.
Indeed, Physics permeates every facet of our daily lives. From the pulleys that effortlessly lift heavy loads to the vast networks of electricity powering our world, Physics is ever-present. Consider the marvels of modern communication – the mobile phone – a device that fits in the palm of our hands, revolutionizing how we interact with the world. All these technological wonders, made possible by the principles of Physics, have enriched our lives, making them easier, faster, and more comfortable.
However, the power of scientific inventions also carries the potential for harm and destruction, manifesting in environmental pollution and the creation of deadly weapons. It is a reminder of the responsibility that comes with the pursuit of knowledge and discovery.
- Chapter No.1 Introduction to Biology
- Chapter No. 2 Solving a Biological Problem
- Chapter No.3 Biodiversity
- Chapter No.4 Cells and Tissues
- Chapter No.5 Cell Cycle
Branches of Physics
Physics, being a vast and diverse field, is further divided into various branches, each focusing on specific aspects of the physical universe. Some of these branches include:
Mechanics: The study of motion, its causes, and effects.
Heat: Examining the nature of heat, modes of transfer, and its effects.
Sound: Delving into the physical aspects of sound waves, their production, properties, and applications.
Light (Optics): The study of the physical aspects of light, its properties, working, and the use of optical instruments.
Electricity and Magnetism: Exploring charges at rest and in motion, their effects, and their relationship with magnetism.
Atomic Physics: Investigating the structure and properties of atoms.
Nuclear Physics: Delving into the properties and behavior of nuclei and the particles within them.
Plasma Physics: The study of the production and properties of the ionic state of matter – the fourth state of matter.
Geophysics: Understanding the internal structure of the Earth.
Physical Quantities and Measurement
At the core of Physics lies the concept of physical quantities and measurement. These quantities encompass length, mass, time, temperature, and others, each characterized by a numerical magnitude and a specific unit of measurement. Physical quantities are classified into base quantities and derived quantities, forming the foundation for various other quantities expressed in terms of them.
International System of Units (SI)
The quest for a universally accepted system of units culminated in the creation of the International System of Units (SI). This global system of measurements provides standardized units for various physical quantities, making it easier to exchange scientific and technical information worldwide. SI units include base units like meter, kilogram, second, and derived units such as area, volume, speed, force, and more.
Prefixes and Scientific Notation
To facilitate the expression of extremely large or small numbers, SI units employ prefixes such as kilo, mega, giga, and milli. These prefixes simplify the representation of quantities, making them more manageable and understandable. Additionally, scientific notation allows us to express numbers as a product of a power of ten and a number between 1 and 10, aiding in efficient communication and calculation.
Physics is the gateway to unraveling the mysteries of the universe. With its principles guiding the way, we embark on an endless journey of discovery and innovation, transforming our world for the better while mindful of our impact on the environment and society. So, let us dive into the captivating world of Physics, where understanding nature leads to remarkable insights and breakthroughs.
Measuring Instruments
I. Introduction
Measuring instruments are used to measure physical quantities such as length, mass, time, and volume.
The reliability and accuracy of measuring instruments have improved over time.
Some common measuring instruments used in physics laboratories are the metre rule, Vernier callipers, micrometer screw gauge, physical balance, and stopwatch.
II. The Metre Rule
The metre rule is used to measure length with an accuracy of 1 mm.
It consists of a scale with centimetre and millimetre markings.
The correct reading is obtained by aligning the eye with the markings on the scale.
III. Vernier Callipers
Vernier callipers offer higher accuracy (less than 1 mm) than the metre rule.
It has a main scale and a vernier scale with 10 divisions, each representing 0.9 mm.
The difference between one main scale division and one vernier scale division is called the least count (LC).
IV. Using Vernier Callipers
To find the diameter of an object, close the jaws gently and note the zero error.
Take multiple readings with the object displaced or rotated to get accurate results.
Zero error can be positive or negative depending on the alignment of the scales.
V. Micrometer Screw Gauge
Micrometer screw gauge offers even higher accuracy (0.01 mm) compared to Vernier callipers.
It consists of a spindle and a thimble with a circular scale representing 0.01 mm per division.
VI. Using Micrometer Screw Gauge
To measure the diameter of an object, determine the zero error and apply zero correction.
Take multiple readings with different standard masses to balance the object’s mass.
VII. Lever Balance and Electronic Balance
Lever balance and electronic balance are used to measure mass.
Electronic balances provide the most precise measurements.
VIII. Stopwatch
A stopwatch is used to measure time intervals.
Mechanical stopwatches have a start-stop button, while digital stopwatches have additional features.
IX. Measuring Cylinder
Measuring cylinders are used to measure the volume of liquids and irregularly shaped solids.
The correct method to read the meniscus is by aligning the eye at the same level as the liquid surface.
Significant Figures
The accuracy of measurements is expressed by significant figures. Significant figures are the reliable digits in a measured value.