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Physical World can be defined as the study of the physical world and matter, as well as their movement through space and time. It include topics such as energy, force, etc. Physics can be described as a study of the basic fundamental laws of nature and their manifestation in different natural phenomena.
- The physical world includes all the natural occurrences in the universe.
- It is a fundamental discipline that comes under the category of natural sciences.
- Physical World also includes chemistry and biology.
- In physics, the subject of matter includes the atoms' structure, magnetism, electricity and sound.
- It also includes mechanics, gravity, heat, light, and radiation.
- There are four fundamental forces: Gravitational Force, Electromagnetic Force, Strong Nuclear Force, and Weak Nuclear Force.
Read More: Principle of Homogeneity of Dimensions
Key Terms: Physical World, Physics, Chemistry, Biology, Force, Magnetism, Law of Nature, Fundamental, Charge, Electricity
Physical World
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Physical World can be defined as nature's complexity, and resolving its own complexities will provide us with new insights into it. In other words, it can be said that it is a study of nature in order to learn how the world around us functions.
- Physical World gives a insight about understanding of the past and the development of nature’s laws.
- It is associated with physical world.
- It include wide range of physical quantities such as mass, length and energy.
- Physical World help us understand about control and modification mechanism of science.
- It acquire knowledge about the surroundings through observations, and experiments.
Read More: Fundamental and Derived Units of Measurement
Scope of Physics
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The scope of physics can be understood with two domains; the microscopic domain and the macroscopic domain.
Microscopic Domain
Microscopic Domain includes atomic, molecular, and nuclear phenomena. It is concerned with the structure and composition of matter. The domain includes microscopic scales of atoms and nuclei (and even lower length scales).
- It involves interactions with various probes such as electrons, photons, and other particles.
- Quantum theory is accepted as the framework for explaining microscopic domain.
- Classical physics is insufficient for the microscopic domain.
Read More: Unit Conversion
Macroscopic Domain
Macroscopic domain includes phenomena at the laboratory, terrestrial and astronomical scales. Classical Physics deals with macroscopic phenomena and includes subjects like Mechanics, Electrodynamics, Optics, and Thermodynamics.
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Fundamental Forces of Nature
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Forces play an important role in our lives on a daily basis, from lifting a glass of water to pushing or throwing an object. In nature, there are four fundamental forces observed: Gravitational force, Electromagnetic Force, Strong Nuclear Force, and Weak Nuclear Force. Without the existence of any of these forces, all the matter in the universe will disintegrate.
Gravitational Force
Gravitational force is a mutual force of attraction between any two objects due to their masses. It is a universal force. Like every other object in the universe, every object feels this force.
- For example, all the objects on Earth are subjected to the Earth's gravitational pull.
Newton's law of gravity states that "the gravitational force between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them".
Electromagnetic Force
Electromagnetic force between charged particles states that when the charges are at rest, they are attractive for unlike charges and repulsive for like charges. Magnetic effects are produced when the charges are in motion, and a magnetic field produces a force on a moving charge.
Read More: Applications of Gauss’s Law
Strong Nuclear Force
In a strong nuclear force, the protons and neutrons are held together in a nucleus. The force is strong enough to overcome the repulsion between its charged protons. It is charge-independent and acts equally between a proton and a proton, a neutron and a neutron, and a proton and a neutron.
Weak Nuclear Force
The weak nuclear force appears only in certain nuclear processes, such as β decay of the nucleus. The nucleus emits an electron along with an uncharged particle known as a neutrino during decay. The weak nuclear force is much weaker than the strong nuclear and electromagnetic forces but not as weak as gravity.
Read More: Force multiple charges
Properties of Fundamental Forces
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The properties of fundamental forces are as follows:
| Name | Relative strength | Range | Operates among |
|---|---|---|---|
| Gravitational force | 10–39 | Infinite | All objects in the universe |
| Strong nuclear force | 1 | Short, Nuclear, (∼10–15m) | nucleons heavier size elementary particles |
| Weak nuclear force | 10–13 | Very short, Sub-nuclear size (∼10–16m) | Some elementary particles, particularly electron and neutrino |
| Electromagnetic force | 10–2 | Infinite | Charged particles |
Read More: Electric Dipole
Nature’s Laws of Conservation
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In any physical phenomenon, some special physical quantities are invariant. These nature's conserved quantities are known as energy, mass, charge, linear momentum, and angular momentum.
Respective to these quantities, physics has a few laws of conservation, which are as follows;
Laws of Conservation of Energy
Laws of Conservation of Energy states that energy can neither be created nor be destroyed. It can only be transformed from one form to the other.
Laws of Conservation of Angular Momentum
The laws of Conservation of Angular Momentum state that when no torque is applied to the system, total angular momentum remains conserved. Because a rotating body has inertia, it also has momentum associated with its rotation. This momentum is known as angular momentum.
Read More: Electroscope
Laws of Conservation of Linear Momentum
Laws of Conservation of Linear Momentum states that in the absence of an external force, a system's linear momentum remains constant, represented by P, and the expression is P = mv.
Laws of Conservation of Charge:
Laws of Conservation of Charge state that charges (in the form of electrons) are neither created nor destroyed but rather transferred from one body to another.
Read More: Electrical Insulators
Things to Remember
- The physical world remains unchanged in a process and is called conserved quantities.
- Physics and technology are strongly intertwined.
- Sometimes, technology creates new physics, and other times, physics creates new technology.
- Nuclear force is the strongest of all the fundamental forces.
- It is about 100 times the electromagnetic force in strength.
- Gravity is always attractive, while electromagnetic force can be attractive or repulsive.
- Mass comes only in one variety, but charge comes in two varieties: positive and negative charge.
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Sample Questions:
Ques. Which is the strongest fundamental force in nature? (2 Marks)
Ans. The electromagnetic force is the strongest fundamental of nature out of all the four forces. It is also known as the Lorentz force. Electromagnetic force takes place between two charged particles via electromagnetic fields. When current is applied across the circuit, it will induce the required magnetic field in the circuit. The force can be explained with the help of the fleming right-hand rule.
Ques. Describe the term science? (3 Marks)
Ans. Science systematically attempts to understand natural phenomena in such detail and depth that they can be predicted, modified, and controlled. It requires a flexible and open-minded approach towards solving problems. It is divided into two main branches of science, namely physical science and biological science. The working of science is based on four steps, which are as follows:
- Experimentation and observation of objects.
- Formation of required hypothesis.
- Verification of Hypothesis done on the object
- Lastly, the predictions made on the object.
Ques. What are the conserved quantities of nature? (3 Marks)
Ans. The quantities which remain constant with respect to time are called conserved or constant quantities of nature. These conserved quantities can be used as a function, including adding a number. In the world of physics, it can be explained with an example of kinetic energy and mechanical energy. The kinetic and potential energy changes with respect to time. On the other hand, total mechanical energy, which is the sum of kinetic and potential, remains constant with time.
Ques. What is Natural Science? (2 Marks)
Ans. Natural Science can be defined as a branch of science concerned with the description, prediction, and comprehension of natural phenomena. It includes disciplines such as physics, chemistry, and biology. The entire process is based on empirical evidence from experimentation and different observations. It is of two types, namely physical science and life science.
Ques. Why is physics called an exact science? (2 Marks)
Ans. Physics is all about the measurements of fundamental quantities. It helps us study the behaviour of space with respect to time. Physics also explains the relationship between energy and force. Unification and reduction are two principles on which the working of physics is based. Therefore, physics is also called an exact science.
Ques. Differentiate between gravitational force and electromagnetic force in nature? (3 Marks)
Ans. The key differences between gravitational and electromagnetic forces are tabulated below:
| Gravitational force | Electromagnetic force |
|---|---|
| Gravitational force acts on the object due to gravity. | The electromagnetic force acts on charged particles. |
| It acts on any object that has mass. | It acts on either charged particles or iron-containing particles. |
| It is a weak force as compared to electromagnetic force. | It is a strong force as compared to gravitational force. |
Ques. Differentiate between strong nuclear force and weak nuclear force? (4 Marks)
Ans. Differences between strong and weak nuclear forces are:
| Strong nuclear force | Weak nuclear force |
|---|---|
| This force is responsible for the stability of nuclei. | The force is responsible for radioactive decay. |
| Range is 10-15m. | Range is of the order of 10-16m. |
| Played major role in holding nuclei together. | Played major role in nuclear reactions and radioactive decay. |
| Stronger force than weak nuclear force. | Weaker than strong nuclear force. |
Ques. Explain the law of conservation of energy and the law of conservation of charge? (2 Marks)
Ans. The law of conservation of energy and the law of conservation of charge are as follows:
- Law of Conservation of Energy: The Law of conservation of energy states that energy can neither be created nor destroyed. It can only be transformed from one form to another form. The total energy of an isolated system is constant.
- Law of Conservation of Charge: The Law of Conservation of Charge states that the total charge of an isolated system is constant throughout the system.
Ques. Explain the process of physics with respect to another field of science? (3 marks)
Ans. The relationship of physics with respect to other fields of science is as follows:
- Physics relationship with mathematics: Interpretation of different problems of mathematics, which includes differentiation, integration and differential equations, can be explained with the help of physics.
- Physics relationship with chemistry: The concept of physics is used in topics like x-ray, diffraction and radioactivity, which help distinguish between the various solids and help modify the periodic table.
- Physics's relationship with biology: The topics of physics, like pressure and its measurement, help study blood pressure and the functioning of the heart.
Ques. Determine the gravitational force if two masses are 20kg and 40kg separated by a distance 4m. G = 6.67259 x 10–11 N m2/kg2? (3 Marks)
Ans. Given:m1 = 20 kg, m2 = 40 kg
r = 4m and
G = 6.67259 x 10–11 N m2/kg2.
Universal gravitation formula is given by,
= [6.673×10–11 ×20×40] / 16
F = 333.65 x 10–11N
Ques. What are the subjects included in the macroscopic domain? (4 Marks)
Ans. The subjects included in the macroscopic domain are as follows:
- Mechanics: Mechanics is based on Newton's law of motion and the law of gravitation. Some common mechanics examples include water and sound waves and the propulsion of rockets when gas is ejected.
- Electrodynamics: Electrodynamics is based on the working of charged particles experiencing electrical and magnetic fields simultaneously. Some common examples of electrodynamics include the motion of a conductor in a magnetic field and the response of a circuit to the required AC voltage.
- Optics: Optics is a branch of physics that deals with light's behaviour and different properties. It includes interaction with different types of matter and the study of its instruments.
- Thermodynamics: Thermodynamics is based on the energy and how energy is utilised in the system. It also includes studies about the terms like temperature and entropy of a system. Measuring the efficiency of the heat engine is the most common example of thermodynamics.
Ques. Determine the gravitational force if two masses are 10kg and 20kg separated by a distance 2m. G = 6.67259 x 10–11 N m2/kg2. (3 Marks)
Ans. Given:m1 = 10 kg, m2 = 20 kg
r = 2m and
G = 6.67259 x 10–11 N m2/kg2.
Universal gravitation formula is given by,
= [6.673×10–11 ×10×20] / 4
F = 333.65 x 10–11N
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