Physical World Class 11 Notes Physics| Important Question Chapter 1

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Physical World Class 11 Notes

Fundamental Forces in Nature

There are four fundamental forces in Nature:

  1. Gravitational Force
  2. Electromagnetic Force
  3. Strong Nuclear Force
  4. Weak Nuclear Force

1.Gravitational Force: It is the force of mutual attraction between two bodies by virtue of their masses.

Some important properties of Gravitational force are:

a) It is a universal attractive force.

b) It obeys the inverse square law. ( Force ∝ 1/r2)

c) It is the long-range force and does not need any intervening medium.

d) It is the weakest known force in nature.

Example: a) All objects on the earth experience the force of gravity due to the earth.

b) Gravity governs the motion of the moon of the planet around the earth and motion of the planet around the sun.

c) It plays a key role in the large-scale phenomenon such as the formation and evolution of stars, galaxies etc.

2.Electromagnetic Force: The electromagnetic force acts between charge particles and is the combination of all electrical and magnetic forces.

Some Important Properties are:

a) It may be attractive or repulsive.

b) It obeys the inverse square law. ( F∝ 1/r2)

c) It is the long-range force and does not require any intervening medium.

d) It is 1036 times stronger than the gravitational force.

Ex: Force of friction, an Elastic force of a string etc.

3. Strong Nuclear Force: The force which binds together the protons and neutrons in a nucleus is called strong nuclear force. This force is responsible for the stability of the nucleus.

Some important properties are:

a) It is the strongest of all the fundamental forces, about 100 times the electromagnetic force and 1038 times the gravitational force in strength.

b) It is charge independent.

Its range is extremely small, about nuclear dimensions( 10-15m)

4. Weak Nuclear Force: The weak nuclear Force appears only in certain nuclear processes such as the β-decay of a nucleus.

In β-Decay, the nucleus emits an electron and an uncharged particle called neutrino.

Some important properties:

a) The weak nuclear force is about 1025 times stronger than gravitational force but much weaker than the electromagnetic forces.

b) The range of the weak nuclear force is exceeding small, of the order of 10-16 m.

Clearly,

Fg: Fw: Fe: Fn: 1: 1025: 1036: 1038

Physical world class 11 notes physics

Physical world class 11 notes physics

Q1. Name the strongest fundamental force in Nature.

Ans: The strongest fundamental force in nature is “strong nuclear force”.

Q2. Name the weakest Nuclear Force in Nature.

Ans: The weakest nuclear force in nature is “gravitational force”.

Q3. What is the range of electromagnetic force?

Ans: The range of electromagnetic force is 10-28 meters.

Q4. Name the fundamental force which has the shortest range.

Ans: Weak Nuclear Force has the shortest range among the fundamental force.

Q5. Arrange the four fundamental forces in the increasing order of their strength.

Ans: Fg: Fw: Fe: Fn: 1: 1025: 1036: 1038

You can Also see: Class 11 Physics Vector Notes

Dimensional Analysis Question and Answer

Physical world notes class 11 physics

Physical world notes class 11 physics

 

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