Class 11 Physics Chapter 1 – Physical
World, Units & Measurements: The
Definitive 400 Q&A Study Vault with
Detailed Rationale. Covering
Fundamental Forces, Conservation
Laws, SI Base & Derived Units,
Dimensional Analysis of 100+
Quantities, Least Count & Zero Errors,
Significant Figure Rules, Propagation
of Percentage Errors, Parallax &
Astronomical Units, and Full
Numerical Conversions – Perfect for
CBSE, JEE Foundation, and State
Board Exams.
Q1. What is the origin of the word "Physics"?
Ans: Greek word "Phusikḗ" meaning nature.
Rationale: The term reflects physics as the study of nature and natural
phenomena.
,Q2. Who is known as the father of modern physics?
Ans: Albert Einstein (though Galileo is often called the father of modern
science).
Rationale: Einstein revolutionized physics with relativity and quantum
concepts, but Galileo pioneered the scientific method.
Q3. Define Science.
Ans: A systematic enterprise that builds and organizes knowledge in the
form of testable explanations and predictions about the universe.
Rationale: It relies on observation, experimentation, and logical reasoning.
Q4. What are the two principal thrusts in physics?
Ans: Unification and Reduction.
Rationale: Unification finds common laws; reduction breaks complex
systems into simpler components.
Q5. Give an example of unification in physics.
Ans: Newton's law of gravitation unifying celestial and terrestrial motion.
Rationale: It applies equally to falling apples and orbiting planets.
Q6. Give an example of reduction in physics.
Ans: Explaining gas pressure through molecular kinetic energy.
Rationale: Macroscopic properties are derived from microscopic particle
behavior.
Q7. Name the four fundamental forces in nature.
Ans: Gravitational, Electromagnetic, Strong Nuclear, Weak Nuclear.
Rationale: All interactions in the universe arise from these four forces.
Q8. Which is the weakest fundamental force?
Ans: Gravitational force.
Rationale: It is 10³⁶ times weaker than the strong nuclear force.
,Q9. Which is the strongest fundamental force?
Ans: Strong nuclear force.
Rationale: It holds protons and neutrons together in the nucleus against
electrostatic repulsion.
Q10. Which force is responsible for radioactive decay?
Ans: Weak nuclear force.
Rationale: It governs beta decay and neutrino interactions.
Q11. Which force acts between charged particles?
Ans: Electromagnetic force.
Rationale: It includes both electric and magnetic interactions.
Q12. What is the range of the strong nuclear force?
Ans: Short range, about 10⁻¹⁵ m (nuclear dimensions).
Rationale: It does not act beyond the nucleus.
Q13. What is the range of gravitational force?
Ans: Infinite range.
Rationale: It acts over astronomical distances.
Q14. What is the range of electromagnetic force?
Ans: Infinite range.
Rationale: It decreases as 1/r² but never becomes zero.
Q15. What is the range of weak nuclear force?
Ans: Extremely short, about 10⁻¹⁸ m.
Rationale: It operates only at subnuclear distances.
Q16. State the Law of Conservation of Energy.
Ans: Energy can neither be created nor destroyed; it can only change form.
Rationale: Total energy of an isolated system remains constant.
, Q17. State the Law of Conservation of Linear Momentum.
Ans: Total momentum of a system remains constant if no external force
acts.
Rationale: Derived from Newton's second and third laws.
Q18. State the Law of Conservation of Angular Momentum.
Ans: Total angular momentum remains constant if no external torque acts.
Rationale: Examples include a spinning ice skater pulling arms in.
Q19. State the Law of Conservation of Electric Charge.
Ans: Net charge in an isolated system remains constant.
Rationale: Charge can be transferred but not created or destroyed.
Q20. State the Law of Conservation of Mass.
Ans: Mass is neither created nor destroyed in a chemical reaction.
Rationale: In nuclear reactions, mass converts to energy (E=mc²), so it's not
absolute.
Q21. Which conservation law is linked to the symmetry of time?
Ans: Conservation of Energy.
Rationale: Energy conservation arises because physical laws do not change
with time.
Q22. Which conservation law is linked to the symmetry of space?
Ans: Conservation of Linear Momentum.
Rationale: Momentum conservation arises because physical laws are the
same everywhere.
Q23. Which conservation law is linked to rotational symmetry?
Ans: Conservation of Angular Momentum.
Rationale: It arises because laws are the same in all directions.
World, Units & Measurements: The
Definitive 400 Q&A Study Vault with
Detailed Rationale. Covering
Fundamental Forces, Conservation
Laws, SI Base & Derived Units,
Dimensional Analysis of 100+
Quantities, Least Count & Zero Errors,
Significant Figure Rules, Propagation
of Percentage Errors, Parallax &
Astronomical Units, and Full
Numerical Conversions – Perfect for
CBSE, JEE Foundation, and State
Board Exams.
Q1. What is the origin of the word "Physics"?
Ans: Greek word "Phusikḗ" meaning nature.
Rationale: The term reflects physics as the study of nature and natural
phenomena.
,Q2. Who is known as the father of modern physics?
Ans: Albert Einstein (though Galileo is often called the father of modern
science).
Rationale: Einstein revolutionized physics with relativity and quantum
concepts, but Galileo pioneered the scientific method.
Q3. Define Science.
Ans: A systematic enterprise that builds and organizes knowledge in the
form of testable explanations and predictions about the universe.
Rationale: It relies on observation, experimentation, and logical reasoning.
Q4. What are the two principal thrusts in physics?
Ans: Unification and Reduction.
Rationale: Unification finds common laws; reduction breaks complex
systems into simpler components.
Q5. Give an example of unification in physics.
Ans: Newton's law of gravitation unifying celestial and terrestrial motion.
Rationale: It applies equally to falling apples and orbiting planets.
Q6. Give an example of reduction in physics.
Ans: Explaining gas pressure through molecular kinetic energy.
Rationale: Macroscopic properties are derived from microscopic particle
behavior.
Q7. Name the four fundamental forces in nature.
Ans: Gravitational, Electromagnetic, Strong Nuclear, Weak Nuclear.
Rationale: All interactions in the universe arise from these four forces.
Q8. Which is the weakest fundamental force?
Ans: Gravitational force.
Rationale: It is 10³⁶ times weaker than the strong nuclear force.
,Q9. Which is the strongest fundamental force?
Ans: Strong nuclear force.
Rationale: It holds protons and neutrons together in the nucleus against
electrostatic repulsion.
Q10. Which force is responsible for radioactive decay?
Ans: Weak nuclear force.
Rationale: It governs beta decay and neutrino interactions.
Q11. Which force acts between charged particles?
Ans: Electromagnetic force.
Rationale: It includes both electric and magnetic interactions.
Q12. What is the range of the strong nuclear force?
Ans: Short range, about 10⁻¹⁵ m (nuclear dimensions).
Rationale: It does not act beyond the nucleus.
Q13. What is the range of gravitational force?
Ans: Infinite range.
Rationale: It acts over astronomical distances.
Q14. What is the range of electromagnetic force?
Ans: Infinite range.
Rationale: It decreases as 1/r² but never becomes zero.
Q15. What is the range of weak nuclear force?
Ans: Extremely short, about 10⁻¹⁸ m.
Rationale: It operates only at subnuclear distances.
Q16. State the Law of Conservation of Energy.
Ans: Energy can neither be created nor destroyed; it can only change form.
Rationale: Total energy of an isolated system remains constant.
, Q17. State the Law of Conservation of Linear Momentum.
Ans: Total momentum of a system remains constant if no external force
acts.
Rationale: Derived from Newton's second and third laws.
Q18. State the Law of Conservation of Angular Momentum.
Ans: Total angular momentum remains constant if no external torque acts.
Rationale: Examples include a spinning ice skater pulling arms in.
Q19. State the Law of Conservation of Electric Charge.
Ans: Net charge in an isolated system remains constant.
Rationale: Charge can be transferred but not created or destroyed.
Q20. State the Law of Conservation of Mass.
Ans: Mass is neither created nor destroyed in a chemical reaction.
Rationale: In nuclear reactions, mass converts to energy (E=mc²), so it's not
absolute.
Q21. Which conservation law is linked to the symmetry of time?
Ans: Conservation of Energy.
Rationale: Energy conservation arises because physical laws do not change
with time.
Q22. Which conservation law is linked to the symmetry of space?
Ans: Conservation of Linear Momentum.
Rationale: Momentum conservation arises because physical laws are the
same everywhere.
Q23. Which conservation law is linked to rotational symmetry?
Ans: Conservation of Angular Momentum.
Rationale: It arises because laws are the same in all directions.
