NCERT Solutions Class 11 Physics Chapter 1 – Physical World
NCERT Solutions for Class 11 Physics Chapter 1: Physical World
This introductory chapter explores the nature and scope of physics, fundamental forces in nature, and the scientific method. While primarily theoretical, understanding these concepts sets the foundation for studying physics.
Exercise Questions and Answers
Q1. Some of the most profound statements on the nature of science have come from Albert Einstein. Pick any one of his statements and discuss it.
Answer: Einstein’s statement: “The most incomprehensible thing about the world is that it is comprehensible.”
This profound statement highlights the remarkable fact that the universe, despite its vastness and complexity, follows orderly patterns and laws that the human mind can understand. Einstein marveled at how mathematical equations derived on paper can accurately describe physical phenomena billions of light-years away. This “comprehensibility” is the foundation of science – it assumes nature is rational and consistent, allowing us to discover universal laws through observation and reasoning.
Q2. “Every great physical theory starts as a heresy and ends as a dogma.” Give examples from the history of science.
Answer: Several examples illustrate this pattern:
- Heliocentric Theory: Copernicus’s idea that Earth revolves around the Sun was considered heresy by the Church. Today, it’s an established fact.
- Continental Drift: Wegener’s theory was ridiculed in the early 20th century. Now plate tectonics is fundamental geology.
- Quantum Mechanics: Initially considered bizarre and counterintuitive, it’s now the foundation of modern physics.
- Theory of Relativity: Einstein’s ideas were revolutionary and controversial. Now GPS satellites use relativistic corrections.
Q3. What are the fundamental forces in nature? State their relative strengths and range.
| Force | Relative Strength | Range | Examples |
|---|---|---|---|
| Strong Nuclear | 1 (strongest) | ~10⁻¹⁵ m | Binding nucleons |
| Electromagnetic | 10⁻² | Infinite | Light, chemical bonds |
| Weak Nuclear | 10⁻⁶ | ~10⁻¹⁸ m | Beta decay |
| Gravitational | 10⁻³⁹ (weakest) | Infinite | Planetary motion |
Q4. State the law of conservation of energy. What is its significance?
Answer: The law states: “Energy can neither be created nor destroyed; it can only be transformed from one form to another. The total energy of an isolated system remains constant.”
Significance:
- It’s a fundamental law applicable to all phenomena
- It helps analyze complex systems by tracking energy transformations
- It rules out perpetual motion machines
- It connects different branches of physics through energy equivalence
Key Takeaways
- Physics studies the fundamental laws governing natural phenomena
- Scientific method involves observation, hypothesis, experimentation, and theory
- Four fundamental forces govern all interactions in nature
- Conservation laws (energy, momentum, charge) are universal principles
- Physics has enabled technologies that transformed human civilization
- Unification of forces remains an active area of research
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