## Class 11 - Physics - CHAPTER – 1 PHYSICAL WORLD (Q and A)

Q1: Who gave general theory of relativity?

Answer: Albert Einstein gave the general theory of relativity.

Q2: Is gravitational force is universal?

Answer: Yes, gravitational force is universal.

Q3: How a strong nuclear force is stronger comparing to electromagnetic force?

Answer: A strong nuclear force is 100 times stronger than the electromangnetic force in strength.

Q4: Is strong nuclear force change dependent?

Answer: Strong nuclear force is not charge dependent.

Q5: What is the range of weak nuclear force?

Answer: The range of weak nuclear force is of order of 10 -16 m.

Q6: Give an example of achievement in unification.

Answer: Unified celestial and terrestrial mechanics showed that the same laws of motion and the law of gravitational apply to both the domains.

Q7: Give an example of conversation law of energy.

Answer: A freely falling body under gravity is an example of conversation law of energy.

Q8: It is more important to have beauty in the equations of physics than to have them agree with experiments”. The great British physicst PAM Dirac held this view. Criticize this statement. Look out for some equations and results in this book which strike you as beautiful.

Answer: The statement of great British physicst PAM Dirac is partially true.
e.g., F = m✕a, E = mc² are some of the simple and beautiful equations of physics which have universal application.

However, this is not the case always. The equations involved in general theory of relatively and some of the latest work of higher physics are neither simple nor beautiful. They are rather difficult to understand.

Q9: Why do we express laws of physics in mathematical form?

Answer: The laws of physics are generally expressed as mathematical equations which are then used to make predictions about other phenomena. When a physics law is expressed in mathematical form, it is preferable to the qualitative statement. Moreover, mathematical form permits us to verify the various experimentally.