Physics · Gravitation · chapter 7 of 14

Class 11 Physics Chapter 7: Gravitation Assertion-reason questions with answers

2 assertion-reason questions on Gravitation, each with its answer and the reason, written from the NCERT chapter. For school exams on the CBSE pattern, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.

Question 1
Assertion (A): The total mechanical energy of a satellite in a circular orbit around the Earth is negative. Reason (R): Its potential energy is negative and twice the magnitude of its positive kinetic energy.
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Answer: (a) Both A and R are true, and R is the correct explanation of A.

K.E. = GmME/2r and P.E. = −GmME/r, so E = K.E. + P.E. = −GmME/2r, negative. R states exactly why the sum is negative, so R explains A.

Question 2
Assertion (A): An astronaut inside a satellite orbiting the Earth experiences weightlessness. Reason (R): The force of gravity is a conservative force.
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Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Both statements are true. The astronaut is weightless because the astronaut and the satellite are in free fall together; that gravity is conservative (work independent of path) has nothing to do with it, so R does not explain A.

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