Physics · Properties of bulk matter · chapter 8 of 14

Class 11 Physics Chapter 8: Mechanical Properties of Solids Assertion-reason questions with answers

2 assertion-reason questions on Mechanical Properties of Solids, 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): Steel is more elastic than rubber. Reason (R): For the same stress, steel undergoes a far smaller strain than rubber, because its Young's modulus is much larger.
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Answer: (a) Both A and R are true, and R is the correct explanation of A.

Both are true. In physics the material that stretches less for a given load is the more elastic one, and steel's large Young's modulus is exactly why it strains less; so R explains A.

Question 2
Assertion (A): Young's modulus and shear modulus are not defined for a liquid. Reason (R): The bulk modulus of a liquid is much smaller than that of a solid.
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Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Both are true. But Y and G are undefined for a liquid because a liquid has no definite length or shape, not because its bulk modulus is small; so R does not explain A.

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