Assertion (A) > : A man standing on a completely frictionless surface can propel himself by whistling. Reason (R) > : If no external force acts on a system, its momentum cannot change.

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Q: 103 (IAS/2000)

Assertion (A) : A man standing on a completely frictionless surface can propel himself by whistling.
Reason (R) : If no external force acts on a system, its momentum cannot change.

question_subject: 

Science

question_exam: 

IAS

stats: 

0,10,35,26,10,1,8

keywords: 

{'momentum': [0, 1, 0, 3], 'external force': [0, 0, 1, 0], 'frictionless surface': [0, 1, 0, 2]}

Option 1 suggests that both the assertion and reason are true, and that the reason correctly explains the assertion. However, although it appears that Reason accurately references Newton`s First Law or law of inertia, it doesn`t accurately explain the Assertion.

Option 2 is the correct answer because both Assertion and Reason are accurately referencing principles of physics, but Reason doesn`t explain Assertion correctly. A man can indeed propel himself by whistling on a frictionless surface because of the law of conservation of momentum (illustrated in Assertion) and Reason is also correct because it states Newton`s First Law of motion. However, the first law of motion isn`t the underlying principle that explains why the man can move when on a frictionless surface when he whistles.

Option 3 contradicts Newton`s First Law of Motion because it suggests that Reason is false.

Option 4 is incorrect because, although the explanation in Reason is correct, Assertion is also true because it is based on the principle of conservation of momentum. The man whistling would cause a reaction force that would push him forward on a frictionless surface.