Which of the following scenarios best illustrates conservation of momentum?
A. Collision between two billiard balls on a frictionless table
B. A book resting on a table
C. A car accelerating on a straight road
D. A ball falling freely under gravity
Answer: Option A
Solution (By JKSSB Mock Tests)
Conservation of momentum applies to isolated systems with no external forces. In billiard ball collision on frictionless table, external forces (gravity, normal) cancel vertically, and no horizontal external forces act, so horizontal momentum is conserved. Book on table has zero momentum but no dynamic process. Falling ball has external gravity force. Accelerating car has external engine force. Thus only option B represents an isolated system where momentum conservation holds. Memory aid: Momentum conserved when net external force = 0. This conceptual question tests understanding of system boundaries and force analysis, crucial for mechanics sections in competitive exams.
Explanation:
A transformer operates on the principle of mutual induction. It consists of primary and secondary coils. When an alternating current flows through the primary coil, it generates a changing magnetic field. This fluctuating flux links with the secondary coil, inducing an alternating electromotive force (EMF) in it according to Faraday's Law.
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