Rankers Physics

Electric Potential Energy: Practice Problem & Solution

Assertion (A): Distance of closest approach for free target is more than that for fixed target. Reason (R): Total energy is conserved for free target but not for fixed target.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Electric Potential Energy. Understanding the underlying formula is key to arriving at the correct answer below:

For a free target, kinetic energy is shared, reducing the effective kinetic energy, leading to a larger closest approach distance (A is true). For a free target, mechanical energy of interacting particles is conserved. For a fixed target, external forces do work, so mechanical energy of the interacting particles is not conserved (R is true). This difference explains (A).

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