Assertion and Reason on Spring Compression – Rankers Physics
Topic: Work Energy and Power
Subtopic: Potential Energy & Equilibrium

Assertion and Reason on Spring Compression

Given below are two statements:
Assertion (A): A block of mass \(m\) is dropped from a height \(h\) on to a spring of spring constant \(k\). The maximum compression \(x_{\text{max}}\) in the spring is given by \(x_{\text{max}} = \sqrt{\frac{2mgh}{k}}\)
Reason (R): The work done by gravitational force is equal to the elastic potential energy stored in the spring at maximum compression.
In the light of the above statements, choose the correct answer from the options given below.
Both (A) and (R) are true and (R) is the correct explanation of (A)
Both (A) and (R) are true but (R) is not the correct explanation of (A)
(A) is true but (R) is false
(A) is false but (R) is true

Solution:

By conservation of energy, the total loss in gravitational potential energy is \(mg(h + x_{\text{max}})\), which equals the elastic potential energy stored in the spring \(\frac{1}{2}kx_{\text{max}}^2\). Thus, the given formula for \(x_{\text{max}}\) is incorrect as it neglects the term \(mgx_{\text{max}}\). Hence, (A) is false but (R) is true.

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