MCQEasyJEE 2023Energy in SHM

JEE Physics 2023 Question with Solution

The variation of kinetic energy (KEKE) of a particle executing simple harmonic motion with the displacement (xx) starting from mean position to extreme position (AA) is given by:

  • A

    Parabola

  • B

    Straight line

  • C

    Kinetic energy and displacement are inversely proportional

  • D

    Sine curve

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: A particle executes simple harmonic motion, and we need the variation of kinetic energy (KEKE) with displacement xx from the mean position to the extreme position.

Find: The nature of the graph between KEKE and xx.

In simple harmonic motion, total mechanical energy remains constant, and kinetic energy depends on displacement.

KE=EPEKE = E - PE

Also, the potential energy in simple harmonic motion varies as:

PE=12kx2PE = \frac{1}{2}kx^2

Hence, kinetic energy varies with the square of displacement, so the KEKE versus xx graph is parabolic.

Therefore, the correct option is A.

Explanation from Energy Relation

Given: The particle is in simple harmonic motion.

Find: The shape of the graph of KEKE versus xx.

From the extracted solution, kinetic energy is related to displacement through the energy expression. Since the displacement term appears as x2x^2, the dependence is quadratic.

A quadratic dependence of a quantity on displacement gives a parabola when plotted against xx.

Therefore, the graph is a parabola, so the correct option is A.

Common mistakes

  • Assuming KEKE is directly proportional to xx and choosing a straight line is incorrect because energy in simple harmonic motion depends on the square of displacement. Use the quadratic dependence to identify the graph shape.

  • Confusing the displacement-time graph of simple harmonic motion with the KEKE-displacement graph is incorrect. A sine curve describes variation with time, not with displacement in this case.

  • Interpreting 'inversely proportional' from the fact that KEKE decreases as xx increases is incorrect. Decreasing does not imply inverse proportionality; the actual relation is quadratic.

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