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NEET Physics · Oscillations and Waves

Energy in SHM and oscillations of a spring

Taught in NCERT Class 11 Physics, Chapter 13: Oscillations.

2 verified questions: Easy 0 · Medium 1 · NEET level 1

Sample questions

Sample 1Medium

A graph for a block oscillating on a spring in SHM has displacement x on the horizontal axis, from −A to +A. Two parabolas are drawn: potential energy, zero at x = 0 and maximum at ±A, and kinetic energy, maximum at x = 0 and zero at ±A. A horizontal line marks the total energy E. At x = A/2, what fraction of E is kinetic energy?

  1. A

    1/2

  2. B

    1/4

  3. C

    3/4

  4. D

    1/3

Show the answer
The answer is C.

Potential energy = ½kx² = ¼ × ½kA² = E/4 at x = A/2. Since the total energy is constant, KE = E − E/4 = 3E/4.

  • A.

    The two energies are equal at x = A/√2, not A/2.

  • B.

    1/4 is the potential energy fraction at A/2.

  • D.

    1/3 does not follow from ½kx² at x = A/2.

NCERT: Class 11 Physics, Chapter 13

Sample 2NEET level

A block of mass 0.5 kg attached to a spring of force constant 200 N/m oscillates on a smooth horizontal surface with an amplitude of 0.1 m. The maximum speed of the block is

  1. A

    1.41 m/s

  2. B

    2 m/s

  3. C

    2.83 m/s

  4. D

    40 m/s

Show the answer
The answer is B.

ω = √(k/m) = √(200/0.5) = 20 rad/s, so v_max = ωA = 20 × 0.1 = 2 m/s. Check by energy: ½kA² = 1 J = ½mv_max² gives v_max = 2 m/s.

  • A.

    Equates ½kA² to mv² instead of ½mv².

  • C.

    Equates kA² to ½mv², dropping the ½ on the spring's side.

  • D.

    Takes ω = k/m = 400 rad/s, forgetting the square root.

NCERT: Class 11 Physics, Chapter 13 (Oscillations), Energy in simple harmonic motion

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