JEE Advanced – Simple Harmonic Motion (SHM)

Tough Numerical Problems with Full Solutions – Page 3

Level: Advanced | Multi-step | Time-pressure oriented


Q16. SHM with Sudden Stop

A particle of mass m performs SHM with amplitude A. At displacement x = A/2, the particle is suddenly stopped. Find the new amplitude of motion.

Solution:

Velocity at x = A/2:

v² = ω²(A² − x²) = ω²(A² − A²/4) = (3/4)ω²A²

New energy = kinetic energy at that point:

½mω²A'² = ½m v² = ½m(3/4)ω²A²

⇒ A'² = 3A² / 4

Answer: A' = (√3 / 2) A

Trap: Do NOT reuse original amplitude after stopping.


Q17. SHM with Changing Force Constant

Spring constant is suddenly doubled when particle is at mean position. Find ratio of new amplitude to old amplitude.

Solution:

At mean position, velocity is maximum.

Initial energy:

E = ½kA²

New spring constant = 2k

½(2k)A'² = ½kA² ⇒ A' = A / √2

Answer: A' : A = 1 : √2


Q18. SHM on Smooth Incline

A block attached to spring oscillates on a smooth incline. Does angle of incline affect time period?

Solution:

Gravity component shifts equilibrium position only.

Time period depends on m and k only.

Answer: Time period is independent of angle

JEE Insight: Forces changing equilibrium ≠ restoring forces


Q19. Maximum Jerk in SHM

Find position where jerk is maximum.

Solution:

Jerk = da/dt = −ω²v

|jerk| ∝ |v|

Velocity is maximum at mean position.

Answer: Mean position


Q20. Phase Difference & Energy Ratio

Two particles have same SHM but phase difference π/3. Find ratio of their potential energies when one is at mean position.

Solution:

At mean position, PE₁ = 0

For second particle:

x = A sin(π/3) = (√3/2)A

PE₂ = ½k x² = 3/4 (½kA²)

Answer: 0 : 3/4


Q21. SHM with Damping (Conceptual)

If damping force is introduced, which quantity remains constant?

  • Amplitude ❌
  • Energy ❌
  • Frequency (approximately) ✅
  • Phase ❌

Answer: Frequency (for light damping)


Q22. Velocity Distribution

At what fraction of amplitude does velocity become half of maximum?

Solution:

v = ω√(A² − x²) = vmax/2

⇒ A² − x² = A²/4 ⇒ x = (√3/2)A

Answer: x = (√3/2)A


Why Page 3 Is Rank-Deciding

  • Combines sudden change + energy logic
  • Tests understanding beyond formulas
  • Matches hardest JEE Advanced numericals
  • Builds calmness for lengthy questions

JEE Advanced SHM – Page 3 Completed

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🔹 Simple Harmonic Motion (SHM) — Core Series

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🔹 Simple Harmonic Motion (SHM) — Extended Series (30–56)

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