Oscillations & Simple Harmonic Motion (SHM)

Phase 1 – Page 1 | IIT/JEE Solved Problems (Basic → Moderate)


Problem 1: Identifying SHM (Conceptual)

A particle moves along x-axis such that acceleration is given by a = −9x. Determine whether the motion is SHM and find its time period.

Solution:

Given:

a = −9x

Comparing with SHM equation:

a = −ω²x

⇒ ω² = 9 ⇒ ω = 3 rad/s

Time period:

T = 2π / ω = 2π / 3 s

IIT Thinking:
First identify SHM form → then extract ω.


Problem 2: Maximum Velocity in SHM

A particle executes SHM with amplitude 0.2 m and time period 2 s. Find its maximum velocity.

Solution:

ω = 2π / T = π rad/s

vmax = ωA = π × 0.2

vmax = 0.2π m/s


Problem 3: Displacement at Given Time

A particle executes SHM described by:

x = 0.1 sin(10t)

Find displacement at t = π/20 s.

Solution:

x = 0.1 sin(10 × π/20)

x = 0.1 sin(π/2) = 0.1 m


Problem 4: Energy Ratio in SHM

At what displacement does the kinetic energy become equal to potential energy?

Solution:

KE = PE

½mω²(A² − x²) = ½mω²x²

⇒ A² − x² = x²

⇒ x = A / √2

Answer: Displacement = A / √2


Problem 5: Time Period Change (Spring System)

The mass attached to a spring is increased four times. Find the new time period.

Solution:

T ∝ √m

If m → 4m:

T' = 2T


Problem 6: Simple Pendulum on Moon

If time period of a pendulum on Earth is 2 s, find its time period on Moon (gmoon = g/6).

Solution:

T ∝ 1 / √g

Tmoon = √6 × Tearth

Tmoon = 2√6 s


Problem 7: Velocity at Given Displacement

A particle executes SHM with amplitude A. Find velocity when displacement is x.

Solution:

v = ω√(A² − x²)

Velocity decreases as displacement increases.


Problem 8: Identifying Non-SHM

Which of the following motions is NOT SHM?

  • A) Projection of uniform circular motion
  • B) Simple pendulum (small angle)
  • C) Particle moving with constant speed in circle
  • D) Mass-spring system

Answer: C

IIT Trap:
Circular motion itself is NOT SHM — only its projection is.


Key Takeaways (Phase 1 – Page 1)

  • Always identify SHM equation first
  • Extract ω correctly
  • Use energy relations smartly
  • Avoid mixing f and ω

Phase 1 – Page 1 Completed Successfully ✅

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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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