Problem Solving Simple Harmonic Motion

Concepts to remember on Problem-Solving Simple Harmonic Motion for JEE and CBSE board exams:

Simple Harmonic Motion (SHM):

  • Periodic motion where the restoring force is directly proportional to the negative displacement.
  • Examples: Pendulum, spring-mass system, and oscillating bodies.
  • Motion takes place along a straight line.

Characteristics of SHM:

  • Displacement (x): A sinusoidal function of time (t) with amplitude (A) and angular frequency (ω).

  • x(t) = A cos(ωt + Φ) or x(t) = A sin(ωt + Φ)

  • Velocity (v): Also sinusoidal, 90° out of phase with displacement.

  • v(t) = -ωA sin(ωt + Φ) or v(t) = ωA cos(ωt + Φ)

  • Acceleration (a): Sinusoidal, 180° out of phase with displacement and proportional to (-Aω²).

  • a(t) = -ω²A cos(ωt + Φ) or a(t) = -ω²A sin(ωt + Φ)

Equations of SHM:

  • Displacement: x = A cos(ωt + ∅), where ∅ is the phase constant.
  • Velocity: v = -Aω sin(ωt + ∅).
  • Acceleration: a = -Aω² cos(ωt + ∅).

Time Period (T):

  • Time taken for one complete oscillation.
  • T = 2π√(m/k), where m is the mass of the oscillating object, and k is the spring constant.

Frequency (f):

  • Number of oscillations per second.
  • f = 1/T = ω/2π.

Angular Frequency (ω):

  • Measures the rate of change of phase angle.
  • ω = 2πf = √(k/m).

Phase:

  • Describes the position of an oscillating particle within its cycle.
  • Phase difference: Describes the difference in phase between two oscillations.

Energy in SHM:

  • Total energy (E) is constant and the sum of kinetic energy (K) and potential energy (U).
  • K = ½kA², and U = ½kA² cos²(ωt + ∅).
  • E = ½kA².

Resonance:

  • Occurs when the frequency of an applied periodic force matches the natural frequency of the system.
  • Causes maximum amplitude and energy transfer.


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