Instructions
Total Questions: 20 | Marks: 4 each | No Negative Marking
Simple Harmonic Motion (SHM) & Oscillations – IIT JEE Notes (Set 10)
Simple Harmonic Motion (SHM)
Definition
Simple Harmonic Motion is a type of periodic motion in which the restoring force is directly proportional to displacement and acts towards the mean position.
Restoring Force
F = -kx
The negative sign indicates that the force is always directed towards the equilibrium position.
Basic Equations of SHM
Displacement
x = A sin(ωt + φ)
Velocity
v = ω√(A² – x²)
Acceleration
a = -ω²x
Time Period and Frequency
Time Period
T = 2π/ω
Frequency
f = 1/T
Angular Frequency
ω = 2πf
Energy in SHM
Total Energy
E = (1/2)kA²
Total energy remains constant throughout the motion.
Kinetic Energy
Maximum at mean position and zero at extreme positions.
Potential Energy
Maximum at extreme positions and minimum at mean position.
Important Positions in SHM
Mean Position
Displacement = 0, velocity is maximum, acceleration is zero.
Extreme Position
Displacement = maximum, velocity is zero, acceleration is maximum.
Spring-Mass System
Time Period
T = 2π√(m/k)
Key Insight
Time period depends on mass and spring constant, not on amplitude.
Simple Pendulum
Time Period
T = 2π√(l/g)
Important Point
Valid only for small oscillations.
Phase and Phase Difference
Phase
Represents the state of oscillation at any instant.
Unit
Radian
Phase Difference
Difference in phase between two oscillating particles.
Graphical Representation
Displacement-Time Graph
Sinusoidal curve.
Velocity-Time Graph
Also sinusoidal but shifted by π/2.
Acceleration-Time Graph
Opposite phase to displacement.
Characteristics of SHM
Periodic Motion
Motion repeats after equal time intervals.
Oscillatory Nature
Motion occurs about a fixed mean position.
Important Relationships
Maximum Velocity
vₘₐₓ = ωA
Maximum Acceleration
aₘₐₓ = ω²A
Energy Relation
Total energy ∝ Amplitude²
Conceptual Insights
Key Understanding
Velocity and acceleration are not constant. Both vary continuously during motion.
Common Mistakes
Students often assume acceleration is maximum at mean position, which is incorrect.
Important Exam Concepts
Conceptual Traps
Time period of SHM does not depend on amplitude. Frequency remains constant for given system.
JEE Strategy
Focus on formulas, graphs, and understanding relation between displacement, velocity, and acceleration.
