The amplitude of the vibrating particle due to superposition of two SHMs
$$x_1=\ 2\ Sin\left(\omega t\right)$$ and
$$x_2=\ 2\ Sin\left(\omega t+\ \frac{2\pi}{3}\right)$$ .
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Simple Harmonic Motion (SHM) is one of the most important and widely tested chapters in JEE Physics. It describes the rhythmic oscillatory behaviour found in springs, pendulums, and countless physical systems, and it forms the conceptual bridge between mechanics and waves. Because the chapter is rich in both formula-based and reasoning-based questions, JEE Simple Harmonic Motion questions appear reliably in JEE Main and JEE Advanced and reward students who understand the underlying restoring-force principle thoroughly. This chapter covers the definition and conditions for SHM, the equations of displacement, velocity, and acceleration as functions of time, energy in SHM, the simple pendulum and spring-mass system, superposition of SHMs, and damped and forced oscillations. JEE Main typically tests time-period formulas, energy, and the phase relationships between displacement, velocity, and acceleration. JEE Advanced often presents more involved problems combining SHM with energy methods, constraints, or the superposition of two oscillations. Practising topic-wise JEE Questions helps you develop fluency with the sinusoidal equations and apply energy methods to oscillation problems with confidence.
The amplitude of the vibrating particle due to superposition of two SHMs
$$x_1=\ 2\ Sin\left(\omega t\right)$$ and
$$x_2=\ 2\ Sin\left(\omega t+\ \frac{2\pi}{3}\right)$$ .
The resultant amplitude of two SHMs having amplitudes $$A_1$$ and $$A_2$$ with phase difference $$\phi$$ is
$$A=\sqrt{A_1^2+A_2^2+2A_1A_2\cos\phi}$$
Here,
$$A_1=A_2=2,\qquad \phi=\frac{2\pi}{3}$$
Therefore, $$A=\sqrt{2^2+2^2+2(2)(2)\cos\frac{2\pi}{3}}$$
$$A=\sqrt{4+4+8\left(-\frac{1}{2}\right)}$$
$$A=\sqrt{4}=2$$
Therefore, $${A=2}$$
Hence, the correct option is B.
Parameter | Details |
|---|---|
Topic Name | Simple Harmonic Motion (SHM) |
Subject | Physics |
JEE Main Weightage | ~3-5% (1-2 questions on average) |
JEE Advanced Weightage | ~4-6% (often in combined problems) |
Difficulty Level | Moderate |
Important Concepts | SHM Equations, Energy, Simple Pendulum, Spring Systems, Superposition |
Recommended Practice Level | High - attempt 70+ mixed problems |
Concept | Importance | Difficulty Level | Frequently Asked In |
|---|---|---|---|
SHM Definition and Restoring Force | Very High | Easy-Moderate | JEE Main |
Displacement, Velocity and Acceleration Equations | Very High | Moderate | JEE Main and Advanced |
Phase Relationships | High | Moderate | JEE Main and Advanced |
Energy in SHM | Very High | Moderate | JEE Main and Advanced |
Simple Pendulum and Time Period | Very High | Moderate | JEE Main |
Spring-Mass Systems | Very High | Moderate | JEE Main and Advanced |
Superposition of SHMs | High | Moderate-High | JEE Advanced |
Damped and Forced Oscillations | Moderate | Moderate | JEE Main |
Concept learning: Begin by understanding the restoring force condition as the defining property of SHM, then derive or internalise the sinusoidal equations for displacement, velocity, and acceleration. Understand the phase relationships between these quantities carefully, noting that velocity leads displacement by 90 degrees and acceleration opposes displacement.
Formula revision: Keep the time-period expressions for the pendulum and spring systems, the energy equations for kinetic and potential components, and the superposition result for two SHMs together for quick review. Structured JEE Online Coaching helps you reinforce SHM derivations, clear doubts on spring-combination problems, and build problem-solving confidence efficiently.
Problem-solving techniques: For energy questions, use the total energy as a constant and switch freely between the kinetic and potential forms. For spring combinations, compute the effective spring constant using the series or parallel formula before applying the time-period expression. For pendulum problems, ensure the amplitude is small before applying the standard formula.
Common mistakes: Forgetting that acceleration and displacement point in opposite directions, confusing series and parallel spring combinations, applying the simple-pendulum formula to large-amplitude oscillations, and sign errors in phase calculations.
Exam strategy: Solve direct time-period and energy questions first, then tackle superposition and combined SHM-and-mechanics problems that need more steps. When a problem involves a spring-and-block system, find the equilibrium position first, then set up SHM about it.
Exam | Average Questions | Expected Marks |
|---|---|---|
JEE Main | 1-2 | 4-8 |
JEE Advanced | 1-2 (often combined) | 4-10 |
SHM is a steady contributor in JEE Main through time-period, energy, and phase questions. In JEE Advanced, it frequently appears within combined mechanics problems that test energy conservation and constraint analysis across an oscillating system.
Reinforcing these techniques in timed conditions with a JEE Mock Test builds the speed and phase-reasoning ability that SHM questions reward.
JEE Simple Harmonic Motion (SHM) questions test concepts such as SHM equations, restoring force, energy in SHM, phase relationships, spring-mass systems, simple pendulums, and superposition of oscillations. These topics are commonly asked in both JEE Main and JEE Advanced.
Yes. Simple Harmonic Motion is an important Mechanics chapter and typically contributes 1–2 questions in JEE Main every year.
Energy in SHM, time periods of spring-mass systems, simple pendulums, phase relationships, angular frequency, and spring combinations are the most frequently tested topics.
SHM is generally considered moderately difficult because it requires a strong understanding of periodic motion, energy conservation, and oscillatory systems.
JEE Main usually includes 1–2 questions from SHM, while JEE Advanced often asks 1–2 questions involving energy methods, spring systems, or combined oscillation concepts.
To prepare effectively, solve previous year JEE questions, practise spring-combination and pendulum problems, revise important formulas, and attempt timed mock tests regularly
Students often confuse spring combinations, make sign errors while applying restoring force and acceleration equations, and incorrectly use the simple pendulum formula for large amplitudes.
Key formulas include SHM displacement, velocity and acceleration equations, angular frequency relations, time-period formulas for springs and pendulums, energy equations, and phase relationship expressions.
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