Q.The displacement–time curve of a particle executing S.H.M. is a smooth sinusoid of period 4 s. The displacement is positive and near its maximum at t=0 s, falls to zero at about t=1 s, reaches its most negative value at about t=2 s, returns to zero at about t=3 s, and rises back to its positive maximum at t=4 s; this 4-second cycle then repeats up to t=7 s. Choose the correct statement(s). (Note: more than one of the given options may be correct.)
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Simple Harmonic Motion
Simple Harmonic Motion: The Natural Rhythm of Things
Imagine a ball placed at the bottom of a perfectly smooth, U-shaped bowl. If you give it a gentle push, what happens? It rolls up one side, slows down, stops for an instant, then rolls back down, past the bottom, up the other side, stops, and returns. Left alone, it keeps doing this — back and forth, back and forth — in a steady, repeating rhythm.
That rhythm is the heart of Simple Harmonic Motion (SHM). It's the most fundamental kind of oscillatory (back-and-forth) motion in physics.
The Intuition: A Restoring Force That Fights Displacement
The key idea is this: the further you push the object from its resting (equilibrium) position, the stronger the force that tries to pull it back.
In the bowl, when the ball is at the bottom (equilibrium), gravity pulls straight down, and the bowl pushes straight up — no sideways force. But when you push the ball up the side, gravity now has a component that pulls it down the slope. The higher up the side you push it, the steeper the slope, and the stronger that pull-back force becomes.
This is a restoring force — it always points toward equilibrium. And crucially, in SHM, this restoring force is directly proportional to the displacement from equilibrium. Double the displacement, double the restoring force.
F=−kx
- F is the restoring force.
- x is the displacement from equilibrium.
- k is a positive constant (the "stiffness" of the system).
- The minus sign is crucial: it tells you the force is opposite to the displacement.
The Precise Statement
Simple Harmonic Motion is the motion of an object where the restoring force is directly proportional to the displacement from equilibrium and acts in the opposite direction.
That's it. That single condition — F=−kx — is the entire definition. Everything else (the sine waves, the formulas for period and frequency) follows mathematically from this one law.
What Does This Motion Look Like?
If you track the ball's position over time, you get a beautiful, smooth wave — a sine wave (or cosine wave). It's the same shape as the shadow of a spinning wheel cast on a wall.
The motion has three key descriptors:
- Amplitude (A): The maximum displacement from equilibrium. How far you initially pushed the ball up the side of the bowl.
- Period (T): The time it takes to complete one full back-and-forth cycle (e.g., from the leftmost point, back to the leftmost point).
- Frequency (f): How many cycles happen per second. f=1/T.
A remarkable fact: for a given system (fixed k and fixed mass m), the period and frequency do not depend on the amplitude. A big push and a tiny push take exactly the same time to complete one cycle. This is called isochronism — and it's why pendulums were used to keep time in clocks.
The Mathematical Description (Derived from F=−kx)
Using Newton's second law (F=ma) and the definition of acceleration (a=dt2d2x), the condition F=−kx becomes:
mdt2d2x=−kx
This is a differential equation. Its solution — the position as a function of time — is:
x(t)=Acos(ωt+ϕ)
Where:
- ω=mk is the angular frequency (radians per second). It tells you how fast the oscillation is.
- ϕ is the phase constant (determines where in the cycle you start measuring time). …
Two instants have the same phase only if they are separated by a whole number of periods. Here T=4 s, so the phase repeats every 4 s. Pairs t=2,6 (option B) and t=1,5 (option D) differ by 4 s=T — same …
Same phase means same displacement and same direction of motion, which recurs exactly one full period later. Reading the period as T=4 s, only time separations equal to 4 s (or any multiple) give the same phase. That is true for the pair 2 s,6 s and the pair 1 s,5 s.
Concept: phase repeats every period
The phase of an SHM advances by 2π each period. Two instants t1,t2 are in phase iff
t2−t1=nT,n=0,1,2,…
If the separation is an odd multiple of T/2, the states are in anti-phase (equal and opposite).
Read the period
The curve completes one full oscillation in 4 s, so T=4 s.
Test each option
- (A) t=0,2: Δt=2 s=T/2 ⇒ anti-phase, not same. False. …
Step 1: Read the period directly off the curve: one full cycle takes T=4 s.
Step 2: Two instants are in the same phase iff they are separated by a whole number of periods, Δt=nT; if Δt is an odd multiple of T/2, they are in anti-phase (equal magnitude, opposite sign/direction), not the same phase.
Step 3: Test each pair: (a) t=0,2: Δt=2 s=T/2 — anti-phase, not same. …
Showing the 12 most recent of 96 on this concept.
- AP EAPCET 2026Set eng-2026-05-12-AN1 markMCQQ.In SHM, velocity leads displacement by (A) 0 (B) 90° (C) 180° (D) 45°
›Reveal solutionSolution
Differentiating the SHM displacement gives velocity as a cosine of the same phase, which is exactly a sine shifted forward by 90∘ — velocity leads displacement by 90∘.
Concept and Intuition
In SHM, displacement, velocity, and acceleration are all sinusoidal with the same angular frequency ω, but shifted in phase relative to each other because velocity is the time-derivative of displacement (and acceleration the derivative of velocity). Each derivative operation on a sinusoid produces a 90∘ phase shift.
Step-by-Step Solution
- Let displacement be x=Asin(ωt).
- Velocity: v=dtdx=Aωcos(ωt).
- Rewrite cosine as a phase-shifted sine: cos(ωt)=sin(ωt+90∘).
- So v=Aωsin(ωt+90∘) — this is displacement's waveform shifted ahead by 90∘, i.e. velocity leads displacement by 90∘. …
- AP EAPCET 2026Set eng-2026-05-12-AN1 markMCQQ.The figure corresponds to circular motion where the radius of the circle, the period of revolution, the initial position and sense of revolution (ie clockwise or anti-clockwise) are indicated. The corresponding simple harmonic motion of the x-projection of the radius vector of the revolving particle p is (Figure: a circle of radius 3 m centred at the origin of the x-y plane. The particle p starts at t = 0 at the leftmost point of the circle, i.e. on the negative x-axis. The period of revolution is T = 2 s. The sense of revolution is clockwise, as indicated by an arrow at the bottom of the circle.) (A) x=3sinπt (B) x=−3sinπt (C) x=−3cosπt (D) x=2sin(32π)t
›Reveal solutionSolution
The x-projection of uniform circular motion is SHM with the same ω as the rotation; starting at an extreme point of the projection fixes it as a (negative) cosine, giving x=−3cos(πt).
Concept and Intuition
When a particle moves uniformly on a circle of radius A, the projection of its position vector on any diameter executes SHM with amplitude A and the same angular frequency ω as the circular motion. The phase of that SHM is fixed entirely by where the particle starts and how fast its projection is changing there — nothing more is needed once you know the starting point is a turning point (extremum) or a zero-crossing of the projection.
Step-by-Step Solution
- Angular frequency: ω=T2π=2s2π=π rad/s.
- Amplitude of the x-projection equals the radius: A=3 m.
- At t=0 the particle p is at the leftmost point of the circle, so its position is (−3,0), i.e. x(0)=−3 m=−A.
- At the leftmost/rightmost points of a circle, the velocity of the particle is purely tangential, i.e. purely along y; the instantaneous rate of change of x is zero there. So x=0 point is a turning point of the SHM (like the extreme ends of a spring's oscillation), not a point where x passes through zero.
- A general SHM projection is x(t)=Acos(ωt+ϕ). Turning points of cos occur at t=0 automatically when ϕ=0 or π; we need x(0)=−A, so cosϕ=−1⇒ϕ=π.
- Hence x(t)=Acos(ωt+π)=−Acos(ωt)=−3cos(πt). …
- AP EAPCET 2026Set eng-2026-05-13-FN1 markMCQQ.In simple harmonic motion, at mean position (A) KE maximum (B) PE maximum (C) KE zero (D) Acceleration maximum
›Reveal solutionSolution
Tests the basic energy/acceleration profile of SHM at the mean position. Answer: KE is maximum there.
Concept and Intuition
In SHM, total energy E=21kA2 is conserved and continuously exchanged between kinetic and potential forms as the particle oscillates. At the mean position (equilibrium, x=0), the restoring force and hence acceleration are zero, so the particle has been accelerating toward this point the entire half-swing — meaning its speed, and hence KE, peaks exactly here.
Step-by-Step Solution
- Displacement from mean position: x=0 at mean position.
- Potential energy: PE=21kx2=0 at x=0 — minimum (zero), not maximum.
- Acceleration: a=−ω2x=0 at x=0 — zero, not maximum (acceleration is maximum at extreme positions). …
- AP EAPCET 2026Set eng-2026-05-13-FN1 markMCQQ.A particle starting from the origin executes simple harmonic motion along x-axis. Its velocity at any instant t is given by vx=22cos(2πt) cms−1. The total distance covered by the particle in time t=4.5 sec (A) 74.5 cm (B) 51.4 cm (C) 65.9 cm (D) 49.8 cm
›Reveal solutionSolution
Tests computing total distance in SHM over a non-integer number of periods using the velocity equation. Answer: ≈65.9 cm.
Concept and Intuition
Since vx=22cos(πt/2) is maximum at t=0, the particle starts at the mean position (x=0) moving with maximum speed — this fixes x(t)=Asin(ωt) with Aω=22. Total distance traveled per full period is 4A (since the particle sweeps mean→extreme→mean→extreme→mean, covering A four times). For a leftover fractional time, we track where the particle actually is and add only the distance covered in that leftover interval, being careful whether it reverses direction within it.
Step-by-Step Solution
- Compare vx=22cos(πt/2) with vx=Aωcos(ωt): ω=π/2 rads−1 and Aω=22⇒A=π/222=π44≈14.01 cm.
- Period T=ω2π=π/22π=4 s.
- t=4.5 s =1×T+0.5 s. In one full period the particle covers 4A≈4(14.01)=56.05 cm.
- Since T=4 s, the state (position and direction) at t=4 s is identical to t=0 s (mean position, moving in +x). So the extra 0.5 s behaves exactly like the interval t=0→0.5 s.
- Displacement: x(t)=Asin(ωt) (zero at t=0, matching the cosine velocity). At t=0.5: x=Asin(π/4)=14.01×0.7071≈9.91 cm. …
- AP EAPCET 2026Set eng-2026-05-14-FN1 markMCQQ.A particle is executing simple harmonic motion with time period T and amplitude A. The distance travelled by the particle in 12T time starting from rest is (A) 2A(3−2) (B) 2A(2−3) (C) (2−3)2A (D) (3−2)2A
›Reveal solutionSolution
This tests SHM position as a function of time when starting from rest (i.e., from an extreme position). The answer is 2A(2−3).
Concept and Intuition
"Starting from rest" in SHM means the particle begins at an extreme (turning) point, where velocity is momentarily zero and displacement is maximum (x=A). The position as a function of time measured from that instant is x(t)=Acos(ωt), since cos(0)=1 gives x=A at t=0 and velocity ∝−sin(ωt)=0 at t=0. The distance travelled toward the mean position is A−x(t).
Step-by-Step Solution
- Angular frequency: ω=T2π.
- Position from extreme: x(t)=Acos(ωt).
- At t=12T: ωt=T2π×12T=6π (i.e. 30∘).
- x=Acos(30∘)=A⋅23=2A3. …
- AP EAPCET 2026Set eng-2026-05-14-AN1 markMCQQ.The displacement of particle executing simple harmonic motion is given by x=6sin(2πt+4π) m. The amplitude and maximum speed are given by (A) 4m, 2π ms−1 (B) 6m, 4π ms−1 (C) 6m, 12π ms−1 (D) 2m, 12π ms−1
›Reveal solutionSolution
Reading amplitude and angular frequency directly off the SHM equation and using vmax=Aω gives amplitude 6 m and max speed 12π ms−1.
Concept and Intuition
Any SHM displacement equation of the form x=Asin(ωt+ϕ) directly reveals the amplitude A and angular frequency ω by inspection. The maximum speed in SHM always occurs while passing through the mean position, and its magnitude is Aω (from differentiating x with respect to time and taking the maximum value of the cosine term).
Step-by-Step Solution
- Given x=6sin(2πt+4π), matching to x=Asin(ωt+ϕ): A=6 m, ω=2π rad/s.
- Velocity: v=dtdx=6(2π)cos(2πt+4π)=12πcos(⋯). …
- AP EAPCET 2026Set eng-2026-05-13-AN1 markMCQQ.Two Simple Harmonic Motions are given by y1=Asin(2πt+ϕ) and y2=Bsin(32πt+ϕ). The phase difference between these two after one sec is (A) π (B) 2π (C) 4π (D) 6π
›Reveal solutionSolution
The two SHMs share the same initial phase ϕ but different angular frequencies; subtracting their phase expressions and evaluating at t=1 s gives a phase difference of π/6 — option (D).
Concept and Intuition
Both oscillations start with the same phase constant ϕ, but because their angular frequencies differ (π/2 vs 2π/3), the two phases drift apart as time passes. The phase difference at any instant is simply the difference of the two full phase expressions (the ϕ cancels out since both share it).
Step-by-Step Solution
- Phase of y1: ϕ1(t)=2πt+ϕ.
- Phase of y2: ϕ2(t)=32πt+ϕ.
- Phase difference: Δϕ(t)=ϕ2(t)−ϕ1(t)=(32π−2π)t (the ϕ terms cancel). …
- AP EAPCET 2026Set eng-2026-05-15-AN1 markMCQQ.The energy of a particle executing Simple Harmonic Motion (SHM) is given by E=Ax2+BV2. Here 'x' is the displacement of the particle from mean position and 'V' is its velocity at 'x' and A and B are constants. The INCORRECT statement is (A) Amplitude is A2E (B) Maximum velocity is BE (C) Time period is 2πAB (D) Maximum acceleration is BEA
›Reveal solutionSolution
This tests deriving amplitude, maximum velocity, time period, and maximum acceleration from a given SHM energy expression E=Ax2+BV2, and spotting which standard-looking statement is wrong. The answer is (A) — the amplitude formula given is off by a factor of 2.
Concept and Intuition
In SHM, total mechanical energy is conserved and equals E=21mω2x2+21mV2 at any instant (PE + KE). By matching this to the given form E=Ax2+BV2, we identify A=21mω2 and B=21m, and can then derive amplitude, max velocity, time period, and max acceleration purely from A, B, and E — checking each option against the true SHM relations.
Step-by-Step Solution
- Standard SHM energy: E=21mω2x2+21mV2 (constant total energy). Matching coefficients with E=Ax2+BV2: A=21mω2, B=21m. So m=2B and ω2=m2A=2B2A=BA.
- Maximum velocity occurs at x=0 (mean position), where all energy is kinetic: E=BVmax2⇒Vmax=E/B. This matches option (B) — correct statement.
- Amplitude a occurs where V=0 (extreme position), where all energy is potential: E=Aa2⇒a=E/A. Option (A) states the amplitude is 2E/A — this has an extra factor of 2 that shouldn't be there, so option (A) is WRONG.
- Time period: T=ω2π=2πω21=2πAB (since ω2=A/B). This matches option (C) — correct statement. …
- AP EAPCET 2026Set eng-2026-05-15-FN1 markMCQQ.A particle executes two simple harmonic motions along mutually perpendicular axes, given by x=Asin(ω1t), y=Bcos(ω2t) where A=B and ω1=ω2. Which of the following best describes the resultant motion of the particle? (A) Straight line (B) Circular path (C) Elliptical path (D) Spiral path
›Reveal solutionSolution
Two perpendicular SHMs of equal frequency with a 90∘ phase difference trace an ellipse in general, collapsing to a circle only in the special case of equal amplitudes. Here A=B, so the path is elliptical.
Concept and Intuition
Combining perpendicular SHMs is a classic way to generate Lissajous figures. When the two frequencies are equal and the phase difference is exactly 90∘ (as sin and cos are), the resulting path is always a closed ellipse whose semi-axes equal the two component amplitudes. Only when those amplitudes happen to be equal does the ellipse become a perfect circle. Since we're told A=B, the shape must remain a genuine ellipse.
Step-by-Step Solution
- Given x=Asin(ω1t) and y=Bcos(ω2t) with ω1=ω2=ω.
- Rewrite: Ax=sinωt and By=cosωt.
- Square and add: (Ax)2+(By)2=sin2ωt+cos2ωt=1. …
- AP EAPCET 2026Set eng-2026-05-18-FN1 markMCQQ.A body executes SHM under the influence of one force and has the time period of T1 seconds. The same body executes SHM with a time period of T2 seconds when under the influence of another force separately. When both forces act simultaneously and in the same direction, then the time period of the same body is (A) (T1+T2) sec (B) T12+T22 sec (C) T1T2T1+T2 sec (D) T12+T22T12T22 sec
›Reveal solutionSolution
When two SHM-producing forces act together, their effective force constants (each ∝1/T2) add, giving a combined period T=T12+T22T12T22.
Concept and Intuition
A restoring force that produces SHM behaves like a spring with some effective force constant k=mω2. If two such restoring forces act on the same body simultaneously and in the same sense (both pulling toward the same equilibrium), their force constants simply add — exactly like two springs in parallel — giving a stiffer combined restoring force and hence a different (shorter) period.
Step-by-Step Solution
- For a body of mass m under one force alone with period T1: ω1=T12π, so effective force constant k1=mω12=T124π2m.
- Similarly for the second force alone: k2=T224π2m.
- When both forces act simultaneously in the same direction (both restoring toward the same point), they combine like parallel springs: keff=k1+k2=4π2m(T121+T221).
- New angular frequency: ωeff2=mkeff=4π2(T121+T221). …
- AP EAPCET 2026Set ap-2026-05-19-FN1 markMCQQ.For a body in simple harmonic motion, Potential energy (PE), Kinetic energy (KE), Total energy (TE) are measured as a function of displacement x. Which of the following statements is true? (A) KE is maximum when x=0 (B) TE is zero when x=0 (C) KE is maximum when x is maximum (D) PE is maximum when x=0
›Reveal solutionSolution
Tests how KE, PE and TE vary with displacement in SHM — KE peaks at the mean position, PE peaks at the extremes, and TE is constant.
Concept and Intuition
A particle in SHM trades energy continuously between kinetic and potential forms while the total mechanical energy stays fixed (no non-conservative forces). Speed is greatest as the particle passes through the mean position (it has "picked up" all the energy that was stored as potential energy at the extremes) and speed is zero exactly at the extremes, where all the energy is potential.
Step-by-Step Solution
- For SHM, x=asin(ωt), so v=aωcos(ωt), giving v2=ω2(a2−x2).
- KE=21mv2=21mω2(a2−x2). This is maximum when x=0 (since a2−x2 is largest there) and zero when x=±a.
- PE=21mω2x2 is the complement: zero at x=0, maximum at x=±a.
- TE=KE+PE=21mω2a2, independent of x — never zero (for a=0) and never varies with position. …
- AP EAPCET 2026Set ap-2026-05-19-FN1 markMCQQ.A particle executes simple harmonic motion with time period 'T' and amplitude 'a'. The magnitude of average velocity of the particle over the time interval during which it travels a distance 2a from extreme position is (A) Ta (B) T2a (C) 2Ta (D) T3a
›Reveal solutionSolution
Tests average velocity (distance/time, not instantaneous velocity) for a specific segment of SHM measured from the extreme position.
Concept and Intuition
Average velocity over an interval is just total distance covered divided by the time taken — it doesn't need calculus once we know the time. Measuring the phase from the extreme position (where velocity is zero) makes the position-time relation a cosine, which is the convenient choice here.
Step-by-Step Solution
- Take the extreme position as the reference: x(t)=acos(ωt), with ω=T2π.
- The particle has travelled a distance a/2 from the extreme, so its new position (measured from the centre) is x=a−2a=2a.
- Set acos(ωt)=2a⇒cos(ωt)=21⇒ωt=3π.
- So t=2π/Tπ/3=6T. …
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