Simple Harmonic Motion Questions and Answers Class 11 Physics

Q: Why does a pendulum clock lose time at higher altitudes?

At higher altitudes, gravitational acceleration (g) decreases because the distance from Earth's centre increases. Since the time period of a pendulum is T = 2π√(l/g), a smaller value of g makes T larger. Each oscillation takes fractionally longer, causing the clock to complete fewer oscillations per hour and therefore show a time that progressively falls behind — it loses time.

Q: What is the difference between periodic motion and SHM?

All SHM is periodic, but not all periodic motion is SHM. Periodic motion simply repeats after a fixed time interval. SHM is a special case where the restoring force obeys F = –kx. A rotating wheel is periodic but not SHM. A swinging pendulum (small angles) is both periodic and approximately SHM. The key distinguishing test is whether the force-displacement relationship is linear.

Q: What is Simple Harmonic Motion in simple terms?

Simple Harmonic Motion is a type of periodic motion where a particle oscillates about a fixed mean position, with its acceleration always directed toward the mean position and proportional to its displacement from it. Mathematically, this means a = –ω²x. The motion is sinusoidal in nature — displacement, velocity, and acceleration all vary as sine or cosine functions of time

Q: What is resonance and why is it dangerous in structures?

Resonance occurs when an external periodic force is applied to a system at exactly its natural frequency. At resonance, energy transfer to the system is maximally efficient, causing the amplitude of oscillation to grow very large — theoretically without limit in the absence of damping. In structures like bridges or buildings, resonance can produce vibrations large enough to cause mechanical failure, which is why soldiers break step on suspension bridges and engineers design buildings with resonance-avoiding natural frequencies.

Q: What happens to the time period of a spring if it is cut in half?

When a spring of spring constant k is cut in half, each half has a spring constant of 2k (shorter springs are stiffer). The time period of a mass m on the half-spring becomes T' = 2π√(m/2k) = T/√2, where T is the original period. So cutting the spring in half decreases the time period by a factor of √2 (makes it faster)

Q: Does the mass of a pendulum bob affect its time period?

No. The time period T = 2π√(l/g) has no mass term. This is because both the restoring force (gravity component) and the inertia of the bob are proportional to mass — they cancel out exactly. This is the same reason all objects fall at the same rate in a gravitational field, regardless of mass (Galileo's equivalence principle).

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eSaral Academic and Editorial Team

10th June 2026

4 min read

Summary

Simple Harmonic Motion (SHM) questions for Class 11 Physics cover time period derivations, energy in SHM, simple pendulum behaviour, spring-mass systems, and periodic vs non-periodic motion. Key topics tested in CBSE boards and JEE Main include the effect of gravity on pendulums, resonance, and U-tube oscillations. The standard formula for time period is T = 2π√(l/g) for a pendulum and T = 2π√(m/k) for a spring-mass system.

Simple Harmonic Motion Questions and Answers Class 11 Physics

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Get (SHM) simple harmonic motion questions and answers for physics class 11 exams. View 11th Physics important questions for exam point of view. These important questions will play a significant role in clearing the concepts of Physics chapters. This question bank is designed by expert faculties keeping the NCERT in mind and the questions are updated with respect to upcoming Board exams. You will get all the important questions for the Class 11 Physics chapter-wise CBSE. Click Here for Detailed Notes of SHM along with other chapters of Physics and other subjects. [esquestion] A man with a wrist watch on his hands fall from the top of a tower. Does the watch give the correct time? #sol# [/esquestion] [esquestion] A vibrating simple pendulum of period is placed in a lift which is accelerating downwards. What will be the effect on the time period? #sol# [/esquestion] [esquestion] Where is tension maximum in the string of a simple pendulum? #sol# [/esquestion] [esquestion] Can a motion be oscillatory but not simple harmonic? If your answer is yes give an example and if not explain why? #sol# [/esquestion] [esquestion] Which of the following examples represents nearly) S.H.M. and which represents periodic but not S.H.M.? (i) The rotation of earth about its own axis. (ii) Motion of an oscillating mercury column in a U-tube. (iii) Motion of a ball bearing inside a smooth curved bowl when released from a point slightly above the lower most position. (iv) General vibration of polyatomic molecule about its equilibrium configuration. #sol# [/esquestion] [esquestion] A girl is sitting on a swing. Another girl sits by her side. What will be the effect on the periodic time of the swing? #sol# No effect, as periodic time is independent of mass. [/esquestion] [esquestion] Given below are $(x-t)$ plots for linear motion of a particle. Which of the plots represent periodic motion ? What is the period of motion (in case of periodic motion)? #sol# [/esquestion] [esquestion] The bob of a vibrating simple pendulum is made of ice. How will the period of swing will charge when ice starts melting? #sol# The period of swing of simple pendulum will remain unchanged till the location of centre of gravity of the bob left after melting the ice remains at a fixed distance from the point of suspension. But, if the centre of gravity of ice bob after melting is raised upwards, then the effective length of pendulum decreases and hence the time period of swing decreases. If the centre of gravity of ice shifts on lower side, the time period of swing increases. [/esquestion] [esquestion] A ball of mass 'm' is dropped in a tunnel along the diameter of earth from a height 'h' (h< <R) above the surface of earth. Is the motion simple harmonic? #sol# [/esquestion] [esquestion] Which of the following functions of time represent (a) Periodic (b) Non-periodic motion ? Give the period of for each periodic motion $(\omega$ is any positive constant). (ii) sin $\omega t+\cos \omega t$ (ii) $\sin \omega t+\cos 2 \omega t+\sin 4 \omega t$ (iii) Se $^{\circ t}$ (iv) $\log \omega t$ #sol# [/esquestion] [esquestion] If a pendulum clock is taken on the mountain top, does it lose or gain time, assuming it is correct at a lower elevation? #sol# [/esquestion] [esquestion] The soldiers marching on a suspended bridge are advised to go out of steps. Why? #sol# [/esquestion] [esquestion] Glass window-panes may be broken by a far away explosion. Explain why? #sol# [/esquestion] [esquestion] Find expression for time period and frequency for the oscillations of a liquid in a U-tube. #sol# [/esquestion] [esquestion] Explain the oscillations of a loaded spring and find the expression for time period and frequency in case of vertical spring. #sol# [/esquestion] Learn the concepts related to simple harmonic motion with these important questions and answers. eSaral provides you complete edge to prepare for Board and Competitive Exams like JEE, NEET, BITSAT, etc. We have transformed classroom in such a way that a student can study anytime anywhere. With the help of AI we have made the learning Personalized, adaptive and accessible for each and every one. Visit eSaral Website to download or view free study material for JEE & NEET. Also get to know about the strategies to Crack Exam in limited time period.

Frequently Asked Questions

Why does a pendulum clock lose time at higher altitudes?

At higher altitudes, gravitational acceleration (g) decreases because the distance from Earth's centre increases. Since the time period of a pendulum is T = 2π√(l/g), a smaller value of g makes T larger. Each oscillation takes fractionally longer, causing the clock to complete fewer oscillations per hour and therefore show a time that progressively falls behind — it loses time.

What is the difference between periodic motion and SHM?

All SHM is periodic, but not all periodic motion is SHM. Periodic motion simply repeats after a fixed time interval. SHM is a special case where the restoring force obeys F = –kx. A rotating wheel is periodic but not SHM. A swinging pendulum (small angles) is both periodic and approximately SHM. The key distinguishing test is whether the force-displacement relationship is linear.

What is Simple Harmonic Motion in simple terms?

Simple Harmonic Motion is a type of periodic motion where a particle oscillates about a fixed mean position, with its acceleration always directed toward the mean position and proportional to its displacement from it. Mathematically, this means a = –ω²x. The motion is sinusoidal in nature — displacement, velocity, and acceleration all vary as sine or cosine functions of time

What is resonance and why is it dangerous in structures?

Resonance occurs when an external periodic force is applied to a system at exactly its natural frequency. At resonance, energy transfer to the system is maximally efficient, causing the amplitude of oscillation to grow very large — theoretically without limit in the absence of damping. In structures like bridges or buildings, resonance can produce vibrations large enough to cause mechanical failure, which is why soldiers break step on suspension bridges and engineers design buildings with resonance-avoiding natural frequencies.

What happens to the time period of a spring if it is cut in half?

When a spring of spring constant k is cut in half, each half has a spring constant of 2k (shorter springs are stiffer). The time period of a mass m on the half-spring becomes T' = 2π√(m/2k) = T/√2, where T is the original period. So cutting the spring in half decreases the time period by a factor of √2 (makes it faster)

Does the mass of a pendulum bob affect its time period?

No. The time period T = 2π√(l/g) has no mass term. This is because both the restoring force (gravity component) and the inertia of the bob are proportional to mass — they cancel out exactly. This is the same reason all objects fall at the same rate in a gravitational field, regardless of mass (Galileo's equivalence principle).

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Simple Harmonic Motion Questions and Answers Class 11 Physics

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