Class 10 Physics Unit 10 – Simple Harmonic Motion & Waves Notes – MCQs, Short & Long Questions

Class 10 Physics Unit 10 covers important concepts including Simple Harmonic Motion (SHM), Damped Oscillations, Wave Motion, Types of Mechanical Waves, and Ripple Tank experiments. In this chapter, students learn how objects perform periodic motion under a restoring force and how energy is transferred through waves without the transfer of matter. Key terms such as amplitude, time period, frequency, wavelength, and wave speed are explained in a clear and easy manner.

These notes are prepared according to the latest board exam pattern and include important definitions, formulas, MCQs, short questions, and long questions for complete exam preparation. With proper understanding of SHM and wave motion, students can improve their conceptual clarity and confidently attempt numerical and theoretical questions in the board examination.

Important MCQs – Unit 10 Simple Harmonic Motion & Waves

1. Which of the following is an example of simple harmonic motion (SHM)?
(a) The motion of a simple pendulum ✅
(b) The motion of a ceiling fan
(c) The spinning of the Earth on its axis
(d) A bouncing ball on a floor

2. Which of the following is a method of energy transfer?
(a) Conduction
(b) Radiation
(c) Wave motion
(d) All of these ✅

Q: What is the correct formula to find the speed of a wave?
(a) v=f+λ
(b) v=f/λ
(c) v=f×λ ✅
(d) v=λ/f

4. Which of the following is an example of SHM?
(a) A freely falling ball
(b) A rotating fan
(c) A mass attached to a spring ✅
(d) A moving car

5. Which of the following is an example of simple harmonic motion (SHM)?
(a) Car moving on a straight road
(b) A fan rotating
(c) Mass-spring system on a frictionless surface ✅
(d) Object falling freely

6. Hooke’s Law is mathematically written as:
(a) F=kx
(b) F=ma
(c) F=−kx ✅
(d) F=mgh

Short Questions – Unit 10 Simple Harmonic Motion & Waves

1. What is Simple Harmonic Motion (SHM)?

Answer:
Simple Harmonic Motion (SHM) is a to-and-fro oscillatory motion in which the acceleration is directly proportional to the displacement from the mean position and is directed towards it.

Explanation:

• In SHM, an object repeatedly moves about an equilibrium position.

• The restoring force always acts towards the mean position and is proportional to the displacement.

• Examples include a simple pendulum and a mass-spring system.

2. Differentiate between mechanical and electromagnetic waves.

Answer:

• Mechanical waves: Need a medium (solid, liquid, or gas) for propagation.

• Electromagnetic waves: Do not require any medium and can travel through a vacuum.

Explanation:

• Mechanical waves transfer energy through the vibration of particles in a medium (e.g., sound waves, water waves).

• Electromagnetic waves transfer energy through oscillating electric and magnetic fields and can propagate in empty space (e.g., light, radio waves).

3. Define vibration, amplitude, time period, and frequency.

Answer:

• Vibration: One complete to-and-fro motion of a body.

• Amplitude: Maximum displacement of the body from its mean position.

• Time Period (T): Time taken for one complete vibration.

• Frequency (f): Number of vibrations per second. Mathematically, f=1Tf = \frac{1}{T}f=T1​.

Explanation:

• Vibration is the basic motion in Simple Harmonic Motion (SHM).

• Amplitude shows the extent of motion, while time period and frequency measure how fast the motion occurs.

• These quantities are interrelated, forming the foundation for understanding waves and oscillations.

Long Questions – Unit 10 Simple Harmonic Motion & Waves

Q1: Define Simple Harmonic Motion (SHM) and Explain with Examples

Examples:

1. Mass attached to a spring

2. Ball and bowl system

3. Simple pendulum

Definition of Simple Harmonic Motion (SHM):

Simple Harmonic Motion (SHM) is a type of oscillatory motion in which the restoring force acting on the object is:

1. Directly proportional to the displacement from the mean (equilibrium) position

2. Directed toward the mean position

In simple words:

When an object moves to and fro about a fixed point, and its acceleration is proportional to the displacement but in the opposite direction, the motion is called Simple Harmonic Motion.

Key Features of SHM:

• Motion is periodic: repeats after a fixed time

• There is a restoring force always pulling the object toward the mean position

• Acceleration is opposite in direction to displacement

(i) Mass attached to a spring (Horizontal Spring-Mass System)

Setup:

• A mass is attached to a spring placed on a frictionless horizontal surface.

• When the spring is stretched or compressed by a small distance $x$, it exerts a restoring force $F$ given by Hooke’s Law:

F=−kx

where $k$ is the spring constant.

Motion:

• When the mass is displaced from equilibrium and released:

  • The restoring force pulls it back toward the mean position.

  • The mass accelerates toward the center, passes the equilibrium due to inertia, and compresses the spring on the opposite side.

• This back-and-forth oscillatory motion continues, forming SHM.

Example: Mass-spring oscillator used in physics experiments or vibration studies.

(ii) Ball and Bowl System

Setup:

• A ball is placed at the bottom of a smooth, concave bowl (mean position $O$).

• When displaced to one side and released, gravity acts as a restoring force, pulling it toward the center.

Motion:

• The ball gains speed moving toward the center.

• Due to inertia, it moves past the mean position to the other side.

• It comes to rest, then reverses direction, repeating the motion.

Observation:

• This to-and-fro motion is periodic and shows SHM because the restoring force is proportional to the displacement from the mean position.

(iii) Simple Pendulum

Setup:

• A small bob of mass $m$ is suspended by a light, inextensible string of length L.

• The equilibrium position is when the bob hangs vertically at rest.

Working:

• When the bob is pulled sideways and released, a component of the weight of the bob acts as a restoring force, pulling it toward the mean position.

• The bob swings back and forth, crossing the equilibrium position due to inertia.

Observation:

• The motion is periodic, with the restoring force always directed toward the mean position.

• For small angles, the motion of the pendulum closely approximates SHM.

Summary:

All three systems—spring-mass, ball-in-bowl, and simple pendulum—demonstrate Simple Harmonic Motion because they share these features:

• Presence of a restoring force

• Oscillatory (to-and-fro) motion about an equilibrium point

• Restoring force proportional to displacement

Key Takeaways:

• SHM is foundational in waves, vibrations, and oscillatory systems.

• Understanding SHM helps in solving problems in physics exams, designing instruments, and explaining natural phenomena like pendulum clocks and vibrations in bridges.

 Download PDF

Download the complete chapter notes in PDF format for detailed study and exam preparation.

English Medium
 View English Medium

Urdu Medium
 View Urdu Medium PDF