Physics 10th Chapter 10 Simple Harmonic Motion Exercise Question and Conceptual Question

Physics 10th Chapter 10 Simple Harmonic Motion Conceptual Questions

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10.1 If the length of a simple pendulum is doubled, what will be the change in its time period?

Ans: If the length of simple pendulum is doubled its time period will be √2 T.

As we know that 

Time period of simple pendulum

T=2π√(l/g) 

When l = 2l

Then

T'=2π√(2l/g) 

T'=v2(2π√(l/g)) 

T'=√2 T

10.2 A ball is dropped from a certain height onto the floor and keeps bouncing. Is the motion of the ball simple harmonic? Explain.

Ans: No, the motion of the ball is not executing SHM. Because during the bouncing of ball mean position of not specified and it does not fulfill the conditions of simple harmonic motion.

10.3 A student performed two experiments with a simple pendulum. He/ She used two bobs of different masses by keeping other parameters constant. To his/ her astonishment the time period of the pendulum did not change! Why?

Ans: Time period of the simple pendulum is independent of mass. Time period of the simple pendulum does not change, with the change of mass, because it does not depend upon the mass of the body as: T=2π√(l/g) 

10.4 What types of waves do not require any material medium for their propagation?

Ans: Electromagnetic waves do not require material medium to propagate.

10.5 Plane waves in the ripple tank undergo refraction, when they move from deep to shallow water. What change does occur in the speed of the waves?

Ans: The water waves enter into the region of shallow water, their wavelength decreases as given by the formula: 

v = fλ

As wavelength decreases, the speed of the wave also decreases.

Physics 10th Chapter 10 Simple Harmonic Motion Exercise Questions

10.1 What is simple harmonic motion? What are the necessary conditions for a body to execute simple harmonic motion?

Ans: Simple Harmonic motion (SHM) is a to and fro oscillatory motion in which acceleration of the body is directly proportional to the displacement of the body from the mean position and is always directed towards the mean position.

Necessary conditions for SHM

• A body executing SHM always vibrates about a fixed position.
• Its acceleration is always directed towards the mean position.
• The magnitude of acceleration is always directly proportional to its displacement from the mean position i.e., acceleration will be zero at the mean position while it will be maximum ate h extreme position.
• Its velocity is maximum at the mean position and zero at the extreme position.

10.2 Think of several examples of motion in everyday life that are simple harmonic.

Ans:  Motion of mass attached to a spring, Ball and Bowl system, Motion of simple pendulum, swing, and pendulum clock.

10.3 What are damped oscillations? How damping progressively reduces the amplitude of oscillation?

Ans: The oscillation of a system in the presence of some resistive force is damped oscillations.

Vibratory motion of ideal systems in the absence of any friction or resistance continues indefinitely under the action of a restoring force. Practically, in all systems, the force of friction retards the motion, so the systems do not oscillate indefinitely. The friction reduces the mechanical energy of the system as time passes, and the motion is said to be damped, this damping progressively reduces the amplitude of the vibration of motion.

10.4 How can you define the term wave? Elaborate he difference between mechanical and electromagnetic waves. Give examples of each.

Ans: Wave: A wave is a disturbance in the medium which causes the particles of the medium to undergo vibratory motion about their mean position in equal intervals of time.

Mechanical Waves: Waves which require any medium for their propagation are called mechanical waves. E.g. water waves, sound waves.

Electromagnetic Waves: Waves which do not require any medium for their propagation are called electromagnetic waves. E.g. Radio-waves, X-rays, heat.

10.5 Distinguish between longitudinal and transverse waves with suitable examples.

Ans: Longitudinal wave: In longitudinal waves the particles of the medium move back and forth along the direction of propagation of wave. E.g. Sound waves.

Transverse wave: In transverse wave the vibratory motion of particles of the medium is perpendicular to the direction of propagation of waves. E.g. Water waves.

10.6 Draw a transverse wave with amplitude of 2cm and a wavelength of 4cm. Label a crest and trough on the wave.

Ans: 

10.7 Derive a relationship between velocity, frequency and wavelength of a wave. Write a formula relating velocity of a wave to its time period and wavelength.

Ans: The relationship between velocity, frequency and wavelength of a wave is called wave equation. Wave is a disturbance in a medium which travels from one place toe another and hence has a specific velocity of travelling. This is called the velocity of wave which is defined by:

Velocity = distance/time

v = d/t

If time taken by the wave in moving from one point to another is equal to its time period T, then the distance covered by the wave will be equal to one wavelength ?, hence we can write:

v = λ/T (Formula showing relation of velocity of wave to its time period and wavelength)

But time period T, is reciprocal of the frequency f, i.e., T = 1/f

Therefore, v = fλ Which is true for longitudinal and transverse waves.

10.8 Waves are the means of energy transfer without transfer of matter. Justify this statement with the help of a simple experiment.

Ans: Energy can be transferred from one place to another through waves but it does not transfer matter.

For Examples. Drop a stone into a pond of water. Water waves will be produced on the surface of water and will travel outwards. Place a cork at some distance from the falling stone. When waves reach the cork, it will move up and down along-with the motion of the water particles by getting energy form the waves. This activity shows that water waves transfer energy from one place toe another without transferring matter, i.e., water.

10.9 Explain the following properties of waves with reference to ripple tank experiment:

a. Reflection b. Refraction c. Diffraction

Ans: Reflection: When a wave travelling from one medium falls on the surface of another medium, it may bounce back into the first medium. This phenomenon is called reflection of waves.

Refraction: When waves from one medium enter the second medium at some angle, their direction of travel may change. This phenomenon is called refraction of waves.

Diffraction: The bending of waves around obstacles or sharp edges is called diffraction of waves.

10.10 Does increasing the frequency of a wave also increase its wavelength? If not, how are these quantities related?

Ans: Increasing the frequency does not increase the wavelength of the wave. Frequency of the wave and wavelength are related according to the relation v = f?

Extra Questions

10.11 Define Crest and Trough.

Ans: Crest: In transverse wave the points at which the particles of the medium are above the mean position.

Trough: In transverse wave the points at which the particles of the medium are below the mean position.

10.12 Define Compression and Rarefaction.

Ans: Compression: In longitudinal wave the regions where the particles of the medium are closed together.

Rarefaction: In longitudinal wave the regions where the particles of the medium are spaced apart.

10.13 Define amplitude.

Ans: The maximum displacement of a vibrating body on either side from its mean position is called its amplitude.

10.14 Define vibration.

Ans: One complete round trip of a vibrating body about its mean position is called one vibration.

10.15 Define time period.

Ans: The time taken by a vibrating body to complete one vibration is called time period. T = 1/f.

10.16 Define frequency.

Ans: The number of vibration or cycles of a vibrating body in one second is called its frequency. It is reciprocal of time period i.e., f = 1/T. Its unit is cycle per sec, Hertz (Hz) or vib/sec.