Chapter 10: Simple Harmonic Motion

           Chp10 : Simple Harmonic Motion

                                     Exercise Questions

Answer the following questions.

1.What is Simple Harmonic Motion? What are the necessary conditions for a body to execute simple harmonic motion? 

Ans.  Simple Harmonic Motion is the to and fro oscillatory motion in which acceleration of the body is directly proportional to displacement of body from mean position and is always directed towards the Mean position. 

Necessary Conditions:

• A body executing Simple Harmonic Motion  always vibrates at a fixed position.
• Its acceleration is always directed towards mean position
• The magnitude of acceleration is always directly propotional to its displacement from the mean position i.e acceleration will be zero at mean position while it will be maximum at extreme position
• Its velocity is maximum at the mean position and zero at the extreme position
• Kinetic Energy is maximum at mean position an zero at extreme position while Potential Energy is maximum at extreme position and zero at mean position.

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

Ans. Common Examples of Simple Harmonic Motion are:

1. Motion of Simple Pendulum
2. Up and Down Motion of cork in water
3. Motion of body in swing

3.What are damped oscillations. How damping progressively reduces amplitude of oscillations?

Ans.  Any oscillation in which the amplitude of the oscillating quantity decreases with time is called damped oscillation.

Damping Reduces Amplitude :

Practically in all system the force of friction and resistance retards the motion, so the system do not oscillate for long time period. Friction reduces mechanical energy of a system as time passes. Due to this reason Damping progressively reduces amplitude of oscillations.

4. How can you define the term wave? Elaborate the difference between mechanical and electromagnetic wave.Give example of each.

Ans. Wave :

        A wave is the disturbance in the medium causing the particles of the medium to undergo vibratory motion and it carries energy from one place to another.

Mechanical Waves :

Def. Waves that require a medium for its propagation are called mechanical waves .

Example: Sound waves

Electromagnetic Waves:

Def. Waves that do not require a medium for its propagation are called electromagnetic waves.

Example: Light waves

5. Distinguish between longitudinal and transverse waves with suitable example.

 In Longitudinal Waves,  The vibratory motion of particles is parallel to direction of propagation  of waves .It consists of Compression and Rarefractions.   E.g  Sound Wave, While     In Transverse Waves,  The vibratory motion of particles is perpendicular to direction of propagation  of waves.It consists of crests and trought.    E.g Light wave 

                                                   

6. Derive a relationship between velocity, frequency and wavelength of a wave.

Ans.    Velocity = distance/time

            v =    d/t

             v=      λ /T

                ∵f= 1/T

hence,    v = f λ   

    

7. Define Spring Constant. Write its formula also?      

Ans. K is a constant called the spring constant. The value of K is a measure of the stiffness of the spring.            Formula:        K = -  F/X

8.      Explain the following properties of waves with reference to ripple tank experiment.  

Ans.           Reflection: When waves moving in one medium fail on the surface of another medium they bounce back into the first medium such that the angle of incidence is equal to the angle of reflection.  

                   Refraction: When a wave from one medium enters in the second medium at some angle, its direction of travel changes is called Refraction.   

                   Diffraction: The bending or spreading of waves around the sharp edges or corner of obstacles or slits is called Diffraction.

    

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

Ans. No, increasing the frequency will not increase the wavelength as both the quantities are inversely proportional to each other. Hence increasing the frequency will cause a decrease in the wavelength.

10. Draw a wave with an amplitude of 2cm and a wavelength of 4cm. Label crest and trough on wave.                                                                                                                                                                   Ans.