Draw a graph between displacement from mean position and time for a body executing free vibration in a vacuum.

When a body is vibrating freely in a vacuum then the amplitude and frequency should remain constant but if a body vibrates in a medium then the particles present in the medium offer friction which allows the vibrating body to lose energy due to which the amplitude of the wave decreases. The constant amplitude and frequency can be maintained by the body only if it is vibrating in a vacuum. This is also known as simple harmonic vibration. Therefore, the required graph for the object vibrating in a vacuum can be given as-

Why does the amplitude of a vibrating body continuously decrease during damped vibrations?

Because of the frictional (resistive) force exerted by the surrounding medium, the amplitude of a vibrating body continuously decreases during damped vibrations. In these waves, the energy is dissipated and the vibrating body comes to rest in its equilibrium position after some time. A tuning fork that is vibrating in air shows damped vibration.

What do you understand by free vibrations of a body?

Free (or natural) vibrations are the periodic vibrations of a body in the absence of any external force. Free vibration are oscillation where the total energy stays the same this means that the amplitude of the vibration stays the same. Example: vibration or oscillation of a pendulum, etc.

Two pendulums C and D are suspended from a wire as shown in the given figure. Pendulum C is made to oscillate by displacing it from its mean position. It is seen that D also starts oscillating. What is the name of the phenomenon when the length of D is made equal to C ?

If the length of D is made equal to C , in this case, both will have the same frequency and the amplitude. The time period for both will also be the same. In this case both the pendulum D and C will oscillate with same frequency. Hence, in this case the frequency of external periodic force will be equal to natural frequency of vibration which gives raise to the phenomena of resonance. When the natural frequency of oscillation becomes equal to the forced frequency of oscillation, the amplitude of oscillation becomes maximum. This is called resonance.

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 7 - Sound>ICSE-2020>Q 17

MEDIUM

10th ICSE

IMPORTANT

Earn 100

A sound wave travelling in water has wavelength $0.4 m$ . Is this wave audible in air? (The speed of sound in water $= 1400 m s^{- 1}$ )

Important Questions on Sound

MEDIUM

10th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 7 - Sound>ICSE-2020>Q 18

Name the system which enables us to locate underwater objects by transmitting ultrasonic waves and detecting the reflecting impulse.

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IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 7 - Sound>ICSE-2020>Q 19

What are acoustically measurable quantities related to pitch and loudness?

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10th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 7 - Sound>ICSE-2020>Q 20

When a tuning fork [vibrating] is held close to the ear, one hears a faint hum. The same [vibrating tuning fork] is held such that its stem is in contact with the table surface, then one hears a loud sound. Explain.

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IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 7 - Sound>ICSE-2020>Q 21

A man standing in front of a vertical cliff fires a gun. He hears the echo after