Guess Paper Year 2011
CBSE Class IX
Subject: Physics
(Set-1)

1. Wave motion transfer
(a) momentum
(b) velocity
(c) energy
(d) mass

2. Speed of light wave is higher than the speed of sound in air by
(a) 1000000 times
(b) 100000000 times
(c) 10000000 times
(d) 300000 times

3. Sonic booms are caused by the combination of
(a) super sonic speed and pressure variation
(b) infrasonic speed and pressure variation
(c) ultrasonic sound and pressure variation
(d) pressure variation only

4. The term ultrasonic, supersonic &infrasonic mean
(a) decreasing frequency
(b) increasing frequency
(c) increasing loudness
(d) can not be related

5. Two audio devices of same brand differ in
(a) quality of sound
(b) reverberation
(c) frequency of sound created
(d) loudness

6. A pulse is
(a) a short term disturbance
(b) doesn’t repeat
(c) can travel
(d) all of these

7. Noise and music differ by
(a) quality
(b) ton
(c) note
(d) pitch

8. In longitudinal waves , the vibration of molecules will be
(a) perpendicular to the propagation
(b) parallel to the propagation
(c) depend upon the humidity
(c) none of these

10. Sound is produced when
(a) The prongs of the fork are vibrated
(b) Stretched rubber band is plucked
(c) Mechanical vibrations are produced
(d) All of these

Answer these questions below:

1. What is the difference between supersonic and ultrasonic?

2. Give two medicinal uses of ultrasound.

1. What is sonic boom?

2. Name two different forms of wave motion and express how they are created.

3. Name two physical quantities involved in the motion of sound in a medium.

4. Give two examples for the fact that mechanical vibrations produce sound energy.

5. In a thunderstorm, does the light flash reach first or the sound? Why?

6. What is an echo? What are conditions to get an echo?

7. Name three devices whose working is based of the principle of reflection.

8. What do you mean by note and tone? Give differences between music and noise?

Numerical:

1. A wave pulse on a string moves a distance of 8 m in 0.05 s.
(i) Find the velocity of the pulse.
(ii) What would be the wavelength of the wave on the string if its frequency is 200 Hz?

2. A sonar device on a submarine sends out a signal and receives an echo 5 s later. Calculate the speed of sound in water, if the distance of the object from the submarine is 3625 m.

3. A child hears an echo from a cliff 4 seconds after the sound from a powerful cracker is produced. How far away is the cliff from the child? (Take velocity of the sound in air as 330m/s).

4. Ocean waves of time period of 0.01s have a speed of 15 m/s. What is the wavelength of these waves? What is the distance between a crest and the adjoining through?

5. What is the minimum size of a room to get an echo if the velocity of sound is 320 m/s?