Wave Motion and Sound

• Very Important Multiple Choice Questions (MCQs) with Answers of Chapter No. 8:  Wave Motion and Sound in Physics Class 11 Sindh Book Boards.
• Definition of Simple Harmonic Motion with examples
• Conditions of a Body to Execute Simple Harmonic Motion
• Motion Under Elastic Resoring Force
• Connection Between S.H.M. and Uniform Circular Motion
• Definition of Time Period with formula
• Energy of a Body Execution Simple Harmonic Motion
• Define and Explain Simple Pendulum
• Definition of Wave Motion and its types
• Definition of Mechanical Waves with examples
• Definition of Transverse Waves with examples
• Definition of Longitudinal Waves with examples
• Definition of Travelling Waves
• Stationary Or Standing Waves
• Standing Or Stationary Waves in a String
• Fundamental Frequency and Harmonics
• Describe Superposition Principle with explanation
• State and Explain Energy in Waves
• State and Explain Sonometer
• Definition of Sound and Production of Sound: (i) Infra Sonic Sound (ii) Audible Frequency Range (iii) Ultra Sonic Sound.
• Speed of Sound Waves
  
• Newton’s Formula for the Speed of Sound Wave
• Define and Explain Beats
• Production of Beats
• Analytical Treatment of Beats
• Characteristics of Musical Sound
• State and Explain Intensity and Loudness
• State and Explain Intensity Level
• Definition of Pitch of Sound
• Define and Explain Doppler’s Effect (i) When listener moves towards the stationary source of sound (ii) When listener moves away from the stationary source of sound.
  (iii) When source of sound moves towards the stationary listener.(iv) When source of sound moves away from the stationary listener. (v) When both source of sound and listener move towards each other. (vi) When both source of sound and listener move away from each other.
• State and Explain Acoustics and Reverberation
• An object is connected to one end of a horizontal spring whose other end is fixed. The object is pulled to the right (in the positive x-direction) by an externally applied force of magnitude 20 N causing the spring to stretch through a displacement of 1 cm (a) Determine the value of force constant if, the mass of the object is 4 kg (b) Determine the period of oscillation when the applied force is suddenly removed. 
• A body hanging from a spring is set into motion and the period of oscillation is found to be 0.50 s. After the body has come to rest, it is removed. How much shorter will the spring be when it comes to rest?
• A pipe has a length of 2.46 m. (a) Determine the frequencies of the fundamental mode and the first two overtones if the pipe is open at both ends. Take υ = 344 m/s as the speed of sound in air. (b) What are the frequencies determined in (a) if the pipe is closed at one end? (c) For the case of open pipe, how many harmonics are present in the normal human being hearing range (20 to 20000 Hz)?
• A standing wave is established in a 120 cm long string fixed at both ends. The string vibrates in four segments when driven at 120 Hz (a) Determine the wavelength (b) What is the fundamental frequency?
• Calculate the speed of sound in air at atmospheric pressure p = 1.01x105 N/m2 , taking γ = 1.40 and ρ = 1.2kg/m3. 
• A sound wave propagating in air has a frequency of 4000 Hz. Calculate the percent change in wave length when the wave front, initially in a region where T = 27o C, enters a region where the air temperature decreases to 10o C.
• The frequency of the second harmonic of an open pipe (open at both ends) is equal to the frequency of the second harmonic of a closed pipe (open at one end). (a) Find the ratio of the length of the closed pipe to the length of the open pipe.(b) If the fundamental frequency of the open pipe is 256 Hz, what is the length of pipe? (Use υ = 340 m/s).
• A 256 Hz tuning fork produces four beats per second when sounded with another fork of unknown frequency. What are two possible values for the unknown frequency? 
• An ambulance travels down a highway at a speed of 75 mi/h. Its siren emits sound at a frequency of 400 Hz . What frequency will heard by a person in a car traveling at 55 mi/h in the opposite direction as the car approaches the ambulance and as the car moves away from the ambulance.
• A car has siren sounding a 2 kHz tone. What frequency will be detected as stationary observer as the car approaches him at 80 km/h? Speed of sound = 1200 km/h. 
• Two cars approaching each other from opposite directions with same speed. The horn of one is blowing with the frequency of 3000 Hz and is heard by the people in the other car with the frequency of 3400 Hz. Find the speed of both cars, if speed of sound in air is 340 m/s . 
• A mass at the end of spring oscillates with a period of 0.4 sec. Find the acceleration when the displacement is 6 cm.
• A string 2m long and mass 0.004 kg, is stretched horizontally by passing one end over a pulley and attaching a 1 kg mass to it. Find the speed of the transverse waves on the string and frequency of the second harmonic.
• A 15 kg block is suspended by a spring of spring constant 5 x 103 N/m. Calculate the frequency of vibration of the block displaced from its equilibrium position when it is released. 
• A standing wave is established in a 135 cm long string fixed at both ends. The string vibrates in four loops when driven at 130 Hz. Determine the fundamental frequency.
• A 100 cm long string vibrates into four loops at 50 Hz. The linear density of the string is 4 x 10-4 gm/cm. Calculate the tension in the string. 
• A string 2 m long of mass 0.004 kg, is stretched horizontally by passing one end over a frictionless pulley and a mass of 1 kg is suspended, Find the speed of transverse waves on the string. 
• A car emitted a note of frequency 490 Hz, if the car approaching towards a stationary listener at speed of 55 km/h, what frequency will be detected by the listener. Take speed of sound as 334 m/s.
• A sound wave of frequency 500 Hz in air enters from a region of temperature 25 degrees C to a region of temperature 5 degrees C. Calculate the percent fractional change in wavelength. 
• Find the velocity of sound in a gas when two waves, of wavelengths 0.8m and 0.81, respectively, produce 4 beats per seconds.
• A string, lm long and of mass 0.004 kg, is stretched with a force. Calculate the force if the speed of the wave in the string is 140m/sec.  
• A note of frequency of 500 Hz is being emitted by an ambulance moving towards a listener at rest. If the listener detects a frequency of 526 Hz, calculate the speed of the ambulance. (speed of sound is 340 m/s at that moment).
• A simple pendulum completes 4 vibrations in 8 seconds on the surface of the earth. Find the time period on the surface of the moon where the acceleration due to gravity is one-sixth that of the earth.