Sound Class 8 Numerical

In this post, we will solve Numerical problems based on the Sound chapter of class 8 science. Here, first we will go through required formulas & other related equations, and then attempt the numerical questions. Solution & answer is given for all the numerical questions.

Related Post: Light class 8 numerical solved

Formulas Used

Frequency = 1 / Time Period
f = 1/T

Time Period = 1/frequency
T = 1/f

Distance traveled by a sound wave = speed of sound x time duration

Frequency = number of oscillations per second

Time period = time required for a single oscillation

Sound Class 8 Numerical Questions and Answers [solved]

Example 1. An object is vibrating at 50 hertz. What is its time period?


If an object is vibrating at 50 hertz
50 = 1/T
=> T = 1/50 = 0.02 sec
Its time period will be 0.02 sec.

Example 2. 1 hertz is equal to how many vibrations per minute?


1 Hz= 1 vibration/second
1 minute=60 seconds,
hence 1 hertz = 60 vibrations /minute

Example 3: Lightning can be seen the moment it occurs. Paheli observes lightning in her area. She hears the sound 5 s after she observed lightning. How far is she from the place where lightning occurs? (speed of sound =330 m/s).


Distance=330 m/s x 5s
=1650 m

Example 4: A simple pendulum makes 10 oscillations in 20 seconds. What is the time period and frequency of its oscillation?


Time period = time required for one oscillation =20/10 s = 2 s
frequency = 1/Time Period = 1/2 = 0.5 oscillations/sec = 0.5 Hz

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