Speed of Sound MCQs Quiz | Class 9
Test your understanding of the speed of sound for Class IX Science (Unit III: Motion, Force and Work). This quiz covers the meaning of speed of sound, basic factors affecting it like temperature and medium, and typical speed values in different states of matter. Complete the 10 questions below and click “Submit Quiz” to view your score and download the answer key PDF.
Overview of Speed of Sound
Sound is a mechanical wave that requires a material medium for its propagation. The speed of sound refers to the distance travelled by a sound wave per unit of time as it propagates through an elastic medium. It is denoted by ‘v’ and is calculated as the product of frequency and wavelength.
Factors Affecting Speed of Sound
- Nature of the Medium: Sound travels fastest in solids, slower in liquids, and slowest in gases. This is because particles in solids are packed closely together, allowing vibrations to transfer more quickly.
- Temperature: The speed of sound in a medium is directly proportional to the temperature. As temperature increases, the speed of sound increases. For example, sound travels faster on a hot summer day than on a cold winter day.
- Humidity: In air, the speed of sound increases with humidity because moist air is less dense than dry air.
- Pressure: Change in pressure has no effect on the speed of sound in a gas, provided the temperature remains constant.
Typical Values
It is helpful to know approximate values for the speed of sound in different media at room temperature (around 20-25 degrees Celsius):
| Medium | State | Approx. Speed (m/s) |
|---|---|---|
| Dry Air (20 C) | Gas | 344 |
| Water (Distilled) | Liquid | 1498 |
| Iron/Steel | Solid | 5000 – 6000 |
Quick Revision Points
- Speed of sound in vacuum is zero.
- Light travels significantly faster than sound (Speed of light is 300,000,000 m/s). This is why we see lightning before hearing thunder.
- Sonic Boom occurs when an object travels faster than the speed of sound.
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