Speed of sound, frames of reference

In summary, the speed of sound is relative to a stationary reference point is 330ms^-1 and relative to a moving reference point in the same direction as the speed of sound is equal to the speed of sound plus the velocity of the reference point. Conversely, the speed of sound relative to a moving reference point in the opposite direction is equal to the speed of sound minus the velocity of the reference point.
  • #1
saccapella
10
0

Homework Statement



[PLAIN]http://www.antonine-education.co.uk/Physics%20A%20level/Options/Module_8/Topic_6/cars_4.gif

What is the speed of sound, relative to:
A -
B -
C -

Homework Equations



None.

The Attempt at a Solution



For B, since B is a stationary reference point, the speed of sound relative to B should 330ms^-1

For A, I thought it should be 360, since A is a moving reference in the same direction as the speed of sound. Meaning A = 330+30=360

For C, I thought it should be 300, since the moving reference is moving in the opposite direction to the speed of sound, making B=330-30=300

My answers for A and C are wrong, however. Help!
 
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  • #2
Imagine that the sound is represented by a runner going at some velocity v. From A's point of view, will the runner be moving more quickly or more slowly?
 
  • #3
Slowly, right...?
 
  • #4
saccapella said:
Slowly, right...?

Right... so... what will be the speed of sound as "seen" by car A?
 
  • #5
300?
 
  • #6
saccapella said:
300?

Yup.

Now figure out what speed car C "sees".
 
  • #7
360...? Because the sound is towards C so the speed will 'seem' faster?
 
  • #8
I think you understand it well enough now to answer your own question :wink:
 
  • #9
Lol you're right on that :)
 

1. What is the speed of sound and how is it measured?

The speed of sound is the rate at which sound waves travel through a medium. It is typically measured in meters per second (m/s). The speed of sound can vary depending on the properties of the medium, such as temperature and humidity. For example, sound travels faster in warmer air than in colder air. To measure the speed of sound, scientists use equipment such as a microphone, speaker, and timer to measure the time it takes for a sound wave to travel a known distance.

2. What is the difference between the speed of sound in air and in water?

The speed of sound in air is much slower than in water. In air at room temperature, sound travels at approximately 343 m/s, while in water it can travel at around 1,484 m/s. This is because water is a denser medium than air, which allows sound waves to travel faster. Additionally, the speed of sound in water can vary depending on factors such as temperature, salinity, and depth.

3. How does the speed of sound change with altitude?

The speed of sound in air decreases as altitude increases. This is due to the decrease in air density at higher altitudes. As air becomes less dense, sound waves have less matter to travel through, causing them to slow down. At very high altitudes, such as in the stratosphere, the speed of sound can be significantly lower than at sea level.

4. What is the concept of frames of reference and how does it relate to the speed of sound?

The concept of frames of reference is an important concept in physics and refers to the perspective or point of view from which an observer is measuring an event or phenomenon. In terms of the speed of sound, different frames of reference can affect the perceived speed of sound. For example, if an observer is moving towards a sound source, they may perceive the sound to be traveling faster than an observer who is stationary.

5. Can the speed of sound be exceeded?

Yes, the speed of sound can be exceeded, but it is only possible in certain conditions. When an object is traveling faster than the speed of sound, it is said to be supersonic. This is commonly seen in objects such as fighter jets and bullets. However, it is important to note that the speed of sound is a limit for objects traveling through air. In other mediums, such as water, the speed of sound can be exceeded without causing a sonic boom or other effects.

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