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d4rr3n
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I'm trying to understand by what mechanism a whip can multiply the velocity of the initial arm motion until it reaches the speed of sound, how is it doing this?
How does a whip break speed of sound?
- Thread starter d4rr3n
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- Break Sound Speed Speed of sound
In summary, the phenomenon of a whip cracking at supersonic speeds can be explained by the decreasing diameter of the whip, which results in the same energy being distributed over a smaller mass. This leads to an increase in speed as the whip becomes thinner, eventually reaching speeds greater than the speed of sound. This is confirmed by both experiments and models. The crack of a whip comes from a loop traveling down the whip, gaining speed until it exceeds the speed of sound and creates a sonic boom. This phenomenon can be seen in slow motion videos, where the radius of the loop decreases as the speed increases. This can also be explained by the physics of whipcracking, where the supersonic speed of the tip is a result of a chain reaction of
- #2
mathman
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The end of the whip traces out a much longer distance than your arm, when going through one pass.
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nasu
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It has to do with the decreasing diameter of the whip, from the thick rope at the handle side to the very thin strands at he tip.
But the models to explain the details are not trivial.
A hand-waving explanation is the conservation of energy approach. As the whip becomes thinner, the same energy is distributed over a smaller mass so the speed of the whip particles increases. This is not wrong but it seems not to be the complete story.
But the models to explain the details are not trivial.
A hand-waving explanation is the conservation of energy approach. As the whip becomes thinner, the same energy is distributed over a smaller mass so the speed of the whip particles increases. This is not wrong but it seems not to be the complete story.
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d4rr3n
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I have been watching slow motion videos of whips cracking and the tip makes a loop traveling at speeds above that of sound. I was thinking it might be due to centripetal acceleration. The radius of the loop decreases as it travels down the whip.
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The mass m of the whip's part of the line which wants to become straight (the rest) is proportional to its length L. With L converges m to zero at constant kinetic energy E = 1/2·m·v². Due to energy conservation v increases to ∞. For practical reasons v is bounded but big enough to break the sound barrier.
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d4rr3n
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I have found that you can easily crack a leather cord with no tapering, therefore the belief that the phenomenon is due to the mass variance along the length of the whip is incorrect.
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nasu
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Your "therefore" does not follow.d4rr3n said:
You can produce sound in many different ways. Most of them do not involve supersonic speeds.
If you look through the papers about the physics of the whip crack, you will see that the necessity of having supersonic speeds is not completely confirmed or accepted.
However the motion at speeds over speed of sound seem to be confirmed by both experiments and models.
The OP question was about what mechanism can explain the supersonic speeds and not about the relationship between these speeds and the whip crack.
- #9
d4rr3n
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True Cause of Whip's Crack Uncovered
http://www.scientificamerican.com/article/true-cause-of-whips-crack/
In the above they are saying it is not the tip that brakes the speed of sound but it is the loop traveling down the whip which is accelerating until it exceeds the speed of sound.
"The crack of a whip comes from a loop traveling along the whip, gaining speed until it reaches the speed of sound and creates a sonic boom,"
In the video I posted you can see the loop that they are talking about and you can also see that the radius of the loop is decreasing as the speed is increasing.
http://www.scientificamerican.com/article/true-cause-of-whips-crack/
In the above they are saying it is not the tip that brakes the speed of sound but it is the loop traveling down the whip which is accelerating until it exceeds the speed of sound.
"The crack of a whip comes from a loop traveling along the whip, gaining speed until it reaches the speed of sound and creates a sonic boom,"
In the video I posted you can see the loop that they are talking about and you can also see that the radius of the loop is decreasing as the speed is increasing.
- #10
ycc_swe
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Here is an essay treating the physics of whipcracking. It explains the supersonic speed of the tip of the whip as a result of "a chain reaction of levers and blocks".
http://whip.creatingspeed.com
http://whip.creatingspeed.com
1. How does a whip break the speed of sound?
A whip is able to break the speed of sound by creating a sonic boom, which is a loud noise caused by the sudden release of pressure built up from the whip's movement. When the whip is cracked, the tip of the whip moves faster than the speed of sound, creating a small sonic boom.
2. What causes the sonic boom when a whip is cracked?
The sonic boom is caused by the whip's tip moving faster than the speed of sound, creating a shockwave that travels through the air. This shockwave creates a sudden change in air pressure, resulting in the loud noise we hear.
3. How does the whip's tip move faster than the speed of sound?
When a whip is cracked, the handle is moved quickly, which creates a wave that travels down the length of the whip. This wave causes the tip of the whip to move at a high speed, breaking the sound barrier.
4. What factors affect the speed at which a whip breaks the sound barrier?
The main factor that affects the speed at which a whip breaks the sound barrier is the length of the whip. A longer whip will have a longer wave and therefore be able to reach higher speeds. The material and flexibility of the whip also play a role in its speed.
5. Is it dangerous to crack a whip and create a sonic boom?
Cracking a whip and creating a sonic boom can be dangerous for both the person cracking the whip and those around them. The sudden release of pressure can cause damage to the ear and hearing, and the whip itself can cause injury if not used properly. It is important to take precautions and be trained in proper whip cracking techniques before attempting to break the speed of sound with a whip.