# Energy transfer

## Main Question or Discussion Point

I have two fishing lines that are of the same material but one has a larger cross sectional area than the other, which one will transfer energy faster? I am not a physics person so a simple amswer would be appreciated. Thanks

## Answers and Replies

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russ_watters
Mentor
Transfer energy to/from what?

From one end of the line to the other end

The thicker line will transfer energy from one end to the other more easily. If you're transferring energy via heat, the thicker wire will transfer more energy due to the larger cross-section. If you're sending electrical current through the line, the thicker wire will have less resistance.

Hope that helps.

I believe it does. That means with the larger fishing line I would detect the fishes strike faster than with the smaller line.

I believe it does. That means with the larger fishing line I would detect the fishes strike faster than with the smaller line.
Actually, I misinterpreted your question. The larger wire will be able to transfer energy easier, but I believe you're looking for which line will transfer the signal of the fish's strike faster. This is a bit more complicated, but I believe you'd also detect the fish's strike faster with a thicker line, because the thicker line would elongate less when it's pulled.

That is what I was looking for and thank you for your help.

For the same tension in the line, the speed of sound is higher in the cord with lowest linear density. Assuming the same material, the thin line will transmit a mechanical excitation faster. (If the fish applies the same tension...).

For the same tension in the line, the speed of sound is higher in the cord with lowest linear density. Assuming the same material, the thin line will transmit a mechanical excitation faster. (If the fish applies the same tension...).
While this is true, when would you actually feel the fish pulling on the rod? Probably not when the first signal reaches the end of the line, but later, after the line pulls with enough force for you to feel it.

While this is true, when would you actually feel the fish pulling on the rod? Probably not when the first signal reaches the end of the line, but later, after the line pulls with enough force for you to feel it.
This is quite irrelevant. The sensitivity threshold of the "detector" is the same in both cases.
Whatever force is applied by the fish, it "reaches" the other end slower on the thick cord.
The peak of the force pulse take the same time to travel as the minimum or any other value.
If, for example, the force at the "fish end" increases continuously, from zero to a maximum value (let say 1000 N), the "hand end" will experience the same thing, with some delay given by the travel time along the cord. The delay between the 1N values at the two ends (application and reception) is the same as the delay between the 500N values and so on.
This is of course true for a linear and non dispersive medium approximation.

The difference between the two cords is the maximum force that can be transmitted before the cord breaks.

You're assuming the fish can apply the same force in an equal amount of time on both strings. However, if you consider the elasticity of the strings, the fish would need to swim further and stretch the small string more before the "sensitivity threshold" is met, compared to a larger string. Compared to this delay, the delay due to the signal propagation speed is insignificant.

First off let me thank you for your input it is much appreciated. I am a fly fisherman and what I am trying to do is to determine which diameter of line would detect strikes from the fish faster, the smaller or larger. The faster I notice the strike, the more fish I have the opportunity to hook. Given that everything is equal, except the diameters of the lines, I am hearing that the smaller diameter would detect strikes faster. Thanks again

You're assuming the fish can apply the same force in an equal amount of time on both strings. However, if you consider the elasticity of the strings, the fish would need to swim further and stretch the small string more before the "sensitivity threshold" is met, compared to a larger string. Compared to this delay, the delay due to the signal propagation speed is insignificant.
The problem is not formulated in a very specific manner. The question was about the energy transfer from one end to the other.
I was thinking about a cord already under tension and applying a very short impulse at the fish end.

Your model is different, I understand. You assume the tension increasing slowly in the string, fish swims away, right?. The distance traveled by the fish until some threshold force is reached will be shorter for the thick cord. The calculations show that the time will be shorter too. I don't know what is the minimum tension that the fisherman can feel. But the time to reach maximum tension can be estimated for typical parameters. It is much longer than the transmission through line, you are right.