Why/Does it take less force to unplug the cable if you pull it at a bigger lengths? I've tried many times and it seems so.
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3$\begingroup$ Have you done the experiment using a force gauge? $\endgroup$– John DotyCommented May 10, 2023 at 14:30
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$\begingroup$ No, just by feeling. $\endgroup$– sabilandCommented May 10, 2023 at 18:58
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26$\begingroup$ Friendly advice: Never pull the cable like this; it will damage the fragile junction between the wire and tip. You are supposed to pull it by the tip, not the wire. I have seen numerous cases where the junction is broken, and people end up cello-taping it. Why all those complications? Just pull it the right way. $\endgroup$– AlphaLifeCommented May 11, 2023 at 4:42
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3$\begingroup$ @AlphaLife: The garbage USB micro or C connector always wears out far before any damage from pulling becomes relevant. $\endgroup$– R.. GitHub STOP HELPING ICECommented May 11, 2023 at 13:35
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$\begingroup$ I know about never pulling cable like this:) This was just an example pic. $\endgroup$– sabilandCommented May 11, 2023 at 15:16
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4 Answers
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This is the same reason why longer screwdrivers are said to "produce more torque" when driving a screw. For the same angular deviation from the optimal axis, the longer the wire/screwdriver is, the more the deviation in distance from that optimal line.
That means with a longer screwdriver/wire, angular alignment is less sensitive to hand position while misalignment is also easier to detect. Pay very close attention to the exact motion, angles, and directions of your arm, hands, and fingers when pulling the cable out. Also, remember that the laptop port sits closer to the surface of the table than your hand is thick, and both your eyes and arms high above. Your misalignment is probably more up than sideways. Sideways misalignment is not the only misalignment possible; It's just the most visible from your eyes above.
At 2cm length, you might be pulling at 30 degrees and not notice. You would never do that when pulling at 30cm.
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$\begingroup$ I've thought for many years that a long screwdriver seems to do the job better than a short one. And I'm not sure it's down to angles. Too much of an angle with either will cause cam-out, which doesn't do/undo any screw. Even directly in line, the longer, the better. Not sure why though. Pulling a long wire: the plug will inevitably pull out straighter, even if the wire is at an angle to the port. $\endgroup$– TimCommented May 13, 2023 at 9:52
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$\begingroup$ @Tim It's essentially impossible for a human hand to turn a screwdriver in line so even if you can't perceive the difference in a long handle it should still be there. The only real way to test your hypothesis is to use a fixed stand that holds the screwdriver in line and remove angles from the equation. This becomes really obvious in things like test dial indicators when you are screwing in a new lever probe. it's impossible to tighten the probe in concentrically so that the indicator dial doesn't move. $\endgroup$– DKNguyenCommented May 13, 2023 at 17:04
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Another contributing cause is that the longer cable length results in a longer motion, if the cable is not taut when you start pulling - the hand, and the end of the cable have more time to accelerate. That is also why it is harder to put force in a short punch.
As Amit mentioned in their comment, depending on the proportion of the cable+connector assembly that is rigid - shorter rigid part decreases the contribution of pulling at an angle as the moment becomes smaller - the cable pulling at an angle creates a sideways force on the connector, which is larger the longer cable is as well as this effectively becomes a system of two levers once the cable is pulled taut.
There may also be an extra side effect, as the connector being pulled sideways causes it to jam against the socket, with more friction to overcome to pull this out. If the rigid part is short or nonexistent, both of those angle-based effects are a lot less pronounced, the angle still likely plays a part though, as determined by the vector math (which I am not good at) of forces involved.
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1$\begingroup$ I think that the correct answer is actually a combination of what DKNguyen pointed out and this answer. What determines the contribution of each I think, is the length of the connector's head which is rigid. Since it is rigid, the shorter this part is, perhaps the effect due to the additional acceleration becomes even more important than that of the misalignment... (suppose no rigid connector at all, I think the tension at the end of the cable will be determined only be the force/acceleration applied, regardless of where along the cable it was applied at) $\endgroup$– AmitCommented May 11, 2023 at 14:27
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1$\begingroup$ @Amit thanks for your comment, I agree there are multiple things at work here and I have edited my answer a bit to reflect on that, adding some more thoughts as well. $\endgroup$ Commented May 11, 2023 at 14:38
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$\begingroup$ Very interesting first point. With a sufficiently long cable, it's possible to unplug it using arbitrarily little applied force simply by accelerating your arm very gently over a long distance, and letting your arm's own momentum pull it out. There's a sudden jerk when the cable goes taut, not sure if that would be characterized as a "pulling" force, though. $\endgroup$ Commented May 12, 2023 at 16:04
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$\begingroup$ @NuclearHoagie somewhat different mechanics, but, again, with a sufficiently long (and heavy) cable you can yank it with a short but swift movement perpendicularly to the direction of the cable, which causes a wave to travel up the cable towards the other end and then that wave will apply the same force and pull the plug out as the wave starts reflecting back from the end of the cable. Oh, obviously, don't do that, lol $\endgroup$ Commented May 13, 2023 at 15:04
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I would suggest that the difference in force is just an illusion. If your hand grabs the cord from close up to the laptop, you're probably using minor muscles to pull the cord out. But if your hand grabs the cord from farther out and you pull, you're probably using major muscles to pull the cord out.
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2$\begingroup$ Hey Matt, your point is very interesting and what muscles are being used to pull the cable definitely have an impact on the perception of effort. However, there's a bit too much speculation on the first sentence. Let me show why I think it's speculation: We could do an experiment to see if OP's claim is valid. Measure the pull force at several lengths, plot a nice graph, etc. I don't think anyone did. So why do you believe it's an illusion? $\endgroup$ Commented May 12, 2023 at 14:37
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$\begingroup$ Hi @MindwinRememberMonica, of course it's speculation. In fact every answer here is going to be speculation because we don't have any evidence for how it is actually being pulled out. We don't know if there is a difference in the angle of pull, the grip, or if OP might even be holding it upside down when pulling. However, if I imagine myself pulling the cable from close up, I would use my fingers to pull. But if I were to pull from farther out, I would use more of my shoulder. $\endgroup$ Commented May 17, 2023 at 1:46
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It will actually take slightly more force to unplug a cable when the length is longer.
This is because the cable will stretch to some extent as it is pulled, even if that stretch is very minimal. The longer the cable, the more material there is to be stretched.
Note: This same stretch may make it feel like it takes less force to unplug a longer cable than a shorter one. As force is applied to the cable, it stretches, and then contracts. Thus the cable itself is "helping" to unplug the end from the socket.
If a force gauge were applied consistently to this question, I believe we would find that it takes more force to unplug a longer cable than a shorter one.
This is assuming a steady pull. If we're talking about a quick "yank" instead, then the stretch mentioned above might cause the longer cable to unplug with less force, due to the contraction of the cable after the yank. But some energy is going to be lost to friction, so even taking this into account the longer cable should still require more force to be unplugged.
