GrandMasterK Posted October 26, 2015 Posted October 26, 2015 I was staring at the hook in the wall that holds up my guitar and I noticed over time it has gradually started pealing at the top. It occurs to me that the weight of the guitar is very gradually pulling the hook out of the wall and may very well collapse years from now. So it got me wondering.......when you hold something up, force is being applied constantly. Does that mean energy is being used constantly to hold the guitar up? Or am I thinking about it wrong?
swansont Posted October 26, 2015 Posted October 26, 2015 If there is no motion, there is no energy involved because the work done is zero. It's completely static. That's the idealized version. However, in real-world situations, there is motion — there's vibration going on, both microscopic and macroscopic. So you are doing work on that scale, and breaking bonds between atoms and breaking down whatever structure is in the material. You will eventually reach the point where the wall/hook can't exert the force it needs to. 1
GrandMasterK Posted October 26, 2015 Author Posted October 26, 2015 It is constantly exerting a force though yes? Does that require energy? Can you harness energy from a situation like that?
swansont Posted October 26, 2015 Posted October 26, 2015 It is constantly exerting a force though yes? Does that require energy? Can you harness energy from a situation like that? It requires motion for work to be done. That's the only way to harvest mechanical energy.
MigL Posted October 26, 2015 Posted October 26, 2015 One way to look at it is that the hook/guitar system has potential. Over time all the factors Swansont has mentioned degrade the stickiness of the hook. When it finally lets go, the potential is turned into motion as the guitar and hook fall to the ground under the influence of gravity. We can, then, harvest this kinetic energy, and use it to do work.
robinpike Posted October 28, 2015 Posted October 28, 2015 I was staring at the hook in the wall that holds up my guitar and I noticed over time it has gradually started pealing at the top. It occurs to me that the weight of the guitar is very gradually pulling the hook out of the wall and may very well collapse years from now. So it got me wondering.......when you hold something up, force is being applied constantly. Does that mean energy is being used constantly to hold the guitar up? Or am I thinking about it wrong? It requires motion for work to be done. That's the only way to harvest mechanical energy. Work has a very specific meaning with regards to energy - but the question was not whether the hook is doing work to stay up - but rather is the hook expending energy to stay up? What is the proof that the hook is NOT expending energy in order to stay put?
swansont Posted October 29, 2015 Posted October 29, 2015 Work has a very specific meaning with regards to energy - but the question was not whether the hook is doing work to stay up - but rather is the hook expending energy to stay up? What is the proof that the hook is NOT expending energy in order to stay put? "Expending energy" and "work" are synonymous for mechanical systems. There is no other path. 1
GrandMasterK Posted November 20, 2015 Author Posted November 20, 2015 I'm still kinda confused. The hook is using energy to keep the guitar from falling isn't it? Or at least the wall or glue that's keeping the hook from falling? If it were a person, we'd be using energy to hold it up or our arm would fall no? Doesn't the same go for an object preventing another object from moving? Like if I were pushing on somebody to keep them from moving forward or even just a wall that I'm leaning on? Why is there no way to harness this in any fashion?
swansont Posted November 20, 2015 Posted November 20, 2015 I'm still kinda confused. The hook is using energy to keep the guitar from falling isn't it? Or at least the wall or glue that's keeping the hook from falling? If it were a person, we'd be using energy to hold it up or our arm would fall no? Doesn't the same go for an object preventing another object from moving? Like if I were pushing on somebody to keep them from moving forward or even just a wall that I'm leaning on? Why is there no way to harness this in any fashion? It takes energy to hold something up because parts of your arm are in motion continually. But you aren't doing work if the object isn't moving. There's no energy you can extract from it.
John Cuthber Posted November 21, 2015 Posted November 21, 2015 What is the proof that the hook is NOT expending energy in order to stay put? Hooks don't need batteries.
Endy0816 Posted November 21, 2015 Posted November 21, 2015 Can generate heat from deformation. Something like a heavily loaded wire coat hanger is probably easier to consider. It can't provide any more power though than if you simply dropped it. Same amount of potential energy converted over a longer span of time. On a more practical note you might want to consider reinstalling. Sounds like it wasn't in a stud. Fun to explore your own walls, especially if you make your own stud finder out of a couple permanent magnets and a couple of plastic bottle caps.
MigL Posted November 21, 2015 Posted November 21, 2015 They're only $20 at the hardware store ! What' re you Scottish ? ( I'm only kidding, Ophiolite )
Endy0816 Posted November 22, 2015 Posted November 22, 2015 Multifunctional, though I do have a number of redheads in my family...
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