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abcd8989
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Why a rubber band gets warmer when repeatedly stretched and relaxes? Where does the gained ME comes from? Besides, does rubber band obeys Hooke's Law?
Mapes said:Any temperature increase after stretching and releasing would be due to internal friction, from polymer chains moving past each other. And every solid obeys Hooke's Law for small enough deformations. Take a look at a stress-strain curve for rubber to see how its stiffness changes as you stretch it.
Oldfart said:I kinda thought it was due at least in part to thermodynamics. Try this: Get a largish rubber band, stretch it tightly (using both hands) while holding it against your upper lip. It will feel warmer right after the stretch. Now move the rubber band away from your lip but keep it stretched, hold it that way for maybe 30 seconds or so. Then hold it aginst your lip again and immediately relax the stretch and it will feel cool. The cooling wouldn't be due to friction, right?
Dickfore said:No, and the question you had asked does not correspond to reality. If you relax a stretched rubber band it should cool.
The physics behind stretching a rubber band is based on the concept of elasticity. Rubber bands are made of long chains of molecules that can stretch and return to their original shape. When a rubber band is stretched, the molecules are pulled apart, but they still want to return to their original state. This creates a force known as tension, which causes the rubber band to resist the stretching and eventually return to its resting state.
A rubber band becomes harder to stretch as it is stretched further because the tension force increases as the molecules are pulled further apart. This increase in tension is due to the fact that the molecules are being stretched closer to their breaking point, making it more difficult to continue stretching the rubber band.
Yes, there is a limit to how far a rubber band can stretch. This limit is known as the elastic limit and it is the point at which the rubber band can no longer return to its original shape. If a rubber band is stretched beyond its elastic limit, it will permanently deform or break.
Temperature can affect the stretching of a rubber band in two ways. Firstly, at higher temperatures, the molecules in the rubber band have more energy and are able to stretch further before reaching their elastic limit. On the other hand, at lower temperatures, the molecules have less energy and are more tightly bound, making it harder to stretch the rubber band. Secondly, extreme temperatures, whether hot or cold, can cause the rubber band to lose its elasticity over time, making it less stretchy.
When a rubber band is stretched, it stores potential energy in the form of tension. This energy is stored in the bonds between the molecules that are being pulled apart. When the rubber band is released, this potential energy is converted into kinetic energy as the rubber band returns to its original shape. This is why a stretched rubber band will snap back quickly and with force when released.