Timeline for If vibranium absorbs kinetic energy, how can Captain America hurt people with his shield?
Current License: CC BY-SA 3.0
26 events
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| May 16, 2016 at 18:28 | comment | added | Thaddeus Howze | I like this answer SO much. I never considered the idea of the shield's movement being conserved through the action of the vibranium and the shield moving state. It also makes sense why it could deflect things when Cap is standing still and yet with the right motion capable of bouncing bullets or blasts to other targets. When the shield is at rest, it causes any action against it to remain 'at rest'. When the shield is in motion, it tends to stay in motion unless a target absorbs the shield's moving energy; i.e. hitting the Blob's belly, for example. It wouldn't bounce, it would just drop... | |
| May 19, 2015 at 18:17 | history | edited | Omegacron | CC BY-SA 3.0 |
fixed a typo, changed "at it" to "into it"
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| May 12, 2015 at 9:55 | comment | added | Mast | Of-course, our current understanding of physics might be flawed. Although I'm not sure how making our current physics model less reliable improves the reliability of comic book physics, it should be noted that Newtonian physics are quite old and may collapse after research. | |
| May 9, 2015 at 16:31 | comment | added | Ajedi32 | In regards to the idea of the shield being "polarized" maybe the shape of the shield has something to do with it. Combined with the properties of vibranium, perhaps the curved shape of the shield results in more of the energy from impact being directed towards the front of the shield, regardless of which side the impact strikes from. | |
| May 9, 2015 at 2:23 | comment | added | Trisped | It is also important to remember that for every force there is an opposite force. This means that when the object applies a force to the shield, the shield applies that force back, resulting in both the object and the shield experiencing the same impact. The shield has the advantage because it can withstand massive impacts (durable) and because it does not transfer the energy of the impact to other objects. The physics are actually pretty simple, it is just the magic of the absorption which cannot be explained. | |
| May 9, 2015 at 2:20 | comment | added | Trisped | The ratio of absorbed/converted energy might scale up with the amount of energy. The harder the hit, the higher the % of energy is that is absorbed. This would make the shield easy to move (since there is a low, continuous/long acceleration) and great at absorbing impacts (since there is a high, instant/short acceleration). | |
| May 8, 2015 at 18:06 | history | edited | Omegacron | CC BY-SA 3.0 |
added 397 characters in body
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| May 8, 2015 at 18:02 | comment | added | user31178 | @Hypnofisl I think maybe the physics of super strength in Marvel deserve their own question. | |
| May 8, 2015 at 18:01 | comment | added | Hypnosifl | @CreationEdge - Good point about Cap getting pushed back in mid-air. As for the rest, I assumed that super-strong characters either had much more mass, or their muscles could twitch at super fast velocities--I can't think of specific examples of feats of strength, but doesn't Thor sometimes punch through very solid-seeming objects or hurl very heavy objects, suggesting great momentum? But Cap also has a form of super-strength so I guess it's possible that lets him channel large incoming momentum through his body into the Earth without breaking bones--but if so, how is the shield helping? | |
| May 8, 2015 at 17:53 | comment | added | Wad Cheber | @Hypnosifl - A bit like the Planet Express ship on Futurama, which has engines that move the universe while the ship sits still | |
| May 8, 2015 at 17:51 | comment | added | Wad Cheber | @Hypnosifl - I had a similar thought, i.e. absorbing all kinetic energy = immovable object. In which case it could work by anchoring Cap so that it looks like he's throwing the shield, but really, the shield is remaining stationary and he is moving the entire universe in such a way that the bad guy is being pulled towards the shield at high speed. | |
| May 8, 2015 at 17:46 | comment | added | user31178 |
@Hypnosifl I'm not sure the momentum example is even a concern. The system in your example would be Cap MV_0 == 0 and Thor MV_0 > 0. But the two have similar masses, and Thor's punch doesn't necessarily have such high magnitude V that it trumps Cap's Super Serum body. Also, we see in The Avengers during the Battle of New York that when Cap is mid-air and a force meets his shield he does get blown back (see the scene in the building when a Chitauri grenade launches Cap out a window.)
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| May 8, 2015 at 17:46 | comment | added | Hypnosifl | Well, I'm not really asking you to come up with a good explanation for this, just making the rhetorical point that this is pretty much impossible to explain in terms of any real physics principles so the best answer is just "comic book physics". Probably the closest you could come to a more coherent answer would be to say the kinetic energy and momentum are being shunted off to another dimension (the same one The Hulk gets his extra mass from?), and that this shunting only works in one direction, so when Cap pushes the shield from behind it doesn't get shunted. But no canon support for this... | |
| May 8, 2015 at 17:35 | comment | added | Omegacron | @Hypnosifl : ... you guys are killing me here. | |
| May 8, 2015 at 17:31 | comment | added | Hypnosifl | What about conservation of momentum? If Thor's fist comes in at the shield in a leftward direction, then if the shield stops his fist, the shield itself must gain the same momentum to the left, and if it doesn't go flying that must be because Captain America planted his feet in the ground and the momentum was transferred through his body to the Earth. But whatever momentum mv it initially gains before Cap has time to decelerate it (equal to the momentum MV of Thor's punch), it must transfer kinetic energy (1/2)mv^2 to Cap, there isn't really any way to get around this in Newtonian physics. | |
| May 8, 2015 at 17:20 | comment | added | Omegacron | I added a section about the Third Law, you guys. Yeesh. | |
| May 8, 2015 at 17:20 | history | edited | Omegacron | CC BY-SA 3.0 |
added Third Law section
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| May 8, 2015 at 16:53 | comment | added | njzk2 | you can't have newton's first law without newton's third law... | |
| May 8, 2015 at 15:12 | comment | added | Hypnosifl | ...basically, I think we should just leave it at the last line of your answer (or KSmart's comment above)--it's comic book physics, any attempt to analyze it in terms of real physical principles isn't going to work. | |
| May 8, 2015 at 15:09 | comment | added | Hypnosifl | If it prevents kinetic energy from being transferred through it, shouldn't that apply to the kinetic energy of Captain America's own arm when he tries to move the shield? If he hits someone in the face with the front of the shield, didn't the kinetic energy they feel from the shield have the origin in his arm movement? Or if you say that's a case of kinetic energy being "transferred out of it", then why doesn't it work from front to back (Thor hits front, shield transfers kinetic energy to Cap's arm) as it does back to front (Cap pushes out with arm, front of shield transfers KE to villain)? | |
| May 8, 2015 at 14:44 | comment | added | user16696 | Every action has an equal an opposite reaction. That's what recoil is. A gunshot causes the same energy to go into the gun as it causes to go into the bullet out into the target. And relativity would tell us that there is no difference between the moving shield hitting a non moving person as a moving person hitting the shield. | |
| May 8, 2015 at 14:37 | comment | added | Clyde | You do have some good information in your post, and I do get it's a comic book world too. >.< Frustrating indeed. Thumbs Up! | |
| May 8, 2015 at 14:23 | comment | added | Clyde | The only problem with "directed at it" is I don't think it is worded correctly. If a someone with a bat hits my shield it absorbs kinetic energy, but if I hit my shield against a bat with the same force it doesn't? Force isn't just one way, every time something has force acted on it, it "pushes" back with force. If it pushes back equally nothing happens and if it pushes back with less it moves. | |
| May 8, 2015 at 14:13 | history | edited | Omegacron | CC BY-SA 3.0 |
added image
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| May 8, 2015 at 14:07 | history | edited | Omegacron | CC BY-SA 3.0 |
changed some links, added more
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| May 8, 2015 at 13:56 | history | answered | Omegacron | CC BY-SA 3.0 |