Timeline for If vibranium absorbs kinetic energy, how can Captain America hurt people with his shield?
Current License: CC BY-SA 3.0
11 events
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| May 16, 2016 at 21:14 | history | edited | Paul Draper | CC BY-SA 3.0 |
added 13 characters in body
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| May 16, 2016 at 18:10 | history | edited | Paul Draper | CC BY-SA 3.0 |
added 44 characters in body
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| May 11, 2015 at 18:50 | comment | added | Paul Draper | @Trisped, right. There is no way to completely resolve physics in this universe and that description. And without mechanical physics (a generalized description of how things move), an answer to the OP's question is "just 'cause". | |
| May 11, 2015 at 18:34 | comment | added | Trisped |
If the momentum energy must be transferred, then the shield would not be able to meet the definition: "transfers very little energy from each impact". You have found a physics theory which does not apply to our comic book material. If this was a real world material, the theory would be revised. In our case it is not, so the theory stands, we just do not apply it to the material in the story.
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| May 11, 2015 at 14:29 | comment | added | Paul Draper | @jpmc26, absorbing kinetic energy is the difference between inelastic and elastic collisions. Kinetic energy can be converted to non-kinetic energy. Momentum cannot be converted to non-momentum. Kinetic energy depends on the materials involved; momentum doesn't, which is why I mention it. | |
| May 11, 2015 at 7:28 | comment | added | jpmc26 |
In classical Newtonian physics, momentum is defined as p = mv. Kinetic energy is defined as k = 1/2 mv^2. "Absorbing" kinetic energy is equivalent to "absorbing" momentum. You can't vary one of these quantities without varying the other. Momentum will not be conserved if the total kinetic energy of the system is not preserved. Additionally, conservation of momentum only works for forces internal to a system; in @Trisped's examples, the Earth and atmosphere are considered external to the system.
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| May 10, 2015 at 2:57 | comment | added | reirab | @Trisped In all of the examples that you list, momentum is actually conserved. It's just being transferred to very large things (such as the Earth and/or its atmosphere,) resulting in a non-noticeable difference in velocity. Also, note that momentum is a vector quantity. An explosion radiating out in all directions produces a net momentum change of zero. | |
| May 10, 2015 at 2:21 | comment | added | Lightness Races in Orbit | Yeah I mean he just wouldn't be able to even move it if it absorbed all kinetic energy. | |
| May 9, 2015 at 5:44 | comment | added | Paul Draper | @Trisped, right, it can only be transferred. | |
| May 9, 2015 at 2:16 | comment | added | Trisped | Momentum can be absorbed/converted to another form. For example: electromagnetic locks, explosions, and gravity can change the momentum of objects. The important point is that total energy is conserved. | |
| May 8, 2015 at 23:44 | history | answered | Paul Draper | CC BY-SA 3.0 |