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Captain America's shield properties

  1. Mar 1, 2010 #1
    In comics, Captain America's shield can absorb an incredible amount of kinetic energy from impacts (if not all of it) because of its vibranium makeup. That is why he can block hits from super-strong beings like Hulk without any damage done to him or him going backwards. But when he throws the shield it bounces off walls and other targets with little to no speed loss.

    I have two questions:

    1. Is the shield's absorbing impact properties consistent or inconsistent with its minimal loss of speed when ricocheting?

    2. Does the shield's ability to bounce off its targets with little to no speed loss make its force of impact very great (which is the very reason why Captain America can hurt very durable beings like Hulk with mere shield throws)?
     
  2. jcsd
  3. Mar 1, 2010 #2

    Danger

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    The simple answer is that it's fiction, and not even hard SF at that. There is no science involved.
     
  4. Mar 1, 2010 #3
    In elastic collisions kinetic energy is conserved. And an object loses most of it energy when it collides with objects of similar mass. Like pool balls vs pool ball and pool rail. I expect most of the collisions the shield makes with foes are between two very different masses and hence the shield retains allmost all of it's initial energy. That's about all I can muster...
     
  5. Mar 2, 2010 #4

    Matterwave

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    I suppose the shield could be composed of molecules such that the energy from any impact forces greater than some threshold would be dispersed into the molecules making up the shield (making it a lot hotter o_O) through some, as yet, unknown mechanism. When Captain America throws the shield, he does not throw it with sufficient force that this threshold is reached, so the shield does NOT absorb all the energy of impact, and is allowed to ricochet elastically.

    There are, in fact, materials which harden when sufficient impact force is applied to them. You can try looking up these helmet beanies they have invented. Normally the beanies act like regular soft beanies, but when a sudden impact strikes them, they harden like helmets.

    So, it's not like this kind of material is completely inconceivable imo. However, it's still pretty far-fetched at this point.
     
  6. Mar 2, 2010 #5
    I'm not asking should the shield bounce back but should it bounce back at the same speed (or nearly).

    The shield practically bounces off at the SAME speed as it was thrown. It can richochet 100 times and still have nearly the same speed. Is this consistent to it being able to absorb kinetic energy from ALL impacts or contradictory to it?
     
  7. Mar 4, 2010 #6

    Matterwave

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    If it just absorbed all the kinetic energy from every impact, it will not bounce at all (ALL the energy it had would be absorbed, and there would be no energy left for motion).

    For it to bounce back at the exact same speed as it hit the wall, it would have to impart no energy to the wall, and it would not allow any energy to be dispersed into heat or sound, a case which is impossible. This is entirely incompatible with it absorbing all the energy from an impact. This is why I suggested that perhaps there needs to be a threshold force required before the shield will absorb the energy.
     
  8. Mar 4, 2010 #7
    I don't know much about Captain America, but with regards to your second question I would have thought it would be preferable for the shield to have as low a rebound speed as possible after hitting its intended target. This way, its kinetic energy must have been dissipated into said target, causing greater damage/injury.

    In summary, no. The fact that it bounces off shouldn't make the impact so great, it should in fact lessen its effects.
     
  9. Mar 4, 2010 #8
    I don't know much about Captain America, but with regards to your second question I would have thought it would be preferable for the shield to have as low a rebound speed as possible after hitting its intended target. This way, its kinetic energy must have been dissipated into said target, causing greater damage/injury.

    In summary, no. The fact that it bounces off shouldn't make the impact so great, it should in fact lessen its effects.
     
  10. Mar 5, 2010 #9
    Thank you! Now it makes since. That is what I figured but wasn't sure.
    The threshold theory could be right. Maybe after x distance of indentation the shields absorbing properties kicks in. < x distance means the shield just bounces back (doesn't absorb but acts like a spring).

    The only problem is that when the shield is thrown it is able to hurt even bullet proof beings like Hulk and such while bouncing off well. Maybe the kinetic energy it stored from previous impacts it actually released into the target it was thrown at. Is this feasible?
     
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