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Baseball bat impact force

  1. Feb 15, 2010 #1
    So a friend and I started a debate over dinner, and no-one around here really wants to side with either of us, since neither of us has any concrete facts on the issue. The issue is this: Which would have a greater chance of causing a fatal impact on someone, a wooden bat or an aluminum bat. Grim topic, I know.

    At any rate, my argument is thus: since the aluminum bat is made of a thin metal wall and a hollow center, it would tend to flex during impact, increasing impact time. In the end, the energy imparted is greater (like a trampoline, but those aren't painful to jump on!), but since it is spread out over a comparatively longer time, it would cause less injury. Conversely, the wooden bat is more rigid(being solid) and connects with the target and rebounds quickly away, with a near zero length of impact. I am under the impression that injury is caused by sudden changes in velocity (not the fall that kills you, but the sudden stop!), and given a near zero time for a subject's velocity to change, it would almost certainly break in some painful way.

    That said, either construction bat would be lethal at any reasonable velocity, so we're talking borderline cases. Given a two subjects (lets say they're identical twins, fed exactly the same so their juicy skulls have grown in precisely the same manner) and two bats, one typical aluminum construction, and one typical wood construction, with the same mass, you hit each person in the head with the bats starting at 1mph and working your way up in 1mph increments until one of them suffers a fatal injury, which bat would be the culprit? None of this was outlined in our debate, however, I just came up with this for the sake of consistency.

    PS. Hello physics forum, hopefully this site can solve many debates!
     
  2. jcsd
  3. Feb 16, 2010 #2
    Even though this is a bit macabre, I'll offer my viewpoint on this :smile:.

    * I don't think any damage to either type of baseball bat is necessary in order to inflict a deadly blow on the human head.

    From pictures I have seen, the aluminium bats seem to have higher proportion of mass concentrated at one end, where it hits the ball.

    If you are assuming the same mass and the same ANGULAR speed for such bat, then I would say that the aluminium bat is more dangerous. The main reason being that it has more mass concentrated around the point of impact. Thus it has a higher kinetiv energy and is is also much stiffer in the region of impact.

    If the bats were equal in shape (assuming a homogeneous shell thickness for the aluminium bat), I think the difference would be very small in this application, but maybe slightly in favour of the aluminium bat, since it is stiffer.

    EDIT: I'm assuming that the aliminium bat actually creates a larger force over a shorter time span because of its higher stiffness. E.g. the higher pitched sound those bats make are an indication of this.

    Torquil
     
  4. Feb 16, 2010 #3
    As I understand it, the aluminum bats are more flexible, as it is that flexibility that causes the trampoline effect that propels the baseball further. Furthermore, I'm relatively certain that the weight distribution is comparable, as they have the same center of gravity (I work at sport chalet)
     
  5. Feb 16, 2010 #4
    Even if the aluminium one has a trampoline effect, it doesn't necessarily mean that wood deforms less. It might just mean that the aluminium, unlike wood, can bounce back in time to give the ball even more momentum. Wood might be as soft, depending on the aluminium thickness (which I don't know). Do you notice any deformation when pushing you thumb against the aluminium bat?

    Actually, we don't even know what's worse biologically. It isn't obvious that a skull acceleration of "a" over a time "t" is worse than "a/2" over a time "2t". This answer could be a surprise, for large accelerations.

    My guess is that the answer is not obvious, and we have to do experiments to find out... So maybe it is good that we dont know :smile:

    Torquil
     
  6. Feb 16, 2010 #5
    These are all very good points. I had a bunch of scientific facts to offer, but they have all pretty much been covered. I mean, you could even go as far as to say that the temperature on that day could affect one bat differently than the other. But if wood is less flexible, I would have to agree. The more force per unit time, the more damage. I actually have no idea whatsoever which bat would incur more damage. You know what though, something just dawned on me. Which part of the bat is being used to hit the head. I feel like if it is the end of the bat, the wood one would be better, but if it was the sweet spot, the metal would.
     
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