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Jab or follow through on punch?

  1. Dec 4, 2006 #1
    i've heard that if you are a boxer or pugnacious in general you should follow through on your punch. but in light of the fact that Impulse= F*T=m*V
    isnt it better to jab since as time of collision is small (during a jab compared to a punch you follow through on) F will be larger than if you followed through-because then time would be relatively larger and so F applied will be larger???this all assumes m*v = costant of course.

    i just want to know which method do you use to apply a larger force?
    i know there are good reasons and a time and a place for punching rather than jabbing but i just want to know which way applies a larger force on your opponent?


    thanks
     
  2. jcsd
  3. Dec 4, 2006 #2

    berkeman

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    The force F is not determined by the time, so don't try to claim increasing force with shorter times. The fist is driven, not bouncing independently. The follow-through ensures a longer contact time with the relatively constant punching force, thus transferring more energy. The reason to jab instead of follow through has to do with leaving youself exposed for a counter punch. You jab when you're worried about a counter punch.


    EDIT -- amazing the things you learn on the PF, eh?
     
  4. Dec 4, 2006 #3
    You have what you're body is doing backwards. Your body is exerting the force, through your fist, so exerting that force for a longer period of time leads to a larger impulse, which is what you want.
     
  5. Dec 4, 2006 #4
    Being an experimentalist and having boxed and all... How many times have you seen someone knocked out with a jab vs with a right cross?
     
  6. Dec 4, 2006 #5
    as a tae kwon do black belt, i say follow through punch

    as an amateur physicist, I would agree with those who say a jab wouldn't be as strong (unless you are sliding forward while you jab) because of the way you jab. some of the force that you put into your jab will be neutralized and taken off of your opponent when you pull your hand away, and the energy goes backwards into your shoulder, while in a follow through punch, your whole body continues forward until your fist has gone through, meaning none of the force is expended into ending your punch, and you have the full force of your lower body constantly adding momentum even after you make contact
     
  7. Dec 4, 2006 #6
    Well, however this works in real life, im not sure.

    But at least from a physics standpoint, don't follow through. If you follow, through, you will have to exert a force on a punch, and exert a force stopping the punch. If you jab, you will only have to exert a force on the punch....the opponent will stop your punch, thereby saving you some energy.

    You'll get tired less quickly if you jab. In theory, at least.
     
  8. Dec 4, 2006 #7

    Hurkyl

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    You'll get tired even less quickly if you don't punch at all. :tongue:
     
  9. Dec 5, 2006 #8

    berkeman

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    Well, then learn from the people who posted above you who do know how it works in real life and in physics. As you study more physics, you'll start to see why the follow-through punch delivers more energy. Welcome to the PF, BTW.
     
  10. Dec 5, 2006 #9
    ok now im confused.let me see if i have this right
    true or false if
    Impulse=change in momentum = m*Vf-Vi= F*T
    then IF impulse = constant than as T-time of impact goes down F goes up do i have that right?

    but in this case people are saying that F is constant basically.
    so if youre trying to hit something or someone you dont really care about applying a larger FORCE but rather a larger IMPULSE(change in momentum)?-and this hurts more if youre hitting someone.

    basically force is not the fundamental quantity of interest it is the impulse in this case? right?
     
  11. Dec 5, 2006 #10

    berkeman

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    No. The thing you are missing is that a follow-through punch has near constant force throughout. The fist is not a free body. Do you see how that changes the math?
     
  12. Dec 5, 2006 #11

    Danger

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    I have no formal training of any sort, but my informal advice was always: if you want to hit the guy on the jaw, aim for the back of his head.
    The physics part of it has been adequately explained, but there's also a psychological component. There is a tendency to 'pull' a punch as it reaches the target, which an untrained combatant has trouble overcoming. I think that it has to do with not wanting to hurt your hand. If you aim to punch through the target, all of your force will be expended upon it.
     
  13. Dec 5, 2006 #12
    yeah i understand that as i said " but in this case people are saying that F is constant basically. " so what in my summary is incorrect?
    i am not asking about why/when/how one should jab or follow through.
    i was just asking about what applies a larger force and now i see that a jab and a follow through apply the same force basically but we dont care about that because we really want to apply a larger impulse to our opponent?
    right?
     
  14. Dec 5, 2006 #13

    berkeman

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    Upon further review, I guess your statements were okay. The thing that confused me is when you mixed in this statement:

    which we had already discounted as not applicable to this scenario. But then I missed where you went on to discount it as well.
     
  15. Dec 5, 2006 #14

    depends on the way you follow through, if you follow through all the way you will most likely do a small circular motion when you take your arm back, which turns some of the excess force into turning your chest back into the right position as it was in befor you punched, as opposed to a jab where there is no circular motion and its all straight forwards and backwards.

    welcom to pf
     
  16. Dec 13, 2006 #15
    They probably say that so that you get use to exerting those muscle grps at full power and exertion like training for a high jump, but since I do some amatuer boxing I also know that speed is just as important and agree that a faster hit delivers more burst force but less overall force which is like a whip you can slice skin with it even though it doesn't have the same throwing someone back and rattling their cage effect.
     
  17. Dec 13, 2006 #16

    Danger

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    From a total outsider viewpoint (and this just occurred to me this minute, with a ****load of beer behind it), I would think that a 'jab' would be a good stun manoeuvre, whereas a good solid follow-through is the knock-out type. If you jab somebody upside the head enough times, you should have more than enough time to present the roundhouse and put him down. I know that there's something wrong with that analysis, but I'm too drunk to figure it out. :redface:
     
  18. Jan 2, 2007 #17
    Hello, I recently discovered this forum while searching for a force meter for measuring impulse from a punch. I also found the following article that people here might find interesting:

    From http://www.physicsclassroom.com/Class/momentum/U4L1c.html

    Fans of boxing frequently observe this same principle of minimizing the effect of a force by extending the time of collision. When a boxer recognizes that he will be hit in the head by his opponent, the boxer often relaxes his neck and allows his head to move backwards upon impact. In the boxing world, this is known as riding the punch. A boxer rides the punch in order to extend the time of impact of the glove with their head. Extending the time results in decreasing the force and thus minimizing the effect of the force in the collision. Merely increasing the collision time by a factor of ten would result in a tenfold decrease in the force. Now that's physics in action.

    So summarize: If you throw a punch, without follow through, and it bounces as fast as a jab, then the impulse was very high. If you throw a punch and exert energy to withdraw your fist before reaching the point where your opponents head would have fully stopped the blow then you have WASTED IMPULSE engery becuase you worked to counter it. If you throw a punch and follow through then your opponent not only feels the full punch but added to that all of the energy you could impart after point of impact...

    If anyone knows where I can get a device for measuring impulse energy of a fist I would be interested: powell(dot)sean(at)comcast(dot)net

    Thanks, Sean
     
  19. Jan 2, 2007 #18

    turbo

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