From: se020151@seas.gwu.edu (Hyok Lee)
Subject: Re: strings
Organization: George Washington University
Date: Fri, 17 Apr 1992 05:40:38 GMT


lfd@cbnewsm.cb.att.com (Lee Derbenwick) writes:
: In article <1992Apr15.180031.7899@news.iastate.edu>,
: whisnant@iastate.edu (Kerry L Whisnant) writes,
: in response to my posting:
: 
: [ a nice, very detailed  analysis ]
: 
: > From these equations it is clear that increasing k (i.e., the tension):
: > 
: > 1. Decreases the time on the racquet
: > 2. Decreases the final ball speed
: > 3. Increases the maximum force on the ball
: > 
: > Thus tighter strings touch the ball a shorter time and give less
: > power, but the maximum force on the ball is greater.
: 
: This then led to the apparent result that the looser strings give
: more spin, unless the friction increases (significantly?) more than
: linearly with the normal force.
: 
: I suspect that the friction does increase more than linearly (the
: analysis ignored ball deformation), but it may not do so enough
: to completely counter the extra time on the looser strings.
: 
: But let's look at the case where the final velocity, rather than
: the applied force, _is_ kept the same.  This should be the case
: with a drop volley or other touch shot, since the player is trying
: for placement and speed.  In that case, the average applied force
: must be greater for the tighter racquet (my own initial analysis).
: So the peak force will be proportionally still greater.
: 
: That combination (along with any contribution from ball deformation)
: should make the tighter strings provide more spin for touch shots.
: 
: So it's starting to look like the looser strings provide more
: power and more spin for all-out, hard hits, but the tighter strings
: provide more spin for touch shots.
: 
: Carrying out this analysis in more depth might make a good physics
: project for someone, especially combined with some experiments to
: validate the assumptions...
: 
:  -- Speaking strictly for myself,
:  --   Lee Derbenwick, AT&T Bell Laboratories, Warren, NJ
:  --   lfd@cbnewsm.ATT.COM  or  <wherever>!att!cbnewsm!lfd
 I think that you are right in suggesting that only a carefully carries
out experiment can confirm this.  I can only say that I feel more
spin with loose strings.  I just keep on thinking that after a certain
point, the increase in normal force cannot add to greater spin, because
after a certain critical normal force, more increase in force will not
contribute to more spin.  I am also a table tennis player and evryone in
the world now plays with a sandwich bat because the extra cushioning
effect from the sponge provides more spin because the ball stays in
contact longer.  In fact, the thichness of the sponge is limited by
international rules.  I don't know if the same principle translates into
tennis, but that my line of reasoning.
.
--
     ***************************************************************
     * Hyok Lee    George Washington University, SEAS              *
     *                                                             *
     * Ddong ssan nom eun domang ga go, bangoo ggeen nom ee        *
     *      japyot da.                                             *.
     *                           -Korean proverb.                  *
     *                                                             *
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