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#1
01-25-2019, 01:30 PM
 RitterSport Guest Join Date: Mar 2002 Posts: 2,933
Baseball physics question

It's a Friday afternoon (here in NY) and I'm not asking a question about the Jewish religion! Seems like those questions always turn up during the Sabbath.

Anyway, here's my question:

You have two batters, one is 100 lbs and one is 200 lbs. They both get the same weight bat up to the same speed when the ball contacts the bat. Same pitch, no air friction, etc. Does the ball go the same distance?

What about if one the lighter batter has freakishly heavy arms and the heavier batter has light arm, so that their arms weigh exactly the same, but their total body weight is still 100 pounds different. Does that affect the ball distance?
#2
01-25-2019, 01:38 PM
 Jonathan Chance Domo Arigato Mister Moderato Moderator Join Date: Apr 2000 Location: On the run with Kilroy Posts: 22,261
I'm thinking either one would likely hit a strong single to GQ.

Look at it go!
#3
01-25-2019, 01:41 PM
 RitterSport Guest Join Date: Mar 2002 Posts: 2,933
Quote:
 Originally Posted by Jonathan Chance I'm thinking either one would likely hit a strong single to GQ. Look at it go!
Man, I can't believe I posted that in ATMB. Thanks for moving it!
#4
01-25-2019, 01:50 PM
 running coach Arms of Steel, Leg of Jello Charter Member Join Date: Nov 2000 Location: Riding my handcycle Posts: 36,174
Power is generated by the legs, transferred to the torso then through the arms. Imagine how far you could hit the ball if you stood still and just swung the bat with only your wrists.
It's like cracking a whip.
#5
01-25-2019, 02:15 PM
 Barkis is Willin' Guest Join Date: Jan 2010 Posts: 6,295
If I understand the question correctly, you want to know if 2 different guys will hit a ball the same distance if literally the only variable is their weight. They generate the same bat speed, the pitch speed is the same, swing angle is on the same plane, both make contact on exactly the same part of the same bat. Distance is about exit velocity and there are a lot of variables that go into exit velocity. But weight of the guy swinging the bat isn't one. So yeah, they'll hit it the same distance.
#6
01-25-2019, 02:50 PM
 RitterSport Guest Join Date: Mar 2002 Posts: 2,933
Quote:
 Originally Posted by Barkis is Willin' If I understand the question correctly, you want to know if 2 different guys will hit a ball the same distance if literally the only variable is their weight. They generate the same bat speed, the pitch speed is the same, swing angle is on the same plane, both make contact on exactly the same part of the same bat. Distance is about exit velocity and there are a lot of variables that go into exit velocity. But weight of the guy swinging the bat isn't one. So yeah, they'll hit it the same distance.
Yes, that is my question. And I know that, for all practical purposes, bat speed is all that matters. But, this is a physics question, not a baseball question.

I'm not saying you're wrong, but does the momentum of the bat holder matter at all, even theoretically? Or, is the bat (and arms?) effectively decoupled from the body holding it? Would it then not matter if the batter let go of the bat an instant before it struck the ball (so the bat speed is still the same)?
#7
01-25-2019, 03:30 PM
 Telemark Charter Member Join Date: Apr 2000 Location: Again, Titletown Posts: 21,986
https://www.acs.psu.edu/drussell/bats/impulse.htm

The inputs are just weights and speeds of the bat and ball. Essentially, the batter is only interesting in that he or she gets the bat up to speed. For a collision that lasts .7 milliseconds, the bat is essentially unanchored object.
#8
01-25-2019, 03:48 PM
 RitterSport Guest Join Date: Mar 2002 Posts: 2,933
That's what I suspected. Thanks for the cite!
#9
01-25-2019, 03:56 PM
 Chronos Charter Member Moderator Join Date: Jan 2000 Location: The Land of Cleves Posts: 81,351
Speaking abstractly, the bat would be almost like an unanchored object, but the batter is still exerting some nonzero force, and imparting some nonzero work, during the brief duration of the collision, so there would be some slight advantage to the bigger batter.
#10
01-25-2019, 04:06 PM
 CookingWithGas Charter Member Join Date: Mar 1999 Location: Tysons Corner, VA, USA Posts: 12,818
Quote:
 Originally Posted by Chronos Speaking abstractly, the bat would be almost like an unanchored object, but the batter is still exerting some nonzero force, and imparting some nonzero work, during the brief duration of the collision, so there would be some slight advantage to the bigger batter.
If he is also stronger.
#11
01-25-2019, 04:19 PM
 RitterSport Guest Join Date: Mar 2002 Posts: 2,933
Quote:
 Originally Posted by CookingWithGas If he is also stronger.
Right. Let's hold their strengths equal. All is equal except weight.
#12
01-25-2019, 09:19 PM
 DSYoungEsq Member Join Date: Jul 1999 Location: Indian Land, S Carolina Posts: 14,122
In my mind, answering this question, I think about the following scenario:

1) A bat is swung to hit a pitch, but the mechanism holding the bat has a relatively loose grip, and, upon contact, the bat is knocked out of the grip.

2) A bat is swung to hit a pitch, and the mechanism holding the bat has a relatively strong grip, and, upon contact, the bat is firmly kept in the control of the mechanism and continues on the swing plane.

In my estimation, the ball should go farther in 2 than in 1. That seems to indicate that, to the extent "power" is involved between our batters, the question is the ability of the batter to power the bat through the interaction with the ball. Weight alone won't do that.
#13
01-25-2019, 10:05 PM
 MrKnowItAll Guest Join Date: Mar 1999 Location: Cincinnati, Ohio Posts: 1,701
I think all other things being the same (skill/power/pitch) the heavier player will hit it slightly further, due to the fact the that the larger mass will resist being pushed backwards by the ball. The difference will be negligible.
#14
01-25-2019, 10:14 PM
 Ike Witt Friend of Cecil Charter Member Join Date: Aug 1999 Location: Lost in the mists of time Posts: 14,227
Quote:
 Originally Posted by DSYoungEsq In my estimation, the ball should go farther in 2 than in 1. That seems to indicate that, to the extent "power" is involved between our batters, the question is the ability of the batter to power the bat through the interaction with the ball. Weight alone won't do that.
I'm not so sure. The notion of powerful athletes having 'soft hands' comes from somewhere. Golf instructors will tell you to just let the club sit in your hands rather than grip it.
#15
01-25-2019, 11:25 PM
 Robot Arm Guest Join Date: Jun 2000 Location: Medford, MA Posts: 23,214
Quote:
 Originally Posted by MrKnowItAll I think all other things being the same (skill/power/pitch) the heavier player will hit it slightly further, due to the fact the that the larger mass will resist being pushed backwards by the ball. The difference will be negligible.
Any energy that goes in to making the bat rotate after the collision is energy that doesn't go into making the ball travel. The tighter a grip the batter has, or the heavier his forearms, the less energy is lost to the bat.

But it also depends where the ball hits the bat. If the path of the ball at the point of contact passes through the CG of the bat, then the collision will slow the bat but won't impart any force that causes it to rotate. In that case, the weight or grip of the batter doesn't matter.
#16
01-26-2019, 12:50 AM
 DSYoungEsq Member Join Date: Jul 1999 Location: Indian Land, S Carolina Posts: 14,122
Quote:
 Originally Posted by Ike Witt I'm not so sure. The notion of powerful athletes having 'soft hands' comes from somewhere. Golf instructors will tell you to just let the club sit in your hands rather than grip it.
A golf club is substantially different from a baseball bat (for reasons that should be obvious), and trust me, as one who has played golf for over 50 years, you don't just let a club sit in your hands; it would fly out on the downswing, if not on the backswing or the follow through.
#17
01-26-2019, 05:50 AM
 Ludovic Charter Member Join Date: Jul 2000 Location: America's Wing Posts: 29,278
Quote:
 Originally Posted by Telemark https://www.acs.psu.edu/drussell/bats/impulse.htm The inputs are just weights and speeds of the bat and ball. Essentially, the batter is only interesting in that he or she gets the bat up to speed. For a collision that lasts .7 milliseconds, the bat is essentially unanchored object.
Quote:
 Originally Posted by Chronos Speaking abstractly, the bat would be almost like an unanchored object, but the batter is still exerting some nonzero force, and imparting some nonzero work, during the brief duration of the collision, so there would be some slight advantage to the bigger batter.
I was amazed when I plugged in the equation but Chronos seems to be right, if the collision lasts .7 milliseconds and Google is right about the speed of sound in wood at > 3000 m/s. The collision lasts long enough for the force from the grip to interact with the collision site.
#18
01-26-2019, 08:26 AM
 RitterSport Guest Join Date: Mar 2002 Posts: 2,933
Quote:
 Originally Posted by Ludovic I was amazed when I plugged in the equation but Chronos seems to be right, if the collision lasts .7 milliseconds and Google is right about the speed of sound in wood at > 3000 m/s. The collision lasts long enough for the force from the grip to interact with the collision site.
Does it last long enough to travel down the bat and arms to make the weight of the body matter? (I could probably do the math, but you seem to have the equations ready to go)
#19
01-26-2019, 08:37 AM
 Ludovic Charter Member Join Date: Jul 2000 Location: America's Wing Posts: 29,278
It does have enough time to interact with the body as a whole, but I don't know if it would make the weight of the body matter, or just the strength. ETA: only barely since I'm assuming that waves travel through the human body at the same speed as through water, which is slower than wood.

Last edited by Ludovic; 01-26-2019 at 08:39 AM.
#20
01-26-2019, 12:54 PM
 RaftPeople Guest Join Date: Jan 2003 Location: 7-Eleven Posts: 6,438
Alan Nathan is a scientist that studies this stuff. Here's an article he posted about the batter's grip at impact has zero influence on the path of the ball (in summary: the wave generated by impact that travels to the knob of the bat and back to area of impact takes longer than the duration of impact):
http://baseball.physics.illinois.edu/grip.html
#21
01-26-2019, 01:09 PM
 SayTwo Guest Join Date: Oct 2005 Posts: 92
Quote:
 Originally Posted by Chronos Speaking abstractly, the bat would be almost like an unanchored object, but the batter is still exerting some nonzero force, and imparting some nonzero work, during the brief duration of the collision, so there would be some slight advantage to the bigger batter.
Not necessarily.
#22
01-26-2019, 01:31 PM
 SayTwo Guest Join Date: Oct 2005 Posts: 92
As someone who once played a level below semi-pro in men's slow-pitch softball, I think I can add some color. The mass of the bigger guy is likely to indeed play a role in determining who can get the bat up to speed faster. And yes, grip strength is very, very important -- if not critical -- in determining that. (The physics model here is a double-pendulum, with extreme forces placed on the second fulcrum point.)

Big, strong guys can 'force' and 'push' a bat through the zone, to be sure. But no big shot ever happened while the wrists were still locked down and holding on tight. A home run still? Sure. That happens all the time in the MLB. But you want to maximize things and truly let that bat fly? It's going way faster than your hands are when it hits the ball.

There's a reason people talk about it being 'effortless', or about hitting a 'sweet spot'. And there's also a reason that the big shots are pulls. It's because you see the ball coming and you have time to put all your physical things in motion and turn that energy plant as much as you can and extend those arms and hold on tight with the wrists and flail the head of the bat at that ball and hope -- hope! -- that it catches that ball square.

And when it does catch it square, it doesn't care if it came from a behemoth or a runt. It's just mass on mass, in a violent collision that will send the little guy (the ball) a long way away and slow the big guy (the bat) enough to make it not hurt the guy who swang it. My guess would be that 95+% of amatuer softball players never experience the feeling when they are fully extended and the bat is no longer a part of them and they are still touching it but it's doing what it will do. It takes a lot to have that kind of trust. But that's also what it takes to hit it over the fence. If that's what you want to do.
#23
01-26-2019, 07:39 PM
 RitterSport Guest Join Date: Mar 2002 Posts: 2,933
Quote:
 Originally Posted by RaftPeople Alan Nathan is a scientist that studies this stuff. Here's an article he posted about the batter's grip at impact has zero influence on the path of the ball (in summary: the wave generated by impact that travels to the knob of the bat and back to area of impact takes longer than the duration of impact): http://baseball.physics.illinois.edu/grip.html
So, is this the final GQ answer? Does anyone have a better cite to the contrary?
#24
01-28-2019, 03:45 PM
 Hoopy Frood Guest Join Date: Jan 2001 Location: Chicago, IL Posts: 4,513
What if the batters are standing on a treadmill?

[Sorry. I'll see myself out.]
#25
01-28-2019, 04:51 PM
 Hampshire Member Join Date: Jan 2003 Location: Minneapolis Posts: 10,857
So here's another thought experiment to toss in there.
2 motors with their axis vertical.
Each has a baseball bat attached to the motor shaft.
In A it's attached by a rigid steel bar.
In B it's simply attached by a piece of flexible cord.
Both motors are started and the bats speeds are met say around 75mph, both sweet spots equal distance from the motor shaft.
Baseball is shot at at 90mph at the sweet spot to make contact.
Which ball goes further?
#26
01-28-2019, 09:05 PM
 RitterSport Guest Join Date: Mar 2002 Posts: 2,933
From the cite that RaftPeople provided, my non-GQ guess is that it won't matter since it takes longer for the impact wave to get to the base of the bat and back to the ball than the ball is touching the bat. So, (to speak non-scientifically) by the time the bat "realizes" it's attached to a steel bar instead of a flexible cord, the ball is already gone.
#27
01-29-2019, 12:05 PM
 SayTwo Guest Join Date: Oct 2005 Posts: 92
Quote:
 Originally Posted by Hampshire So here's another thought experiment to toss in there. 2 motors with their axis vertical. Each has a baseball bat attached to the motor shaft. In A it's attached by a rigid steel bar. In B it's simply attached by a piece of flexible cord. Both motors are started and the bats speeds are met say around 75mph, both sweet spots equal distance from the motor shaft. Baseball is shot at at 90mph at the sweet spot to make contact. Which ball goes further?
It might be the same, but I don't think that's the instructive takeaway, if we are talking about any matters at all of real-life practicality. What will happen in the case presented in the OP is that the smaller/weaker guy won't really be able to get that bat up to the same speed as the other guy -- or in other words, his motor with vertical axis just won't turn as fast.

If we want to just talk about abstractions, then that's surely fine. But in the real-life scenarios, grip strength and mass and such matter.
#28
01-29-2019, 03:01 PM
 RitterSport Guest Join Date: Mar 2002 Posts: 2,933
Quote:
 Originally Posted by SayTwo It might be the same, but I don't think that's the instructive takeaway, if we are talking about any matters at all of real-life practicality. What will happen in the case presented in the OP is that the smaller/weaker guy won't really be able to get that bat up to the same speed as the other guy -- or in other words, his motor with vertical axis just won't turn as fast. If we want to just talk about abstractions, then that's surely fine. But in the real-life scenarios, grip strength and mass and such matter.
I weigh about 180 pounds. I guarantee that a, say, 130 pound professional baseball player will be able to get the bat swinging faster than I can. The question is, if the bat is swinging at a certain speed, will it go further with the heavier batter. I think that's answered, and I'm not sure what your post added to that. Are you saying that it's impossible that a 100 pound guy will get a bat up the same speed as a 200 pound guy? Extra weight doesn't mean extra strength. Plus, the 200 pound guy could just put less effort into the swing -- we just need the bat speed to be the same.

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