TURF

BJ Upton

 The ball doesn't pick up speed when it bounces. Even if it's "hit just right." #physics

If you don't think that ball picks up speed scooting across that plastic thru the box versus the change in spin imparted by fescue... you must be watching from the cheap seats. Sit right behind the plate and watch.

The rules of physics apply to baseball. An object does not gain speed unless a force is applied to it that accelerates the object. The only force applied to a ball after it leaves the bat is friction, which slows it down. It might slow down less on turf than grass, which is what you are likely noticing. 

Yes true. That is a more accurate statement. The traditional fescue imparts a friction that can be more inverse depending on the trajectory and spin of the batted ball... thus balls cam and do come thru the box quicker at times.  And it's scary. Not sure if powhatan pitcher had his bare hand broken, but reached out instinctively on one of these... and clover hill was hitting what looked like golf balls back at the deep run reliever. So yes, it would be more of less friction and the skimming action of these type rips.

Whether in the cheap seats or box seats, the ball does not speed up on any type of surface. Now…if you want to talk about rising fast balls...

Most fields are Bermuda as well.  Shorter grass more heat tolerant.

Global warming. It's amazing how many fields in Virginia were tall fescue not too long ago at all; but needs to be kept at 2" or so - so definitely slow... and of course still a lot of bluegrass/rye in cooler zones. Artificial is optimum just because less days lost. I am thinking UVA is wondering if they should go there?

 

Can a batter impart enough spin (topspin) that the forward velocity increases when it bounces?  Talking about the "moment" before the ball bounces and the "moment" after it bounces (milliseconds type measurement).  You can witness this on some choppers (ball takes a forward hop as the spin kicks in) but not sure what spin would be required in the initial velocity were 80mph+ - possible I guess but would take very high RPM.  The argument would be that the turf provides more of a bite for the spin to kick in versus grass which might deaden this effect.

 

Anyone hear Alan Nathan on NPR the other day?  He was interviewed about the increased college home runs and the new low seam ball.  He is a professor at Univ of Illinios and I believe some folks on this board have coversed with him - someone was had asked him about hitting down on the ball to provide lift - Alan was supposed to get back with him to help settle the discussion.

       
       
Yes that was me.  He agreed there is no way to hit down on the ball and 'hit the top half' and somehow magically create backspin and lift.  However we discussed via e mail the difference between top half of the ball according to a horizontal line parallel to the ground and top half of the ball in accordance to the ball/swing plane.  The average fastball comes in at a 9 degree downward angle.  So if your attack angle was 9 degrees uppercut the the ball and the bat would be on the same plane.  Now the question is if you hit ever so slightly above center ACCORDING TO THAT PLANE could you achieve enough lift on the ball to get over the infielder's head and drop in front of the outfielder.  He believes it could and I guess the eye test tells us that as well cause you do occasionally see those top spin hump back line drives.  But the notion that you could hit top of center according to parallel with the ground and achieve lift is simply silly.  He said he was in process of doing some work on this and will release his study soon.  Stay tuned!  Unfortunately I have not gotten a reply from my last e mail asking for a couple clarifications.

My son played on perhaps the most ridiculous full-turf field I've ever seen this weekend at Adams State University in Alamosa, CO. It was like a trampoline. I'd say half the hits I saw this weekend were balls that bounced over the infielders' heads. I also saw a LOT of fly ball singles hit the turf, bounce over the outfielder's head and turn into triples. We also had seven ground rule doubles in one game - balls that hit a good 30-40 feet shy of the fence and bounded over.

might be fun to do back flips on though

A ball cannot gain velocity.  However, a ball that takes a high hop, then a low/skip hop, will fool the fielder into thinking that it did.  The airborne time of the high hop followed by the low angle of the skip hop catches the fielder by surprise and often with his glove and body positioned too high to react in time.

 

I don't know if anyone has measured whether this occurs more often on turf fields vs. natural surfaces.

 

I do know that modern AstroTurf of the type used at UR (and previously at JMU, VT, Radford, Wake Forest, etc.) has been developed to try to provide the slowing friction more akin to natural surfaces and less like the AstroTurf that got such a bad rep back in the 1970's and 1980's.  Those ground-up rubber bits that look like rabbit droppings are a big key to this.

2020dad - thanks for the update - keep em coming.  I think the interaction between the physics of baseball will be greatly expanded with the new tracking technologies being put into place.  Most folks seem to think a pitcher's spin rate will be the most interesting to follow during the next couple of years.

Also, I am not a physicist nor do I have any scientific training, but I will say a ball can gain forward velocity be converting spin energy into directional energy (no idea if this is correct terminology).  Not talking about creating energy, just transferring energy.  It does occur on mishits where tremendous spin can be created (spin in the opposite direction can also be transfereed in such a way as to slow down the ball - think of a golf chip shot).  It probably is of zero consequence on hard hit balls (less spin and high initial velocity to begin with) in the infield, but not sure anyone can say a ball cannot gain (forward) velocity without exception.

I think you can either come under or over a pitched ball and with the rubber granular sub base and synthetic blades you could possibly accelerate the ball?  If I throw a super ball against a wall... might it come back at me quicker?