Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Astronomer_FB on 15/03/2009 04:47:01

Title: Bunting the Baseball
Post by: Astronomer_FB on 15/03/2009 04:47:01
My coach is not sure about why when you go for a bunt and you put the front of the bat below the back and you do hit the ball it gets popped up high. What is the physics behind it and why does it happen?
Title: Bunting the Baseball
Post by: Chemistry4me on 15/03/2009 04:58:11
I don't get your explanation. [???][???]

Especially:

you put the front of the bat below the back
Title: Bunting the Baseball
Post by: Astronomer_FB on 15/03/2009 08:33:01
when i say "front" i am talking about the area of the sweet spot or the part where you hit the ball and the back is where your hands are. so when you bunt it wrong the part where your hands are supposed to be is above the front of the bat and if the ball hits the bat like that it bounces high why?
Title: Bunting the Baseball
Post by: lyner on 15/03/2009 10:25:45
With a relatively simple tool like a baseball bat, the sweet spot will be the point where an impact with the ball will not tend to rotate it. That will be near  (but not at - because the presence of you hand will make a difference) the centre of mass.
If the ball impacts beyond this point, the bat will tend to rotate backwards (a 'slice') and, if it impacts nearer the hand it will tend to rotate forwards (a 'hook').
I only used a baseball bat once and I know nothing about the techniques but that principle should apply.
If the bat is at all springy (flexible) then things could change a bit.
I remember reading a New Scientist article several years ago about baseball bat design and the ideal weight. Apparently it depends a lot upon the batter's strength and the mass of his arms.
'Strung' raquets have a sweet spot almpost in the middle, where the strings all end up with a similar tension - this also ensures the ball goes in the right direction. It's more complicated, I think.

btw This problem is very similar to the problem of where is the best place to put a doorstop to reduce the stress on the hinges when the door is thrown open.
Title: Bunting the Baseball
Post by: swansont on 16/03/2009 16:58:58
If you hit the ball below its center of mass it will tend to pop up.  If you hit it above the center of mass, it will deflect down.

I think it would be clearer if the discussion used proper terminology — the fat part of the bat is the barrel, and the skinny part of the bat, with the knob, is the handle.  If you hold it so the barrel is below the handle, I think you will have a tendency to hit the ball below its center of mass.
Title: Bunting the Baseball
Post by: lyner on 16/03/2009 22:07:46
Ah. So we're talking in the other dimension. I guess I was thinking golf, cricket etc etc.

On a simple level, you can say that, for two objects with circular cross sections, the direction of the force which acts on both objects will be along the 'line of centres'. That should tell you where the ball will go. Games like pool and snooker let you calculate accurately where the coloured ball will go. "bat' games are harder to analyse but the same principle applies.