Fastball Speeds

[MFS62]

I've noticed that when the "stuff" of a pitcher is written about in scouting reports, the speed of the two-seam and four seam fastballs are different by as much as 3-4 mph. That seems strange.
Both pitches are thrown with the same arm speed/ angular momentum and the mass of the baseball is a constant. The only thing different is the grip. So why the difference in speeds?
Is it because the different grips "present" different seams to the air, producing variances in resistance?

Are there any engineers or physicists out there who can shed some scientific light on this?
or
Does anyone have Jay Hook's contact information?

Later

[duan]

well a 2 seam fastball is a different pitch.
It's what's often called a sinker; it's gripped differently & movers more. Hence the difference in speed.

[MFS62]

duan wrote: well a 2 seam fastball is a different pitch. It's what's often called a sinker; it's gripped differently & movers more. Hence the difference in speed.

Not according to this.

http://www.popularmechanics.com/outdoors/sports/1283281.html?page=3

It explains the difference in movement, but not the difference in speeds other than maybe the fact that one is held farther back in the hand. That slight difference could change the angular momentum.

Later

[Guest Rockin' Doc]

This site has more information on pitching grips than most of us ever cared to know. It does briefly address the difference in speed and movement between 2-seam and 4-seam fastballs.

[MFS62]

Thanks , Doc.
I guess when you go for the movement (2 seamer), it sacrifices a few MPH of speed.

Later

[Guest holychicken]

MFS62 wrote: Thanks , Doc. I guess when you go for the movement (2 seamer), it sacrifices a few MPH of speed. Later

Think of it from a physics standpoint.

If you throw a pitch with a certain arm angle and speed you will always apply the same force, roughly.

If you throw one pitch with no spin, all the force is going to go into the speed. If you throw another one with spin, part of the force has to go into making the ball spin, which would mean less force for speed.

[Guest Rockin' Doc]

You essentially throw the 2-seam and 4-seam fastball the same way. The difference in movement come from the amount of "lift" the natural backward rotation gives each pitch. The 4-seam fastball receives greater resistance due to the effect of the seams and therefore it sinks less than a 2-seam fastball does.

Super slow motion photography of the proverbial high, hard one (4-seam fastball) has shown that it does not really "sail" or rise. It simply holds it's initial trajectory better (or sinks less) than a 2-seam fastball and therefore gives the illusion to the hitter that it rose.

I truthfully can't understand any potential difference in velocity between the two. Until recently, I don't remember a distinction being made between the two regarding their respective velocities. Generally, power pitchers tend challenge hitters up in the strike zone and tend to throw the 4-seam fastball. Pitcher's that lacked overpowering velocity generally need to keep the ball down in the strike zone to be successful, so they tend to opt for the "sinker" (2-seam fastball).

[Frayed Knot]

Truer flight = less 'turbulence' = greater speed