**Effect of Changing Baseball Parameters**

**Alan Nathan, March 29, 2021**

The table below shows
the effect of changing various baseball parameters on exit velocity (EV) and
fly ball distance. These
numbers were taken from the May 2018 report of the MLB Home Run Committee,
Appendices A and B (slightly updated, see link below). Note that increasing the weight by 0.125 oz decreases
the EV (resulting in a __decrease__ in distance by 4.6 ft) and decreases the
drag acceleration (resulting in an __increase__ in distance by 3.5 ft), so
that the net change in distance is a decrease of 1.1 ft. Increasing the circumferences does not affect
the EV but increases the drag, thereby reducing the distance. All the effects shown in the table are both
linear and uncoupled in their effect on distance for small changes in the
parameter. Therefore to see the effect
of any small change, simply scale appropriately, make sure the sign is correct
(i.e., change the sign if the parameter has decreased), and add.

Note that the “CCOR” is the “Cylindrical Coefficient
of Restitution” and is a measure of the “bounciness” of the ball. A higher CCOR means the ball leaves the bat
with a higher speed, all other things equal.
It is a quantity that can be measured in the laboratory. Rawlings does their own measurements on
samples of ball lots on a regular basis.
In addition, MLB employs an independent research laboratory to do
measurements of CCOR as well as other features of the baseball.

Consider
the following made-up example (i.e., these numbers have nothing to do with any
actual change in the ball): Suppose the weight
is smaller by 0.1 oz, the circumference is smaller by 0.05 in, and the CCOR is
smaller by 0.01. The net effect on
distance will by:

1.1*(0.1/0.125) + 3.7*(0.05/0.125) -4.9*(0.01/0.008)
ft, or -3.8 ft.

Baseball
Parameter |
MLB
specification |
change |
Change
in EV (mph) |
Change
in Distance (ft) |

weight |
5.125 ± 0.125 oz |
+0.125 oz |
-0.94 |
-4.6 + 3.5 =
-1.1 |

circumference |
9.125 ± 0.125 in |
+0.125 in |
--- |
-3.7 |

CCOR |
0.4825 ± 0.0225 |
+0.008 |
+1.00 |
+4.9 |

Reference: Report of the Home Run Committee, May 2018.

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