Physics of Baseball | home
How Do Pitchers Throw Different Types of Pitches?
The game of baseball is played out as duel between the pitcher and the
batter. The pitcher will try to throw a ball so that the batter doesn't hit it.
How does the pitcher accomplish this?
The pitcher has to throw the ball inside a target of 20”x23”x17” box such
that even if the hitter hits the ball, he won't be able get a clear hit. To
achieve that goal, the pitcher uses various pitches, such as the curve ball,
sinker, slider, or fast ball.
As the pitcher releases the ball, the grip will put a spin on the ball. What
happens to the ball depends on what spin was put on it. What causes the
ball to curve, slide or stay in a strait pattern? This all has to do with the fact
that there is drag force, or air resistance. A curve ball is created when a ball
The faster flowing air under the ball creates less pressure,
which forces the ball to dive or break. Baseball would be a dull game without
drag force because there would be no curves, sliders, or knuckle balls.
So what does this force do to the ball? What happens to the ball once it
is released is actually called the Magnus effect. For a spinning ball, the
stitches on the ball will cause pressure on one side to be less than on its
opposite side. This will force the ball to move faster on one side than the
other and will force the ball to “curve.” This is the Magnus Effect.
Origin of the Magnus force for a ball of radius , moving with speed , and
spinning with angular velocity about an axis perpendicular to its direction
The conventional classification of baseball pitches is in terms of the
direction of the ball's axis of spin.
A “slider” is thrown such that its axis of rotation points vertically upward,
which is the direction of spin generated by the natural clockwise rotation of
a right-handed pitcher's wrist. The Magnus force causes the ball to curve
sideways, away from a right-handed hitter.
The “curveball” is thrown such that its axis of rotation, as seen by the
hitter, points upwards, but also tilts to the right. The Magnus force acting
on a curveball causes the ball to deviate both sideways and downwards.
Thus, although a curveball usually doesn't move laterally as far as a slider,
it dips very rapidly--which makes it difficult to hit.
A pitch that curves towards a hitter is harder to hit than one that curves
away. It is actually possible for a right-handed pitcher to throw an inward
curving pitch to a right-handed hitter. Such a pitch is known as a “screwball.
” The ball is thrown such that its axis of rotation, as seen by the hitter,
points upwards and tilts to the left. The pitch dips rapidly, like a curveball,
but has a sideways displacement in the opposite direction to normal.
Probably the most effective pitch in baseball is the “fastball.” The Magnus
force acting on a fastball has a large upward component, slowing the ball's
rate of fall. The ball is thrown such that its axis of rotation, as seen by the
hitter, points downwards and tilts to the left.
How much will a baseball curve?.
The equation is as follows :
FMagnus Force = KwVCv
FMagnus Force is the Magnus Force
K is the Magnus Coefficient
w is the spin frequency measured in rpm
V is the velocity of the ball in mph
Cv is the drag coefficient