Can the spin of a baseball reverse direction

when the ball bounces?     Bounce 1      Bounce 2







Closeup of the finger action, in slow motion,

when pitching a fastball and a slider.


The ball spins in the direction that the fingers

pull on the ball (as expected).




How to pitch a ball with a sideways break of six feet or more.

Step 1: Polish one side of ball

Step 2. Roughen other side or glue a loop of string around that side

Step 3: Reduce ball mass to about 15 or 20 gram.

Step 4: Hold ball with smooth side on your right.

Step 5: Throw a fastball straight at camera (with backspin).



My pitching effort is of no practical value (like a lot of physics) but at least it

demonstrates  the physics behind the swing of a cricket ball with its rough

and smooth sides and seam. How about a baseball?  Does it have a rough

and a smooth side or doesn't it? What if it is spinning? That might be of

practical interest, at least for knuckleballs.



Here is a 100 mm diameter polystyrene ball with a baseball seam

glued to the ball. It breaks 90 cm over a distance of 5 m if the seam

is aligned properly, otherwise there is no break or a smaller break.


90 cm break            70 cm break         no break      (all 300 fps)








The center of percussion (COP) of a hand held bat is not the same

as the COP of a freely suspended bat. This movie shows that the axis

of rotation of a hand held bat is near the wrists (regardless of the impact

point on the bat). The COP is NOT the sweet spot of a bat.




Low speed baseball bounce, filmed at 1000 frames/s




Why are baseballs and softballs so hard? Softer balls would reduce injuries,

help prevent bats breaking and reduce the trampoline effect. The Kenko ball

here (a hollow, rubber ball) is 10 times softer than an adult baseball and 3 times

stiffer than a tennis ball. It is used in youth leagues in Japan, Australia etc.



Click for more info


How fast can you spin a 12 inch softball?    

1000 rpm?  (12 in is the circumference!)




Cricket ball colliding with a baseball to see which is heavier.


          Movie1      Movie2




Swing speed vs bat weight. Light bats can be swung faster. By how much?


               232 g bat           871 g bat        1333 g bat





Hoop modes of a hollow bat (the ping sound).


      Bat mode         Cylinder 1 (900 Hz)     Cylinder 2  (200 Hz)






Measuring outgoing ball speed at different  impact points on a bat



Impact at 2 cm      Impact at 7 cm      Impact at 12 cm

Impact at 17 cm    Impact at 24 cm    Impact at 31 cm  

Strike at 2cm         Strike at 7 cm        Strike at 12 cm       

Strike at 17 cm      Strike at 24 cm      Strike at 31 cm