THE CURVING OF A BASEBALL 



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in end view of Fig. 9). This is equivalent to the ball going through the 

 air with a rotary motion and the difference in pressure on the two sides 

 curves it as shown by the heavy arrow. 



If the rotation of the ball is reversed, the lower-pressure region 

 (higher velocity region) is on the other side of the ball. This is equiv- 

 alent to the ball going through the air with a rotary motion as shown in 

 Fig. 10 and the difference in pressure on the two sides of it causes it to 

 curve as shown by the heavy arrow. 



