The Science of a Baseball
By: Paige Wedan
Hour: 4


Question: How does a baseball curve?

People never really know if a baseball actually curves or not when someone is pitching it. People thought it was just an optical illusion and then when they got the use of cameras, they knew it was true. But there's still some questions as to ​HOW a baseball curves.

When you reach out of the window in a moving car, you can feel the wind PUSHING on your hand and the force of the wind makes it harder for you to move your hand AGAINST the wind. On an airplane, the wind rushing through the top wings will move faster than the bottom, which pushes the wing and airplane upward. Those are examples of BERNOULLI'S PRINCIPLE.

Magnus force is similar to Bernoulli's Principle but not quite, otherwise the effect of a curved ball woul be called, Bernoulli's Principle. For a spinning ball, the stitches on the ball will cause PRESSURE on one side be less on the other side. This forces the ball to "curve". This is the Magnus Effect.



SPEED
images.jpg
This picture shows the baseball when it's being thrown to the batter.
It shows the SPEED of how fast the ball is going to go to affect a curve ball.
You have to have certain speed in order to get a curve ball.
So speed is the most important part of throwing a curve ball.

  • Velocity is the rate the position changes over time. Velocity is referred to as speed, and many people think that velocity and speed are the same, but they're not. Velocity is a vector while speed is the scalar of the vector. A vector can be thought of as an arrow with a specific direction and length. Scalar is the length portion of the vector. For example, a velocity could be 70 miles per hour to the north, while its corresponding speed would be 70 miles per hour. So the velocity of a curve ball would be going the same miles per hour north.

  • Acceleration is the rate the velocity changes over time. So the acceleration of a curving baseball would be going faster when the pitcher throws it then it would start to decrese the speed as it gets closer to the batter.

Friction


You can't really explain the curving of a baseball with friction because faster things have more friciton so trying to explain it wouldn't make sense. In curve balls, the ball curves to the slower side.
The spin of the ball is allowing air to move more quickly on the side that's spinning with the wind, and slower on the side that's spinning against the wind. The faster the air, it generates less pressure on the baseball which is another example of the Magnus Effect.

How much will a baseball curve?

The equation is, FMagnus Force = KwVCv
where:

  • 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

Bibliography:

http://www.exo.net/~pauld/popularerrors/curveball.html
http://www.bu.edu/gk12/kai/Lesson%206/BP_Back.pdf
http://172.16.10.113:15871/cgi-bin/blockpage.cgi?ws-session=184658771


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