- #1

shizzznit

Much thanks

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- Thread starter shizzznit
- Start date

- #1

shizzznit

Much thanks

- #2

jamesrc

Science Advisor

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[itex] F_D = \frac{C_D\rho A v^2}{2} [/itex]

where F

- #3

ahrkron

Staff Emeritus

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Air resistance is usually taken into account via a differential equation; in simple situations, it grows linearly with the speed of the object.

- #4

shizzznit

Thanks very much Jamesrc

having some trouble figuring out the velocity (after the bat) but thanks for the help!

- #5

enigma

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You need to multiply the force times a small step size and add it to the velocity and repeat. Works best on a computer.

- #6

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- #7

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http://en.wikipedia.org/wiki/Drag_coefficient

The drag force depends on whether the air flow around the object is linear or turbulent, which then determines whether the drag force is proportional to the velocity, or the velocity squared. Also, the drag depends not only on the object size (frontal area) and shape but also on the surface roughness.

Bob S

- #8

rcgldr

Homework Helper

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It turns out that in the real world it's more complicated, but instead of modifying the equation to one more realistic, CRoughly:

[itex] F_D = \frac{C_D\rho A v^2}{2} [/itex]

- #9

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Jamesrc suggests taking an average value of Cd, in reality you cannot do this. As Cd depends heavily on Reynolds number. Above a critical number for a ball (and it depends on the ball) the Cd will be a steady 0.2sh. Below the critical Re number the Cd will raise until it nears the critical Re number and will then drop sharply.

I did not mention it beucase if this is a generic textbook case for a baseball, his assumption of taking a middle Cd value is probably valid.

- #10

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how can i measure friction in this case

and how can a measure air resistence

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