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Drag Force

# Drag Force - called terminal velocity v t When the object...

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Drag Force The friction force we have discussed so far acts when two surfaces touch. The force that tends to reduce the velocity of objects moving through air is very similar to the friction force; this force is called the drag force. The drag force D acting on an object moving through air is given by where A is the effective cross-sectional area of the body, [rho] is the density of air and v is the speed of the object. C is a dimensionless drag coefficient that depends on the shape of the object and whose value generally lies in the range between 0.5 and 1.0. The direction of the drag force is opposite to the direction of the velocity. Figure 6.11. Drag Force. Because of the drag force, a falling body will eventually fall with a constant velocity, the so
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Unformatted text preview: called terminal velocity v t . When the object is moving with its terminal velocity v t the net force on it must be zero (no change in velocity means no acceleration). This occurs when D = mg, and the terminal velocity v t has to satisfy the following relation: and v t is calculated to be The equation for v t shows that the terminal velocity of an object increases with a decreasing effective area. The terminal velocity of an object is the final velocity it obtains during free fall. The object will obtain this velocity independent of whether its initial velocity is larger or smaller than the terminal velocity (see Figure 6.11)....
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