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The right image shows what happens when the skydiver has tucked into a ball, thus decreasing the body area. The decreased area means that there is a lower air force because the air is coming into contact with less of the body’s surface. However, the gravitational force remains the same, so the net force is pushing down. This means the skydiver will increase downward momentum. The skydiver will continue downward motion until he or she stretches out again to increase the air resistance force to once again be equal to or greater than the force of gravity. A skydiver can reach a speed of 120 miles per hour in the spread-eagle position (shown on the left side of figure 1) but, when tucked in, might reach up to 200 miles per hour in speed.

F air

Figure 1

F air

F gravity

F gravity

Twists and Turns How would a skydiver make sideways moves? Skydivers learn to position their bodies just so to move left and right. The blue ball toward the bottom of Figure 2 represents air hitting the body at an angle. This causes the skydiver

In the spread eagle position, skydivers will fall as fast as 120 mph.

CHAPTER 1 : SKYDIVING

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