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WHY?
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The fastest swimmers generate thrust by moving their
arms and hands like a propeller to generate a lift type force. To
visualize lift as a propulsive force, think of an airfoil flying from
right to left. Notice that the lift is acting up in the positive
vertical direction. Now, rotate the airfoil 90 degrees so that it is
moving from the top of the page to the bottom. Notice that the lift
force is now directed to the left which is the direction that the swimmer
is moving. So, even though the swimmer is moving from right to left, his
hand is moving from top to bottom and the lift force contributes to the
thrust.
Therefore, the swimmers arm stroke becomes similar to
an airplane's propeller. It should also be noted that the hand must
continue to move in the directions perpendicular to the direction of
forward movement in order for this lift force to be produced.
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ASSESSMENT: Can the student communicate
what they observed?
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