On the beach in summer, with blue skies and clear water, a rumbling sound suddenly comes from behind. A long rope is being dragged behind a speeding speedboat, and at the end of the rope, a person with a bronze-colored skin is pulling on the handle. We can see him either sliding at high speed, flipping to the left and right, or spinning and jumping. This is the wonderful water sport — water skiing.
When you see water skiers gliding quickly on the water, have you ever wondered why they don't sink when standing on the board? The secret lies in the small board under their feet.
When water skiers are skiing, their bodies always lean backward, and they use their feet to push the board forward, creating an angle between the board and the water surface. When the speedboat in front of them pulls the skier forward with a rope, the skier applies a downward force on the water surface through the board. Moreover, the greater the traction of the speedboat on the skier, the greater the force the skier applies to the water surface. According to Newton's Third Law (the law of action and reaction), the water surface will in turn apply an upward reaction force on the skier through the board. When the board tilts to a certain extent on the water surface, so that the component of this reaction force in the vertical direction is equal to the skier's weight, the skier will not sink. Therefore, as long as water skiers rely on their skills and control the tilt angle of the board under their feet, they can glide quickly on the water surface.