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Honors for Thorough Reasoning

Flying Across the Water

The captivating aspect of the photo is the sail is parallel to the direction of motion! The type of sailing in the image is close-hauled because ropes allow the mainsail to swing left, hauled in close, the mainsail is right over the hull. From the wake showing its direction and the sails, I infer the wind is coming from the left, hitting the sail at about 45 degrees. The boat appears to be traveling in a straight line, meaning all translational forces and rotational forces must be balanced. The wind on the sail produces a lift force perpendicular to the wind, which points towards the bottom of the photo. The drag force is in the direction of the wind, which is to the right of the photo. The lift force can be broken down into components relative to the boat; a small component of the lift points to the front of the boat, while the larger component of the lift is parallel to the boat's hull and tends to push the sail towards the water. Still, the boat's keel extends down into the water and resists the rotation tendency. Drag forces between the boat and the water balance the forward force from the sail so that the boat's speed remains constant. Just as I was flying over the water in an airplane when I took this photo, the boat was also flying over the water using the lift force on its sails.