What are three ways a sail can produce force?

Question

Use any priciples of physics to answer

Answer 1

1. Like an umbrella, the air pressure behind the sail is captured by the sail and propels the boat forward.

2) Like an airplane wing, the sail is shaped like a foil so that there is a pressure differential due to air flow across the surfaces. The lower pressure on the leading side of the sail pulls the boat forward.

3) Sideways, which is couteracted by the keel or centerboard.

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Answer 2

Only three?

With the wind behind, it is 'pushed along' - air resistance.

With the wind at an angle there is a pressure difference - Bernouilli.

With the sail in the water there's water resistance - viscosity.

With the sail on top of you there's weight - gravity.

With the sail fully stretched there's an elastic force - Hooke's law.

Then radiation pressure in strong sunlight. The sail can move the boom and knock you out. The rope can become wound round your leg and tip you overboard. Rain can settle in the sail and add to the weight. If it is electrically charged there will be electrostatic forces. Birds can settle on it.

Just use your IMAGINATION!