What makes sailboats go

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Posted on 11 Nov. All Rights Reserved. This is called apparent wind. Sailboats utilize both true wind and apparent wind.

One force pushes the sailboat, and the other force pulls, or drags it forward. True wind always pushes a boat. If a boat sails absolutely perpendicular to true wind, so the sail is flat to the wind and being pushed from behind, then the boat can only go as fast as the wind—no faster.

But when the boat travels at an angle to the true wind, the apparent wind suddenly generates a powerful force. That dragging is done with this force called lift. In fact, the physics that allow an airplane to fly are the same physics that allow a sailboat to travel faster than the wind.

Put your arm straight out the window, palm down to the ground like an airplane wing. Now tilt the palm of your hand very slightly up; your arm will rise with the force of lift. More about hull shapes, bouyancy and sails. Australian Marine Services Directory has links to weather services, marine services and other information. Coriolis forces and the reasons behind the major ocean currents and winds.

Another puzzle involving relative motion of the air: the plane on the conveyor belt. Did you know that both the special and general theories of relativity are important in the Global Positioning System? See this link from Univ. See where the satellites are at the moment in this animation from J-Track. Details at Science Outreach Centre news and Activities for students and teachers. Answer to puzzle. The faster heat is the one with no wind.

When the wind and the water both move W to E at 10 kt, the boats drift down the river at 10 kt, with their sails hanging limp. In the heat with no wind as measured on the land , a drifting boat has a headwind of 10 kt. You can tack into that.

Of course, you don't get something for nothing. In the heat with wind, the river does very little work on the boat. In the heat without wind, it exerts much greater force on the boat, in particular on the keel or centreboard.

Much of that work goes into disturbing the air downwind of the boat's sails. The man in the photo at right did a lot of sailing on rivers: he would have known that. Modified 10 Jan 03 J. Wolfe unsw. Joe's scientific home page Joe's educational pages Joe's music page. An experiment. Here is what my left hand looks like as I bicycle, signalling a left turn.

If my hand is flat and horizontal, I just feel the drag force of the wind acting backwards. But if I tilt my hand up a little at the front, I feel lift force as well: the force on my hand is both upwards and backwards. The arrows show the wind speed relative to me. To get past my hand, the wind is deflected down, and this pushes my hand up as well as back.

Sailing close to the wind uses the shape of the sails to generate lift. To flow around the sails, the wind has to deviate in direction, as shown by the arrows for initial velocity v i and final velocity v f , which are given with respect to the boat.