# lec18 - L ECTURE 18 S AILING Sailing Wave drag Surface...

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L ECTURE 18: S AILING + Sailing Sliding/Rolling (revisited) More trajectories

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In a corner kick, the perpendicular force is horizontal Hay. What do we call the force that curves the ball to the right in the video? Which force is much larger in soccer: gravity or ﬂuid forces?
Discus Video What form is most of the energy in before the athlete throws the discus? After he releases it? Why does the athlete spin slower when he releases the discus? Why does he put spin on the discus? 1. What are the principal forces acting on the discus while in ﬂight? (How does each affect the optimal launch angle?) (a) Gravity (b) Air drag (c) Air lift (d) All of these (e) Two of these

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Long Jump Video Why does he take off at an angle < 45 o ? Why does he keep moving his legs once he is in the air? Discuss the different forms of energy in this jump. Notice the position of his feet when he lands. By doing this he shifts the position of his feet relative to his _____________.
Why can a sailboat go faster upwind? 1) You tried to trick us! It is not possible to travel faster upwind because you’re always fighting the breeze and in a downwind you have the wind pushing the boat right behind you which propels it much faster. 2) In Sailing, it is possible to travel faster upwind that downwind because the going upwind creates a net force propelling the boat in a forward direction, while in downwind there is no net force therefore the boat is not being pushed forward by a force. 3) When running downwind the faster the boat goes the less force is exerted on the sail and a balance is reached when the boat cannot go any faster. 4) Sailing into the wind creates a stronger force on the sail as the boat picks up speed. When running downwind the faster the boat goes the less force is exerted on the sail. 5) It is a parallelogram of forces. Sailing into the wind creates a stronger force on

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## This note was uploaded on 12/12/2011 for the course PHYS 17 taught by Professor Mcwilliams,r during the Fall '08 term at UC Irvine.

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lec18 - L ECTURE 18 S AILING Sailing Wave drag Surface...

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