When an airplane takes off it sheds a starting vortex. We have been using a horseshoe vortex model for the finite wing, but a square closed loop might be more realistic. Estimate the downwash velocity induced at the center of the wing by the starting vortex for a small plane (mass 1000 kg, wingspan 11 m, speed at takeoff 25m/s) for a distance from the starting vortex to the wing of 10 m, 100 m, and 1000 m. Comment on the magnitude of the effect. Assume standard atmospheric conditions and neglect the ground effect.

69. air frictionthe velocity of the satellitea. decreases b. increases c. sometimes increases sometimedecreases d. no effect at all70. the unit of gravitational potential energy isa.jouté b.watt c. newtond.pascal71. which of the following is not influenced by a magneta. cobalt b.copper c.irond. nickel72. one joule of work done in one second by unit positive chargea.1 watt b.1 volt c.1 js d. none73. the most deviated colour of light after passing through a prisea. violet b.red c. green d.yellow4. a coin is placed below a beaker fill with water upto 12 cm isdisplaced by water isa. 9cm b.6cmс.3cmd.7cm