(a) Calculate the approximate force on a square meter of sail, given the horizontal velocity of the wind is 6.00 m/s parallel to its front surface and 3.50 m/s along its back surface. Take the density of air to be 1.29 kg/m 3 . (The calculation, based on Bernoulli's principle, is approximate due to the effects of turbulence.) (b) Discuss whether this force is great enough to be effective for propelling a sailboat.
(a) Calculate the approximate force on a square meter of sail, given the horizontal velocity of the wind is 6.00 m/s parallel to its front surface and 3.50 m/s along its back surface. Take the density of air to be 1.29 kg/m 3 . (The calculation, based on Bernoulli's principle, is approximate due to the effects of turbulence.) (b) Discuss whether this force is great enough to be effective for propelling a sailboat.
(a) Calculate the approximate force on a square meter of sail, given the horizontal velocity of the wind is 6.00 m/s parallel to its front surface and 3.50 m/s along its back surface. Take the density of air to be 1.29 kg/m3. (The calculation, based on Bernoulli's principle, is approximate due to the effects of turbulence.) (b) Discuss whether this force is great enough to be effective for propelling a sailboat.
A frequently quoted rule of thumb in aircraft design is that wings should produce about 1000 N of lift per square meter of wing. (The fact that a wing has a top and bottom surface does not double its area.)
(a) At takeoff the aircraft travels at 65.0 m/s, so that the air speed relative to the bottom of the wing is 65.0 m/s. Given the sea level density of air to be 1.29 kg/m³, how fast (in m/s) must it move over the upper surface to create the ideal lift?
m/s
(b) How fast (in m/s) must air move over the upper surface at a cruising speed of 245 m/s and at an altitude where air density is one-fourth that at sea level? (Note that this is not all of the aircraft's lift--some comes from the body of the plane, some from engine
thrust, and so on. Furthermore, Bernoulli's principle gives an approximate answer because flow over the wing creates turbulence.)
m/s
t
(a) Calculate the retarding force due to the viscosity of the air layer between a cart and a level air track given the following information—air temperature is 20o C, the cart is moving at 0.400 m/s, its surface area is 2.50 X 10-2 m2, and the thickness of the air layer is 6.00 X 10-5 m. (b) What is the ratio of this force to the weight of the 0.300-kg cart?
(a) Calculate the absolute pressure at the bottom of a freshwater lake at a point whose depth is 27.5 m. Assume the density of the water is 1.003X10 kg/m³ and that the air above is at a pressure of 101.3 kPa. (b) What force is exerted by the water on the window of a submarine at this depth if the window is circular and has a diameter of 35 cm?
Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)
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