# Air Speed and Wing LiftA frequently quoted rule of thumb in aircraft design is that wings should produce about 1000 N of lift per square meter of…

1. Air Speed and Wing Lift 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.) At takeoff, an aircraft travels at 60.0 m/s, so that the air speed relative to the bottom of the wing is 60.0 m/s. Given the sea level density of air to be 1.29 kg/m3, how fast must it move over the upper surface to create the ideal lift?   How fast must air move over the upper surface at a cruising speed of 240 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.) 2. Power output of the heart’s left ventricle The left ventricle of a resting adult’s heart pumps blood at a flow rate of 83.0 cm3/s, increasing its pressure by 117 mm Hg, its speed from zero to 31.0 cm/s, and its height by 5.00 cm. (All numbers are averaged over the entire heartbeat.) Calculate the total power output of the left ventricle. Note that most of the power is used to increase blood pressure.3. Air viscosity in air track experiments 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 20°C, the cart is moving at 0.360 m/s, its surface area is 2.50×10-2 m2, and the thickness of the air layer is 5.10×10-5 m. What is the ratio of this force to the weight of the 0.360–kg cart?4. How much angioplasty is enough? Angioplasty is a technique in which arteries partially blocked with plaque are dilated to increase blood flow. By what factor must the radius of an artery be increased in order to increase blood flow by a factor of 8.0?

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