Question

Lecture I1.3. Drag Force 267 26 percent of greenhouse gas emissions come from cars, with a typical passeng emitting about 4.7 metric tons of carbon dioxide per year. Assuming all of the rom overcoming air resistance (ignoring internal resistances and stopping/starting much would we need to reduce the 70 mph speed limits vehicle emissions are how to obtain a 20 percent cut in greenhouse er emissions from cars? 14. A small particle with a radius of 0.1 mm and drag coefficient of 1 is moving (density of 1.21 kg/m3 and viscosity of 18.1 uPas). At what velocity wi through air force for igher velocity flow (sometimes called the quadratic drag force) be equal to the low velocity drag force (from Stoke's law)? 15. A skydiver is falling at a terminal velocity of 57 m/s before opening her parachute. After opening her parachute, she falls at a much smaller terminal velocity of 5 m/s. How does the upward force before she opens her parachute compare to the her parachute? total total upward force after she opens 16. Fish may swim in collectively oriented streams, balls, or rings, and these motions are to assist in foraging and in avoiding predators. Each individual can swimming in the slipstream of another fish. In effect moving with the fish. Consider a fish swimming at 1 m/s in fresh water with a dag coeficient 0.8 and a cross-sectional area in the direction of motion of 1 × 10-7m. How drag force be reduced if swimming with a school of fish that creates a flow of water of around the fish? ed improve its efficiency by the velocity of the water around the fish is much would its 0.5 m/s 17. Dolphins have little tear drops in their skin which traps some water so water flows over the water that is trapped. The skin feels soft and flaky, and sheds every two hours. This helps dolphins swim through the sea water at high speed. A 59% reduction in drag coefficient has been reported to be due to removing the effects of the microstructure of the dolphins skin (this is esti- mated from artificial rubber bioinspired membranes). Dolphins can swim as fast as 7.7 m/s, but if the dolphin's skin didn't have the microstructural effects what might be the dolphin's top speed?

Answer 1

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