Question

1191 One day Daniel Bernoulli was sitting in a Starbucks sipping on a Venti Mocha Frappuccino. He pondered some of the many applications of his newly developed principle. Grab a Starbucks of your own, and help him to answer the following questions. Assume air weighs 0.081 lb/ft3 NOTESIMAGES DISCUSS UNITS STATS HELP Part Description Answer Chk History In a hurricane, roofs of structures are really lifted off, and not blown off, due to the decreased pressure as the wind blows over the roof Determine the required wind speed to lift a roof that weighs 39 psf Assume the roof is not tied down. (include units with answer) 18.33 pts. 110% # tries: 0 Show Details A. Format Check -12%try penalty Hints: 1,0 Determine the minimum required take-off speed of a 28000 pound UScairways jet with a wing area of 1380 ft2. Use a lift coefficient of K-0.12 (include units with answer) 18.33 pts. 110% # tries: 0 Show Details B. Format Check 2% try penalty Hints: 1O Daniel's good friend Giovanni Venturi joined him for another round of fraps. They were discussing ways to determine the velocity of water in a pipe. If the pressure drops 690 kPa as water flowing in a 40 cm diameter pipe is forced to flow through a 10 cm diameter portion, what is the velocity of the water in the 40 cm section of pipe? include units with answer | 18.33 pts, 110% 2% try penalty C. Format Check # tries: 0 Show Details Hints: 1, Previous Next

Answer 1

(A) Weight of roof = 35 psf By Bernaullis� equation PA + 1/2 rho V A^2 = P_B + 1/2 rho V^2 B rightdoublearrow 1/2 rho V^2 = P = 35 psf = 1675.80 Pa and rho = 0.081 lb/ft^3 rho = 1.2975 kg/m^3 rightdoublearrow 1/2 times 1.2975 times V^2 = 1675.8 rightdoublearrow V = 50 .82 m/s (B) Lift force = c rho V^2/2 A ohm rightarrow coefficient therefore F rightdoublearrow 27000 times 0.454 times 9.8 = 0.12 times 1.2975 times V^2/2 times 131.92 rightdoublearrow V = 107.675 m/s (C) P_A + 1/2 PV^2_1 = P_B + 1/2 times V^2_2 A_1 V_1 = A_2 V_2 rightdoublearrow pi (49/2)^2 times V_1 = pi (18/2)^2 times V_2 rightdoublearrow V_2 = (49/18)^2 V_1 therefore P_A - P_B = 1/2 rho (V^2_2 - V^2_1) therefore 850 times 10^3 = 1/2 times 1000 V^2_1 [(49/18)^2 - 1] rightdoublearrow V = 5.62 m/s