Concept explainers
The drag coefficient of a vehicle increases when its windows are rolled down or its sunroof is opened. A sports car has a frontal area of 18 ft2 and a drag coefficient of 0.32 when the windows and sunroof are closed. The drag coefficient increases to 0.41 when the sunroof is open. Determine the additional power consumption of the car when the sunroof is opened at (a) 35 mi/h and (b) 70 mi/h. Take the density of be to be 0.075 Ibm/ft3.
(a)
The additional power consumption of the car when the roof opened at
Answer to Problem 41EP
Explanation of Solution
Given information:
Concept used:
Calculation:
Conclusion:
The additional power consumption of the car when the roof opened at
(b)
The additional power consumption of the car when the roof opened at
Answer to Problem 41EP
Explanation of Solution
Given information:
Concept used:
Calculation:
Conclusion:
The additional power consumption of the car when the roof opened at
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Chapter 11 Solutions
Fluid Mechanics: Fundamentals and Applications
- An airplane is consuming fuel at a rate of 7 gal/ min when cruising at a constant altitude of 10,000 ft at constant speed. Assuming the drag coefficient and the engine efficiency to remain the same, determine the rate of fuel consumption at an altitude of 30,000 ft at the same speed.arrow_forwardA commercial airplane has a total mass of 150,000 lbm and a wing planform area of 1700 ft2. The plane has a cruising speed of 625 mi/h and a cruising altitude of 38,000 ft where the air density is 0.0208 lbm/ft3. The plane has double-slotted flaps for use during takeoff and landing, but it cruises with all flaps retracted. Assuming the lift and drag characteristics of the wings can be approximated by NACA 23012, determine (a) the minimum safe speed for takeoff and landing with and without extending the flaps, (b) the angle of attack to cruise steadily at the cruising altitude, and (c) the power that needs to be supplied to provide enough thrust to overcome drag. Take the air density on the ground to be 0.075 lbm/ft3.arrow_forwardBill gets a job delivering pizzas. The pizza company makes him mount a sign on the roof of his car. The frontal area of the sign is A = 0.612 ft2, and he estimates the drag coefficient to be CD = 0.94 at nearly all air speeds. Estimate how much additional money it costs Bill per year in fuel to drive with the sign on his roof compared to without the sign. Use the following additional information: He drives about 10,000 miles per year at an average speed of 45 mph. The overall car efficiency is 0.332, ? fuel = 50.2 lbm/ft3, and the heating value of the fuel is 1.53 × 107 ft . lbf/lbm. The fuel costs $3.50 per gallon. Use standard air properties. Be careful with unit conversions.arrow_forward
- A commercial airplane has a total mass of 70,000 kg and a wing planform area of 150 m2. The plane has a cruising speed of 558 km/h and a cruising altitude of 12,000 m, where the air density is 0.312 kg/m3. The plane has double-slotted flaps for use during takeoff and landing, but it cruises with all flaps retracted. Assuming the lift and the drag characteristics of the wings can be approximated by NACA 23012 , determine (a) the minimum safe speed for takeoff and landing with and without extending the flaps, (b) the angle of attack to cruise steadily at the cruising altitude, and (c) the power that needs to be supplied to provide enough thrust to overcome wing drag.arrow_forwardTo reduce the drag coefficient and thus to improve the fuel efficiency, the frontal area of a car is to be reduced. Determine the amount of fuel and money saved per year as a result of reducing the frontal area from 17 to 14 ft2. Assume the car is driven 10,000 mi a year at an average speed of 55 mi/h. Take the density and price of gasoline to be 50 lbm/ft3 and $3.10/gal, respectively; the density of air to be 0.075 lbm/ft3; the heating value of gasoline to be 20,000 Btu/lbm; and the overall efficiency of the engine to be 30%.arrow_forwardThe rectangular wings of a microlight aircraft have a combined spanwise length of 9.144 m and streamwise (direction of air flow) width of 0.9144 m The wings have a coefficient of form drag of 0.01 and a lift coefficient of 0.3 in cruise. When cruising at a speed of 150km/h and altitude of 3,000 feet, the temperature and absolute pressure of the atmospheric air are 5°C and 90 kPa, respectively.arrow_forward
- To reduce the drag coefficient and thus to improve the fuel efficiency, the frontal area of a car is to be reduced. Determine the amount of fuel and money saved per year as a result of reducing the frontal area from 20 to 13 ft2. Assume the car is driven 12,000 mi a year at an average speed of 55 mi/h. Take the density and price of gasoline to be 50 lbm/ft3 and $3.10/gal, respectively; the density of air to be 0.075 lbm/ft3, the heating value of gasoline to be 20,000 Btu/lbm; and the overall efficiency of the drive train to be 30 percent.arrow_forwardTo reduce the drag coefficient and thus to improve the fuel efficiency, the frontal area of a car is to be reduced. Determine the amount of fuel and money saved per year as a result of reducing the frontal area from 18 to 15 ft2. Assume the car is driven 12,000 mi a year at an average speed of 55 mi/h. Take the density and price of gasoline to be 50 lbm/ft3 and $3.10/gal, respectively; the density of air to be 0.075 lbm/ft3; the heating value of gasoline to be 20,000 Btu/lbm; and the overall efficiency of the engine to be 30 percent.arrow_forwardAn airplane is cruising at a velocity of 950 km/h in air whose density is 0.526 kg/m3. The airplane has a wing planform area of 90 m2. The lift and drag coefficients on cruising conditions are estimated to be 2.0 and 0.06, respectively. The power that needs to be supplied to provide enough trust to overcome wing drag is (a) 21,500 kW (b) 19,300 kW (c) 23,600 kW (d ) 25,200 kW (e) 26,100 kWarrow_forward
- The drag coefficient of a car at the design conditions of 1 atm, 70°F, and 60 mi/h is to be determined experimentally in a large wind tunnel in a full-scale test. The frontal area of the car is 22.26 ft2. If the force acting on the car in the flow direction is measured to be 68 lbf, determine the drag coefficient of this car.arrow_forward, A small aircraft has a wing area of 40 m2a lift coefficient of 0.45 at takeoff settings, and a total mass of 4000 kg. Determine (a) the takeoff speed of this aircraft at sea level at standard atmospheric conditions, (b) the wing loading, and (c) the required power to maintain a constant cruising speed of 360 km/h for a cruising drag coefficient of 0.035.arrow_forwardThe form drag coefficient of a certain light aircraft is equal to 0.011. Its skin friction drag coefficient is 0.016. Determine its lift-to-drag ratio (nearest hundredths) while flying at the speed for minimum power required if its interference drag is 7 percent of its profile drag. The aircraft has rectangular wing with an aspect ratio of 7.01. Assume a a span efficiency factor of 0.91.arrow_forward
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