A 180–hp sports car of frontal area 1.72 m2, with a drag coefficient of 0.31, requires 17 hp to cruise at 100 km/h. At what speed does aerodynamic drag first exceed rolling resistance? The rolling resistance is 1.2 percent of the car weight, and the car mass is 1250 kg. Find the drivetrain efficiency. What is the maximum acceleration at 100 km/h? What is the maximum speed? Which redesign will lead to a higher maximum speed: improving the drive train efficiency by 6 percent from its current value, reducing the drag coefficient to 0.29, or reducing the rolling resistance to 0.91 percent of the car weight?
Want to see the full answer?
Check out a sample textbook solutionChapter 9 Solutions
Fox and McDonald's Introduction to Fluid Mechanics
Additional Engineering Textbook Solutions
Mechanics of Materials
Fundamentals Of Thermodynamics
Thinking Like an Engineer: An Active Learning Approach (4th Edition)
INTERNATIONAL EDITION---Engineering Mechanics: Statics, 14th edition (SI unit)
Thinking Like an Engineer: An Active Learning Approach (3rd Edition)
Degarmo's Materials And Processes In Manufacturing
- 7. A 2700-lb car is traveling @ sea level at a constant speed. Its engine is running at 4500 rev/min. and is producing 175 ft-lb of torque. It has a drivetrain efficiency of 90%, a drive axle slippage of 2%, 15-inch-radius wheels, and an overall gear reduction ratio of 3 to 1. If the car's frontal area is 21.5 ft, what is its drag coefficient?arrow_forwardQ1 A car is traveling at sea level at a constant speed. It weighs 2500-lbs, has a frontal area of 20 ft² and has a 90% drivetrain efficiency. Its engine runs at 4000 rev/min, producing 168 ft-lb of torque. The drive axle slippage of 2%, 14-inch-radius wheels, and an overall gear reduction ratio of 2.5 to 1. What is its drag coefficient?arrow_forwardA new sports car has a drag corfficient of 0.30 and a frontal area of 18.5 ft<, and is traveling at 90 mi/h. How much power (in ft-lb/s) is required to overcome aerodynamic drag if air density is 0.002378 slugs/ft?arrow_forward
- Determine the velocity required for take off for an aircraft with the following characteristics.Aircraft mass: 7200 kgWingspan: 15 mWing shape: rectangularWing chord length: 1.8 mWing airfoil: NACA 4415Wing angle of attack: 7× 0.5 + 5 degreesHint: Check NACA charts for required parameters.arrow_forwardA smooth square billboard 5 × 5 m² is place on a roof of a tall building. In orienting the billboard, the engineer is considering the wind direction for two possible cases: (a) the wind is parallel to the board (b) the wind is perpendicular to the board. Assuming maximum wind velocity of 10 m/s, what will be the force acting on the billboard in each of the cases considered? (Use u = 1.85 x 10-5 kg/m – s; p= 1.225 kg/m³; Recr = 500,000) %3Darrow_forwardThe large block shown is x = 72 cm wide, y = 54 cm long, and z = 9.0 cm high. This block is passing through air (density of air p = 1.43 kg/m³) at a speed of v = 8.61 m/s. Find the drag force F41 acting on the block when it has the velocity vj and a drag coefficient I = 0.812. V2 Fa.1 N %3D Find the drag force F42 acting on the block when it has the velocity vz with a drag coefficient I = 0.893. F42 N Find the drag force Fa.3 acting on the block when it has the velocity vz with a drag coefficient I = 1.06. F4.3 = N ENarrow_forward
- A NACA 2412 airfoil with a chord of 0.64m is flying in an airstream of standard sea level conditions. The freestream velocity is 70 m/s. Given the lift per unit span is 1,254 N/m. By using the experimental data for NACA 2412 data plot in Figure Q1c, investigatethe angle of attack of the airfoil and the analyze the value of drag per unit spanof the airfoil. Given that at standard sea level, ?=1.789×10-5 kg/m.s.arrow_forwardIf your lift to drag ratio is 15 for airline A flight and the airplane weighs 15,000-lb for L/Dmax, what’s the speed for L/Dmax at 22,500 lbs.?arrow_forwardA large transport aircraft shown below whose gross weight is 100,000 lb. The airplane pitching mass moment of inertia Iy=40,000,000 lb-s2 in. The airplane is making a level landing with the nose wheel slightly off the ground. The reaction on the rear wheels is 319,000 lbf inclined at such an angle to give a drag component of 100,000 lb and a vertical component of 300,000 lb. Determine: a) The intertial forces on the airplane. b)The resultant load on the pilot whose weight is 180 lbm and whose location is as given in the figure.arrow_forward
- A streamlined experimental solar car has a frontal area of 0.48 m² and an expected coefficient of drag of 0.12. The car and driver have a total mass of 200 kg. What is the maximum speed that could be expected if the maximum power available from its electric motor is 350 W? Assume a rolling resistance coefficient of 0.015. Take the density of air as 1.21 kg/m³.arrow_forward2. A 1500 kg electric vehicle travels along an asphalt roadway with a 5° grade at 100 km/h and a rolling resistance coefficient of 0.013. The frontal area is 2.05 m² and a drag coefficient is 0.32. The battery capacity is 85kWh and the battery nominal voltage is 320V. The air density of 1.2 kg/m3. (a) What is the power required to propel this vehicle? (b) The gear ratio is 10.7, the tire radius is 0.23m. Assume 100% efficiency for the gear. (i) What is the torque seen by the ac propulsion motor (ii) What is the power and speed of the motor? (c) What is the range of the vehicle considering 80% Depth of Discharge on a flat road at a speed of 50 km/h? 3. In the system of problem 2, the propulsion motor used is a star connected interior permanent magnet motor fed by a three phase IGBT inverter. The motor is operated in direct torque controlled mode. The inverter output voltage is 414V(L-L) and the modulation index is 0.9. The motor efficiency is 98% and power factor is 0.78. The dc link…arrow_forwardCurrent Attempt in Progress In the 1930s, the U.S. Navy operated dirigibles. The largest was the U.S.S. Akron with a length of 785 ft and a maximum diameter of 132 ft. Its maximum speed was 84 mph (123.2 ft/sec). Moving at top speed at 10,000 ft standard atmosphere, estimate the power required in horsepower to overcome the friction drag. Disregard effects of fins and other protrusions. Assume the surface of the dirigible is smooth and the friction drag is that over a flat plate. (Hint: "unwrap" the outer surface of the ship.) W = hparrow_forward
- Elements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University PressMechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSONThermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. BolesPublisher:McGraw-Hill Education
- Control Systems EngineeringMechanical EngineeringISBN:9781118170519Author:Norman S. NisePublisher:WILEYMechanics of Materials (MindTap Course List)Mechanical EngineeringISBN:9781337093347Author:Barry J. Goodno, James M. GerePublisher:Cengage LearningEngineering Mechanics: StaticsMechanical EngineeringISBN:9781118807330Author:James L. Meriam, L. G. Kraige, J. N. BoltonPublisher:WILEY