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(8%) Problem 13: To maintain a constant speed, the force provided by a car\'s en

ID: 1779376 • Letter: #

Question

(8%) Problem 13: To maintain a constant speed, the force provided by a car's engine must equal the drag force plus the force of friction of the road (the rolling resistance). Assume that the drag coefficient for a Toyota Camry is 0.28, while for a Hummer it is 0.64. The density of air at this temperature is 1.21 kg/m Randomized Variables S, 68 km/h $2 = 92 km/h 25% Part (a) What is the drag force at 68 km/h for a Toyota Camry? (Drag area is 0.70 m2) Grade Deducti Potentia Submis Attempt (3% pe detailed sin) tan() | | cosO cotanasinacos0 atan)acotan() sinh) 0 cosh0 tanh) cotanhO Degrees Radians END BACKSPACE DEL CLEAR Submit Hint I give up! Hints: 0% deduction per hint. Hints remaining: 2 Feedback: 0% deduction per feedback 25% Part (b) What is the drag force at 92 km/h for a Toyota Camry? (Drag area is 0.70 m2) 25% Part (c) what is the drag force at 68 km/h for a Hummer H2? (Drag area is 2.44 m2) 25% Part (d) What is the drag force at 92 km/h for a Hummer H2? (Drag area is 2.44 m2)

Explanation / Answer

given drag coefficient for Toyota, Cd = 0.28

drag coefficient for hummer, Cd' = 0.64

debsity of air, rho = 1.21 kg/m^3

1. drag force at v = 68 km/h = 18.889 m/s for Cd = 0.28 and A = 0.7 m^2

Fd = 0.5*rho*v^2*A*Cd = 0.5*1.21*18.889^2*0.7*0.28 = 42.30867 N

2. drag force at v = 92 km/h = 25.5556 m/s for Cd = 0.28 and A = 0.7 m^2

Fd = 0.5*rho*v^2*A*Cd = 0.5*1.21*25.556^2*0.7*0.28 = 77.4456 N

3. drag force at v = 68 km/h = 18.889 m/s for Cd = 0..64 and A = 2.44 m^2

Fd = 0.5*rho*v^2*A*Cd = 0.5*1.21*18.889^2*2.44*0.64 = 337.087 N

4. drag force at v = 92 km/h = 25.5556 m/s for Cd = 0.64 and A = 2.44 m^2

Fd = 0.5*rho*v^2*A*Cd = 0.5*1.21*25.556^2*2.44*0.64 = 617.0366 N