HW#6 Chp 4 and Chp 5 Begin Date: 2/12/2018 12:01:00 AM-Due Date: 2/19/2018 11:59
ID: 1873434 • Letter: H
Question
HW#6 Chp 4 and Chp 5 Begin Date: 2/12/2018 12:01:00 AM-Due Date: 2/19/2018 11:59:00 PM End Date: 5/4/2018 11:59:00 PN (9%) Problem 10: 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 121 kgm3 Randomized Variables s1 -78 km/h 52 = 102 km/h 25% Part (a) what is the drag force at 78 km/h for a Toyota Camry? (Drag area is 0.70 m2) FD= Grade: Deduct Potentia 4 5 6 1 2 3 Submis Attempt per detailed cotan asin acos0 atan) acotan0sinh0 coshO tanh0 cotanh0 °Degrees Radians Submit Hint I give up Hints:-% deduction per hint. Hints remaining: 2 Feedback: 1% deduction per feedback. 25% Part (b) what is the drag force at 102 km/h for a Toyota Camry? (Drag area is 0.70 m2) 25% Part (c) what is the drag force at 78 km/h for a Hummer H2? (Drag area is 2.44 m2) 25% Part (d) what is the drag force at 102 km/h for a Hummer H2? (Drag area is 2.44 m2)Explanation / Answer
The drag force is given as, F = cApv^2
where c=drag coefficient, p=density, v=speed, A=drag area
Now, 78km/hr=(78*5/18)m/s (1km/hr = 5/18 m/s)
= 21.67 m/s
& 102km/hr = (102*5/18) m/s = 28.34 m/s
(a) Here, F = [0.28*0.70*1.21*(21.67)^2] N
= 111.37 N
(b) In this case, F = [0.28*0.70*1.21*(28.34)^2] N
= 190.48 N
(c) Here, F = [0.64*2.44*1.21*(21.67)^2] N
= 887.31 N
(d) In this case, F = [0.64*2.44*1.21*(28.34)^2] N
= 1517.59 N
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