Determine the horsepower required to overcome the wind drag on a streamlined car traveling 90 km/h if the drag coefficient C D is 0.2. The drag force is given by F D = ½ ρ V 2 AC D , where A is the projected area of the car and V is the velocity. The density ρ of air is 1.23 kg/m 3 . Use A = 2.3 m 2 .
Text Solution
Verified by ExpertsCHECK THE SOLUTION.
Sol. To find the drag force on a car we must express the velocity in m/s; V = (90) (1000/3600) = 25 m/s. The drag force is then
F D = ½ ρ V 2 AC D
= (½) (1.23) (25 2 ) (2.3) (0.2) = 177 N
To move this drag force at 25 m/s the engine must do work at the rate
W = F D V = (177) (25) = 4425 W
The horsepower is then
H p = 
= 5.93 hp
Prepare Smarter with CGP Edu
Get practice questions, solutions, and test series in one place.
Write a Review
Share your experience with this question and solution.
Commentary
Send your comment, doubt, correction, or feedback to admin.
Similar Questions
Explore conceptually related problems