To maintain a constant speed, the force provided by a car\'s engine must equal t
ID: 1418170 • Letter: T
Question
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). The density of air is 1.2 kg/m^3. What are the drag forces at 75 km/h and 103 km/h for a Toyota Camry? (Drag area = 0.70 m^2 and drag coefficient = 0.28.) at 75 km/h 54.86 Recall that the drag force is proportional to the square of the velocity. Check for consistency in units. N at 103 km/h 97.59 N What are the drag forces at 75 km/h and 103 km/h for a Hummer H2? (Drag area = 2.44 m^2 and drag coefficient = 0.57.) at 75 km/h 389.33 Recall that the drag force is proportional to the square of the velocity. Check for consistency in units. N at 103 km/h 692.53 N raindrop 2.1 mm in diameter falls through a vertical distance of 4000 m. Take the cross-sectional area of a raindrop = pi r^2, drag coefficient = 0.45, density of water to be of air to be 1.2 kg/m^3. Calculate the speed a spherical raindrop would achieve falling from 4000 m in the absence of air drag. 286.91 In the absence of air drag the object is in free fall m/sExplanation / Answer
density of air = da= 1.225 kg/m^3. To convert x km/hr to m/s we multiply 5/18 so it becomes x *5/18 m/s
a.
At 75 km/hr
drag force = 1/2 x density of air x drag co-eff x surface area x velocity^2
= 1/2 x 1.225 x 0.28 x 0.7 x (75 x 5/18)^2
= 52.08 N
at 103 km/hr
drag force = 1/2 x density of air x drag co-eff x surface area x velocity^2
= 1/2 x 1.225 x 0.28 x 0.7 x (103 x 5/18)^2
= 98.27 N
b. At 75 km/hr
drag force = 1/2 x density of air x drag co-eff x surface area x velocity^2
= 1/2 x 1.225 x 0.57 x 2.44 x (75 x 5/18)^2
= 369.73 N
At 103 km/hr
drag force = 1/2 x density of air x drag co-eff x surface area x velocity^2
= 1/2 x 1.225 x 0.57 x 2.44 x (103 x 5/18)^2
= 697.33 N
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