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/m3.
(a) What are the drag forces in newtons at 77 km/h and 106 km/h for a Toyota Camry? (Drag area = 0.70 m2 and drag coefficient = 0.28.) at 77 km/h N at 106 km/h N
(b) What are the drag forces in newtons at 77 km/h and at 106 km/h for a Hummer H2? (Drag area = 2.44 m2 and drag coefficient = 0.57.) at 77 km/h N at 106 km/h N Supporting Materials

[tex]V= 77 \frac{km}{h}* \frac{1h}{3600 s} *\frac{1000m}{1 km} = 21.38 \frac{m}{s} \\V=106 \frac{km}{h}* \frac{1h}{3600 s} *\frac{1000m}{1 km} = 29.44 \frac{m}{s}[/tex]

a).

ρ[tex]= 1.2 \frac{kg}{m^{3} }[/tex], [tex]A_{t}= 0.7 m^{2}[/tex], [tex]D_{t}= 0.28[/tex]

[tex]F_{t1} = \frac{1}{2} * D_{t} * A_{t}* p_{t}* v_{t}^{2}[/tex]

[tex]F_{t1} = \frac{1}{2} * 0.28 * 0.7m^{2} * 1.2\frac{kg}{m^{3} }* 21.38^{2}= 53.75 N [/tex]

[tex]F_{t1} = \frac{1}{2} * 0.28 * 0.7m^{2} * 1.2\frac{kg}{m^{3} }* 29.44^{2}= 101.92 N [/tex]

b).

ρ[tex]= 1.2 \frac{kg}{m^{3} }[/tex], [tex]A_{h}= 2.44 m^{2}[/tex], [tex]D_{h}= 0.57[/tex]

[tex]F_{t1} = \frac{1}{2} * D_{h} * A_{h}* p_{h}* v_{h}^{2}[/tex]

[tex]F_{t1} = \frac{1}{2} * 0.57 * 2.44 m^{2} * 1.2\frac{kg}{m^{3} }* 21.38^{2}= 381.44 N [/tex]

[tex]F_{t1} = \frac{1}{2} * 0.57 * 2.44 m^{2} * 1.2\frac{kg}{m^{3} }* 29.44^{2}= 723.25 N [/tex]