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/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

Answer 1

a). 53.75 N and 101.92 N

b). 381.44 N and 723.25 N

Step-by-step explanation:

`V= 77 (km)/(h)* (1h)/(3600 s) *(1000m)/(1 km) = 21.38 (m)/(s) \\V=106 (km)/(h)* (1h)/(3600 s) *(1000m)/(1 km) = 29.44 (m)/(s)`

a).

ρ
`= 1.2 (kg)/(m^(3) )`,
`A_(t)= 0.7 m^(2)`,
`D_(t)= 0.28`

`F_(t1) = (1)/(2) * D_(t) * A_(t)* p_(t)* v_(t)^(2)`

`F_(t1) = (1)/(2) * 0.28 * 0.7m^(2) * 1.2(kg)/(m^(3) )* 21.38^(2)= 53.75 N`

`F_(t1) = (1)/(2) * 0.28 * 0.7m^(2) * 1.2(kg)/(m^(3) )* 29.44^(2)= 101.92 N`

b).

ρ
`= 1.2 (kg)/(m^(3) )`,
`A_(h)= 2.44 m^(2)`,
`D_(h)= 0.57`

`F_(t1) = (1)/(2) * D_(h) * A_(h)* p_(h)* v_(h)^(2)`

`F_(t1) = (1)/(2) * 0.57 * 2.44 m^(2) * 1.2(kg)/(m^(3) )* 21.38^(2)= 381.44 N`

`F_(t1) = (1)/(2) * 0.57 * 2.44 m^(2) * 1.2(kg)/(m^(3) )* 29.44^(2)= 723.25 N`