Question

1)What is the drag force on a 1.6 m wide, 1.4 m high car traveling at 10 m/s (? 22 mph)? Suppose that the density of air is 1.2 kg/m3.

2)What is the drag force on a 1.6 m wide, 1.4 m high car traveling at 30 m/s (? 67 mph)? Suppose that the density of air is 1.2 kg/m3.

Answer 1

Here is the answer

F = -1/2 rho A Cd v^2 where rho = density , A = cross sectional area
Cd = drag coefficient ( a number between 0 and 1 that depends on the shape of the object)
for air:
rho is about 1.3x10^-3 g/cm^3 or 1.3kg/m^3
F in newtons is -1/2 * 1.3kg/m^3 * 1.6m *1.4m *(10m/s)^2 * Cd
F = -145.6 Cd newtons unless you are given Cd that is as far as you can go

2nd part: v is 3 times larger and it gets squared in the drag force equation so the drag force is 9 times greater at 30m/s