Question

The drag coefficient of a car at the design conditions of 1 atm,25 ∘C, and 90 km/h is to be determined experimentally in a large wind tunnel in a full-scale test. The height and width of the car are 1.25 m and 1.65 m, respectively. If the horizontal force acting on the car is measured to be 220 N, determine the total drag coefficient of this car. [ density of air rho=1.164 kg/m³

(a) Cd=2.3
(b) Cd=3
(c) Cd=4
(d) Cd=5
(e) Cd=6
(f) None of the above

Answer 1

The total drag coefficient of the car is approximately 2.0. Hence the correct answer is option A

Step-by-step explanation:

To determine the total drag coefficient of the car, we need to calculate the drag force first. The drag force can be calculated using the formula: Drag Force = 0.5 * Drag Coefficient * Density * Velocity^2 * Area. The area can be calculated by multiplying the height and width of the car. From the given data, the area of the car is 1.25 m * 1.65 m = 2.0625 m². Plugging in the values, we can rearrange the formula to solve for the drag coefficient. The drag force of the car is given as 220 N, the density of air is 1.164 kg/m³, the velocity is 90 km/h which is equal to 25 m/s. Solving the equation using these values, we get the drag coefficient as approximately 1.978. Therefore, the total drag coefficient of the car is approximately 2.0 (rounded to 1 decimal place).

Hence the correct answer is option A