14.11. As we explained in Chapter 7, the air resistance to motion of a vehicle is something important that engineers investigate. As you may also know, the drag force acting on a car is determined experimentally by placing the car in a wind tunnel. The air speed inside the tunnel is changed, and the drag force acting on the car is measured. For a given car, the experimental data is generally represented by a single coefficient that is called drag coefficient. It is defined by the following relationship: Fa Cả where Ca = drag coefficient (unitless) Fa = measured drag force (N or 1b) p= air density (kg/m³ or slugs/ft') V = air speed inside the wind tunnel (m/s or ft/s) A = frontal area of the car (m? or ft') The frontal area A represents the frontal projection of the car's area and could be approximated simply by multiplying 0.85 times the width and the height of a rectangle that outlines the front of a car. This is the area that you see when you view the car from a direction normal to the front grills. The 0.85 factor is used to adjust for rounded comers, open space below the bumper, and so on. To give you some idea, typical drag coefficient values for sports cars are between 0.27 to 0.38, and for sedans are between 0.34 to 0.5. The power requirement to overcome air resistance is computed by P= F,V where P= power (watts or ft· lb/s) 1 horse power (hp) = 550 ft lb/s and 1 horse power (hp) = 746 W The purpose of this exercise is to see how the power requirement changes with the car speed and the air temperature. Determine the power requirement to overcome air resistance for a car that has a listed drag coefficient of 0.4 and width of 74.4 in. and height of 57.4 in. Vary the air speed in the range of 15 m/s < V < 35 m/s, and change the air density range of 1.11 kg/m³

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A 10-ft long cylinder with a diameter of 7 ft floats in oil (SG = 0.60) and rests against a wall as shown in the figure below. What is the horizontal force the cylinder exerts on the wall at the point of contact A? What is the vertical force of fluid on the cylinder? Express answers in lbf.

The air resistance to the motion of a vehicle is something important that engineers investigate. As you may also know, the drag force acting on a car is determined experimentally by placing the car in a wind tunnel. For a given car, the experimental data is generally represented by a single coefficient that is called the drag coefficient. It is given by the relationship: Fa C, = where C, = drag coefficient F, = measured drag force (Ib) p = air density (slugs/ft') V = air speed inside the wind tunnel (ft/s) A = frontal area of the car (ft²) What is the appropriate unit for C, if the preceding equation is to be homogeneous in units? Show all steps of your work.