17.2. Slip Drag and Lift

Try these first

1. 1.

   Define drag force in your own words.

   Hint

   Think about what happens when you stick your hand out of a moving car window.

2. 2.

   What does the coefficient of drag (C_d) describe?

   Hint

   This coefficient varies from one shape to another.

3. 3.

   What does the coefficient of drag (C_d) depend on?

   • Shape of the body
   • Fluid density
   • Both A and B

   Hint

   Consider how different objects experience varying resistance.

4. 4.

   True or False: Lift force always acts in the same direction as the flow.

   • True
   • False

   Hint

   Remember how airplane wings generate lift.

5. 5.

   A car with a frontal area of 3 m² and a drag coefficient of 0.3 is traveling at 30 m/s. Calculate the drag force acting on the car.

   Hint

   Make sure to convert your units appropriately.

6. 6.

   If a cyclist can reduce their C_d from 0.9 to 0.6 by changing positions, quantify the potential speed increase if power output remains constant.

   Hint

   Consider the relationship between power, velocity, and drag.