Page 422: Questions # 1 to 9 inclusive [answers in bold print]

1.    Under which condition would you experience more resistive drag?
    a.    You're running at 10mph in still air?
    b.    You're running at 8mph with a 2mph tailwind.
    c.    You're running at 7mph with a 2mph headwind.
Explain your answer.

The relative flow dictates the drag force you experience.  The relative flow in (a) is 10mph, in (b) 6mph, in (c) 9mph, so the drag is greatest in (a).

2.    Which factor in the drag equation affects the magnitude of drag force more than the others?  Why?

The velocity of fluid flow is most influential because it is squared (if you double the velocity, you quadruple the drag force).

3.    How do the coefficients of drag of a basketball and a softball compare?  If both were moving at the same speed through the air, which would experience a greater drag force?  Explain your answers.

Because a softball and basketball have the same shape, their drag coefficients would be the same with slight variation due to surface qualities.  At the same speed through the air, the basketball would experience more drag because of its greater area facing the relative flow.

4.    Of the two types of fluid drag, which one accounts for the greatest part of the total drag acting on the body or implement in sport activities?

Profile drag.

5.    What is the boundary layer?  What is meant by boundary layer separation?

The boundary layer is the layer of fluid surrounding a body or object moving through a fluid that moves with the surface of the object and experiences friction forces from the fluid layers traveling past it.  On slowly moving objects, it clings to the trailing surfaces of a body, but as speed increases, it is pulled away from the trailing surfaces near the widest part of the object and this creates a low pressure region (suction) on the rear portions of the object.

6.    Describe the difference between a fluid's density and its viscosity.

Density is the ""compactness"" of a fluid, mass/volume.  Viscosity is the fluid's internal resistance to being deformed, or how much it ""clings"" to itself, or resists being poured.

7.    In what direction is air flowing past a ball at the instant it is projected at forty-five degrees above the horizontal?  What effect does the drag have on the ball's vertical and horizontal release velocity?

Air flow is in the opposite direction of the ball's motion, so it is 45 degrees below the horizontal.  This drag force can be resolved into its horizontal and vertical components which will be equal in magnitude and will therefore affect the ball's velocity components equally.  The downward drag component, however, acts with gravity to decelerate the ball's upward movement more than its forward movement.

8.    What is the direction of air flow past the ball in question 7 when it reaches the peak of its flight path?  What is the effect of the drag force on the ball at the peak?

At the peak of the ball's path, the air flow and drag is all horizontal, acting to decelerate forward motion.

9.    How does streamlining affect the air flow past a body so that drag is decreased?

Streamlining a body allows the air flow to pass more smoothly along the body and behind it so that a relatively small low pressure (suction) zone is created.

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Page 426: Questions # 1 to 4 inclusive [answers in bold print]

1.    State Bernoulli's principle relating pressure to velocity of fluid flow.

The pressure in a fluid varies inversely with that fluid's velocity.  Slower flow has greater pressure than faster flow.

2.    In which direction relative to fluid flow direction past a wing-shaped body does lift force act?

Fluid lift force is directed perpendicular to the flow velocity past a wing-shaped body.

3.    Describe how a difference in pressure occurs on opposite sides of a lift-producing body.

If fluid flows past a body such that opposite sides of the body experience different flow velocities, the corresponding fluid pressures will be different, also, according to Bernoulli's principle.  The side with the higher pressure is forced into the direction of the side with lower pressure.

4.    Sketch a wing-shaped body moving through a fluid so that a lift force acts on it in a downward direction.
 
Refer to Figure K.8 on page 423 and hold the picture upside down to reveal how the object must be oriented relative to fluid flow in order to obtain a downward lift force.