Page 457: Questions # 1 to 4 inclusive [answers in bold print]

1.    Review Archimedes' principle.

Archimedes' principle states that the magnitude of the buoyant force applied by the water to a wholly or partially immersed body is equal to the weight of the volume of water that is displaced byt he body.  This applies to any fluid.

2.    What happens to the average weight density of the body when a full inspiration is made?  Why?

When a full inspiration is made, the thorax volume increases significantly, but the weight of air inspired is negligible.  With the weight of the whle body remaing essentially the same, but the body's volume increased, the average density of the body is decreased.  (D=W/V)

3.    State what characterizes a conditional floater.

A conditional floater is one who will be supported at the survace only with some inspiration and who will sink upon expiration.  Such a person has a body density approximately equal to that of water, so that an inspiration wil cause body density to be less than that of water (permitting floating), and an expiration will cause body density to be more than that of water (causing sinking).  Most people are conditional floaters.

4.    Who is more likely to float; a lean female weighing 668 N (150lb) or an obese male weighing 801 N (180 lb)?  Why?

An obese male will be more likely to float than a lean female who weighs less because his density is more likely to be less than that of water (fat is less dense than muscle and water).  Weight is not the determining factor; body density is.

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Page 465: Questions # 1 and 2 [answers in bold print]
 

1.    Name and describe each of the three types of drag force that can resist the forward body motion of a swimmer.

Profile drag, skin friction, and wave drag ar the three types of drag force affecting the motion of a swimmer.

2.    Why would a "sinker" sink faster in a vertical position than in a horizontal position?

A sinker would sink faster in a vertical position than in a horizontal position because a smaller area would be facing the upward flow of water as the body descended, and the drag force is proportional the the area facing the flow.

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Page 484: Questions # 1 to 4 inclusive [answers in bold print]

1.    Explain how drag force can serve as a propulsive force in  swimming.

Any movement of a body segment that moves backward relative to the watyer, thus creating a forward-directed flow past the segment, creates a forward-directed drag force on that segment.  Therefore, any forward-directed drag force on a body segment is propulsive in that force is in the same direction as intended body travel.

2.    Explain how lift force is produced on the hand moving through water.

Lift force is produced on a hand moving through the water as a wing, or hydrofoil, so that a pressure difference occurs between the opposite surfaces of the hand.  This is accomplished by blading the hand through the water with an angle of atack relative to the flow past the hand.  The lift force is directed perpendicular to the flow direction past the hand.

3.    Explain how lift force on the hand can be used to support weight above the surface of the water.

As in treading water, the hands are bladed horizontally through the water inward with an angle of attack and outward with an angle of attack, so that the lift force is directed upward, perpendicular, to the paths of the hands.  Stabilizing at the shoulder joints, so that the upward lift force does not drive the hands up out of the water, the head is supported out of the water.  In synchronized swimming skills, this sculling action is used extensively to support and lift other body segments above the surface; for example, on er both legs, or one arm, or combinations of different body segments.

4.    Explain how lift force can prevent the hand from moving backward through the water in a front crawl stroke.  Is this desirable?  Why?

Just as lift force acts upward on the hands in treading water, lift force acts forward on the blading hand in a front crawl stroke.  If this lift force is great enough, the body will be pulled forwoard through the water toward the arm when the shoulder muscles shorten, rather than the arm being moved backward through the water toward the body.  Such a propulsive mechanism is more efficient than that which is based on creating propulsive drag force on the hand, because less backward hand movements and more forward body movement occurs relative to the water.