# - All athletic events take place in fluid. Fluid dynamics studies the effects of human movement and projectiles through these fluid forces.

Mechanics

Oct 24, 2013 (4 years and 5 months ago)

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Fluid Mechanics

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157 of text and answer the following questions:

1)

What does fluid dynamics study?

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All athletic events take place in fluid. Fluid dynamics studies the effects of human
movement and projectiles through these fluid forces.

2)

Drag an
d lift forces are what to each other?

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Perpendicular

3)

What is flow velocity?

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The motion of fluid flowing past an object or motion of object through the fluid.

4)

What is drag? What is the difference between profile drag and skin
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friction drag?

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Resistance
through fluid

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Profile drag is drag caused by shape of object

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Skin
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friction drag is drag caused by the roughness of a surface

5)

What are both skin
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friction and profile drag proportional to
? Which most often occurs
in sport?

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Skin
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friction and profile drag are
proportional to relative flow velocity, cross
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sectional area, shape of object, smoothness of surface, and density of liquid

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Profile drag is the source of most drag in sport

6)

What is the difference between laminar flow and turbulent flow?

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Laminar flow is smo
oth and layered

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Turbulent flow is disordered, eddied,
and non
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layered

7)

Why does turbulence increase the amount of work done on an object?

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The region of low pressure created by turbulence must be carried along

8)

Describe how shape and equipment design help s
peed skaters and lugers overcome
drag?

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Crouch, egg shape, arms back (speedskaters)

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Helmet shape, sled shape

9)

Where can lift forces be directed?

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Up (discus, ski jumpers), down (topspin), sideways (curveball)

10)

How does lift occur?

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Air flows faster over one

side of an object, creating a difference in pressure

11)

What is Bernoulli’s principle?

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Movement occurs from area of high pressure to area of low pressure

12)

What is the angle of attack? What is the stall angle?

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Angle of attack is the tilt of an object relat
ive to flow velocity. Allows object to
lift and remain airborne longer

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Stall angle is the angle at which the drag force overcomes the lift force
. Object
will fall at this point.

13)

Describe the Magnus effect.

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Spinning ball creates turbulence

on one side
, tu
rbulence creates low pressure area,
object moves from area of high pressure to area of low pressure

14)

Draw a simple diagram that illustrates the Magnus effect. (see. Fig. 7.16)

15)

How does topspin/backspin affect horizontal distance?

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Topspin shortens horizont
al distance, and backspin lengthens horizontal distance

16)

What direction does a ball break with sidespin?

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The direction the ball is spinning

17)

Why is the Magnus effect most readily seen in tennis, golf, ping
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pong, baseball?

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Objects have large enough cross
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sectional area, are light

& small

(can spin more,
increasing flow velocity), have rough surfaces (tennis, baseball, golf)

18)

How does the design of a baseball allow for a curveball to be thrown?

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Stitches

Wiffeball
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