Solution manual for the physics of sports 1st edition by lisa

No reproduction or distribution without the prior written consent of McGraw-Hill Education.. No reproduction or distribution without the prior written consent of McGraw-Hill Education..

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Chapter 1 Chapter 1 Problems

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CHAPTER 1 CHAPTER 1 PROBLEMS 2

1 Express the following distances in meters, using scientific notation: (a)the length of a football field; (b) the distance of a marathon (26 miles+ 384 yards); (c) a good basketball player’s vertical (40 inches)

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2 Choose the slowest among the following speeds: 220 ft/s, 100 mph, 70m/s, 300 km/hr, 70 yd/s

must put all in same units , to compare numerically

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3 An excellent time for the 1500-m race is 3 minutes 31.4 s Express thistime in (a) minutes and (b) seconds

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4 Europeans often brag that they drive 100 – 100 km/hr, that is Howfast is this, in (a) mph? (b) ft/s?

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5 Express Terrelle Pryor’s weight (233 lb) in Newtons (See Appendix ??

for conversion factors.)

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6 Figure 1.1 shows a woman touching her toes.

a) Why does she instinctively angle her legs backward away from tical?

ver-b) Try, yourself, to touch your toes (or reach for them, anyway) withlegs straight and vertical To make sure they remain vertical (i.e theydon’t tilt backward like the woman’s), stand with your heels against awall and then bend over Your body and instinct will teach you thisimportant point more convincingly than will any book

c) In January, 2008, the New York Times ran a story about Asheville’s basketball player Kenny George, 70 700 tall (!!!) Ashevillehas a contract with Nike, who made 12 pairs of size-26 shoes for George

UNC-The formula for American men’s shoe size isSize = 3⇥ length in inches 24

If the woman in the figure had Kenny George’s feet, would she be able

to maintain her balance if she did nt angle her legs backward, but keptthem vertical?

Figure 1.1: Problem 6

estimateinstance ofem . M

• •

location if herlegs were vertical

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a) As she bends the top of her body to the right las seen

in the photo ) , she must extend some mass to the left, to keep her cm above her feet .

b) Go ahead !

C) size = 3.1 - 24 => 1 C inches ) =

siZ}+24_ = 265242=16.7

Estimating from the photo,

it's reasonable to say " yes

"

shecould maintain balance with legs vertically oriented

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7 (a) In horsepower, what is the power expended by a 65-W lightbulb?

(See Appendix ?? for conversion factors.) (b) How many 65-W bulbs does it take, to expend as much power as a 0.5-hp lawnmower?

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8 In physics, Hooke’s Law describes the force F exerted by a spring when

it is stretched a distance x Force is measured in Newtons (N) anddistance in meters (m) For some spring with “spring constant” k =

10 N/m, which of the following formulae are definitely wrong, basedsolely on units considerations?

ok ? Nt F- . m2 × NO . definitely

g) F=k5x ok ? NEIMTM X No.

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9 As we discuss in the next chapter, the acceleration of a runner is sured in ft/sec2 Below are some formulae for the distance x the runnergets in some time t Based solely on units, which of them are definitelywrong?

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10 What might be a reasonable estimate for the number of strides anOlympic athlete takes in the 100-m dash?

=) # strides - lPm± = 100 strides

( somewhere in this range )

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11 In the horizontal direction, about how far is the diver’s center of massfrom her feet, in figure ???/

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12 a) In mph, how fast does the typical marathon runner run?

b) In mph, what is the typical speed for a fastball pitch in the majorleagues?

c) About how far can a college track athlete run in one minute?

a) a good ( not professional ) time ~ z hr

found online or whatever )

up with something reasonable .

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13 How many American football fields (ignore the endzones), laid end, make a mile?

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14 Europeans always tell their height in centimeters What is yours,

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15 Estimate the number of times a basketball is dribbled (i.e hits thefloor while being dribbled) during one 12-minute quarter of an NBAgame Describe how you arrived at your estimate.

There are several aspects which lead to a variety of

answers .

Most common student answer :

when dribbled , ball strikes the ground ~ once /sec

# bounces = bsae¥r 12 min × 920k¥ = 720

A bit belter : when dribbled , it is more like once every

je × 12 minx# = 360

Better yet : Ball isn't being dribbled the entire time

( also passed , shot, held . ) , but only say

be as low as zt . 360 = 120

=> allow a large acceptable range : 120 - 760

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16 In one variant of rugby (rugby union), when the ball goes out of bounds(“out of touch” in rugby terms), the ball is thrown in in what is known

as a line-out This is more or less equivalent to a throw-in, in soccer

In a line-out, teams can lift players into the air to help them interceptthe ball

(In rugby league, the other variant, line-outs are not used Instead,when the ball goes out of touch, a scrum– one of those giant huddle-looking things with both teams pushing against each other– is heldnear the spot that the ball left the field.)

In figure 1.2, Leinster (blue uniforms) have captured the ball on a out

line-a) Where is the center-of-mass of the three-person configurationb) The player on the left appears to be bearing most of the weight ofhis teammate If the player on the ground to the right would suddenlyvanish, how would the center of mass of the remaining two (takentogether) di↵er from that of the three-player combination?

c) Again, if the player on the ground to the right would suddenly vanish,could the remaining two players maintain their pose without topplingover? (Strength is not the issue– assume the players are infinitelystrong.) Explain your answer

d) Now look at figure 1.3 Assume that the athletes are infinitelystrong If the cheerleader on the right would suddenly vanish, couldthe remaining two maintain their pose without toppling over? Explainyour answer

a) am is below the lifted player ~ midway between lifters

the players would move up and to the left

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bon -d&\ approx $k of c inposition continued next pageon

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Figure 1.2: Problem 16 29 March 2014; Devin Toner, Leinster, and PaulO’Connell Munster, contest a lineout Celtic League 2013/14, Round 18, Le-inster v Munster, Aviva Stadium, Lansdowne Road, Dublin Picture credit:

Brendan Moran / SPORTSFILE

c) even if the players were INFINITELY STRONG

if the right player vanished , because the system

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two cheerleaders were very strong , they could hold that

pose even if the woman on the right walked away.

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17 a) In figure ??, the drum major extends his hand with the baton as farforward as possible Is that important for his balance?

b) Would this part of the routine be easier with a heavy baton, or alight one?

c) Would this maneuver look more dramatic with his hat on (as shown)

or o↵? (This is an opinion.)d) Would this maneuver be more difficult with his hat on or o↵? (This

to extend more mass behind

his base of support

it easier to extend one's body backward while keeping

one 's cm above base of support

c) my opinion : it looks better with the hat on

d) fact : the hat makes it more diﬃcult .

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18 Acceleration a is measured in m/s2, and speed v in m/s If Z = v/a,then is Z a time, a distance, a speed, an acceleration, or somethingelse?

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