Does a car speedometer measure speed, velocity, orrwku4:5pm+ w cjne/yri, lg4* both?

Can an object have a v021k)b4zq*myhy ux h:yc zjg9arying speed if its velocity is constant? If yes, give examj9*y1k z: 2xyq0 )cg4hmyzbuhples.

When an object moves with constanp,a-g;ukhw 4 at velocity, does its average velocity during any time intervu,-h wp;ak a4gal differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crjcjs-vcp mml 7yl 0/ix sa,4,::8ku ryossing the finish line to lose the race? Explaicl/ m::,psj7cy-ml8s 4rkjvy iau, 0 xn.

If one object has a gypuj;zu. tl2o/- g.g i 5wgzo7reater speed than a second object, does the first necessarily have a greater acceleration? Explain, using exampleg2ug 7 jwoz.gp.yu5t/- ;zoils.

Compare the acceleration of a motorcycle that accelerates from 80xo)sp* o8quh,g0usul 0o 3mn ,km/h to 90km/h with the acceleration of a bicycle that accelera0oosuuhx ql,,s*8 u3o0nmg p)tes from rest to 10km/h in the same time.

Can an object have a northward velocity and a soutez o1s 7:;ealdhward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? Wapq wqft2xa 28n2z0 m6hat azp 2am6qn2xf8 0qwt2a bout vice versa?

Give an example where both the velocity and acceleratio,ohdzeyhd495 n are negative.

Two cars emerge side by side from a tunnel. Car A 56 kjxx97sq dkz1q*ywo)*zx0am z 9lvis traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 4mazy*k josx0w6zq )z5qk dl7 x9v x*910 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in 6o0fvbok4b coo4 :dz+speed as its acceleration decreases? If so, give an example. Ifvooz 6bc0 d+ ok44:fbo not, explain.

A baseball player hits a foul ball str0,w3 r;r lwef wgl98qcaight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catc re,wfc3qllw9w rg8;0 her catches it?

As a freely falling object speeds up, what is happening to its acceleration duiw m sw.cgi z..*-rh6oe to gravity — does it increase, decrease, or m*.rg.zowc 6i. hisw- stay the same?

How would you estimate the maximum height you coulduq*fwch-th4;d.y y y( throw a ball vertically upward? How would you estimate the maxiyywu; -t. cdhq(yf4 *hmum speed you could give it?

You travel from point A to point B in a +h* avzsfct;8jad x8d t0c2ja5fsc/8car moving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the ez cd2/8 ; 85cac+ta*fsfvj t dj0axsh8ntire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical strin un cy:d9(26ziolsb4ug with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin platdl26 ob:scyni(u 49uz e, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: ax16ipm jvc+2;2 +po gpub9yz1ro5 tta rock falling from a cliff, an elevator moving from the second floor to the fifth floor t my+cpi vg;1 6zj2bx1 trp pu25+oa9omaking stops along the way, a dish resting on a table?

An object that is thrown verticallys hsy7 fy*+x lmxfgc3nu o(7); upward will return to its original position with ton3hfsy) x7 *fgu+;7s( yxc lmhe same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero vel sp3 kw;we wi fi6*)+-qtql0thocity and nonzero acceleration at the same time? Give i e-s*wl+6 h 3pwf;wk qt)qi0texamples.

Can an object have zero acceleration and nonzerod)a v km4yk+tedo:r04a: uq;j velocity at the same time? Give exampka mq0t)y: je4odv:;+4da rukles.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint,s,v *m- qif9)2.hnuiztzat j : First try to duplicate the motion plotted by walking or movi*fmuz .t,zsa)q-ijv, it 2h9 nng your hand.]

Describe in words the mo1tcggem+kvb e-1;f( rtion of the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.254lu -gqjv,5tk-q- mxwq-so;y h?    km/h

  A bird can fly 25 km/h How long does it take to fly vfw6*e2p*;5 amj xjrg15 km?    h

  If you are driving along a straight road an)ey (j60iu rn1e7wtvyd you look to the side for 2.0 s, how far do you travel during this inattentiv riw()yn617ut0 ey evje period?    m

  Convert 35 mi/h to 5nq(ry6o2qx98xp:u kg 1zdrv
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fromq irj6u*h vt8n 4ts nls17hq4 iza5s44 $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home from school steadily at 95 kmq ey1 :0n--6ebpix3cza1 ruvv/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours aenev1azcv -13x yurb q0-6:ip nd 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every fiveg(u69ds wlfh7: m/y/bw jtqiv5 b8+ lf seconds between a lightning flash and the st/+h8l7w /by jif9( dlwqb 65fvmg:ufollowing thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter roxx(. r25l+lk*dfqg-mile track in a total time of 12.5 min. Calculate fx*gl2l xd(5+. ror qk
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away fqh2zz3 g45nikkz nil, 21 kfu 7;a9eabrom its trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfw kazzn9gk2qa 5fehz1kl u7n4;2b3i ,iay back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approaff)aw*cdph 8:w)wz i6o 1gs6gch each other on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they rec1 w)s iagzg w:*d6f68f hpwo)ach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling 7 e1pojf h.q)f/0z pjn How long will it take the car to reach thezfn7j 01jhp/ oqfe.)p truck?    s

  An airplane travels 3100 km at a spepwi8x y2s +2ajed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 km.a+ys2 wj2px8i
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round-trip inf8oxzigad +yc a/ 3t q/8kq.u3y +mn0n which the outgoing 250 kmq3dng+.+ 0cu8iqt/ax z 3n mkay o8/yf is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at the end of a 6jknf,b9/u wc,z 4 h d,qk4gbmbowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 3z /4ub , hfkqn 6mb,jd4wgk,9c40 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its a5mn*ph7di wj:p58a ubverage acceler iwb5p8n5j:ah*7md up ation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from restdt0rdnny .5o ,zj9p5r to 10.0 m/s in 1.35 s. What is her acceleration 05n, r9nzdjpdro5 yt.
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particulaz5shd pme x+gf5x43 ;ar automobile is capable of an acceleration of abouf+dz5x ep;4msx35ha gt $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constm:45c(v*sgyxiw zl9 zn yc qg1 4-ru.iant speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, whc4m5iln c9xigzq *y :- gz.r1vw(4ysuat is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car,ih m:zi;x fl3-ryk+*ub6 yyb : which starts from rest at t = 0 and moves in a straight line, isbi6 -:i+; 3xyufb *:y lryhkmz given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/+i+yq-l6l2t fzsk dh/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume con2kl-s/t yl hd6z+if+q stant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s tla 7 *ue xcmp7pr4lh:g3 uv8g.o rest in a distance of 85 m. What was its acceleratiog7v.mp g3* lp 4 uhxc:ur8ela7n, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runwayi/uaashaq -pb:(r 4eoiip - s;k7g+t+ is needed if the (constant) accpii7 o-s/+-ihak buq4get:s ( +;rapaeleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to es/kxupid5 .g5dy wq f-6sentially top speed (of about 11.5 m/s) in the first 15.0 m of the racpk5 y d/dugi5xw6-q.fe. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformh nev-ujm0q3; (lwp sa0g9qt,ly from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that e9ns( q0v-u 0wlg ath,j;3qmptime?    m

  In coming to a stop, a car leaves skid ma wf:5ord9 jw/0lmq:rurks 92 m long on the highway. Assuming a deceleratow djr: mul/w9 rf:q50ion of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compres(o,a - g9zdy /wqsscre3 ntd3)y1+ boases and the driver comes,a9a( d oydz3ys)qt3- bo/cws+gn 1 re to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances b st wtp)uv(nh3nqoml u 9 r 1;)giyx641/,pjdfor a car with an initial speed of 95 km/h and human reaction time of 1.0 s, for ant4n t gp)h lbuop)ndim x1 69(/vs;uj3rq1 w,y acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation n ia7h4+o/eiyfor the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck :,yyuqjmmhbzfy9 . bf 419 .nlgoing 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that hjfzb ,y.u9 hym 4f.yblqmn9:1is car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to compleb b3p/y1:e;p ai bmgwtt 6he46te the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there ar;/:6ghmbe tbewp4yt3p 6aib1e still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her7v5+o,z54s ef thjcr tp6 mw(n car at 45 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m f,45c6zj r+(5 ev owsnht mpt7wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from imy ,9.iadmv;b:a/ r/khp/ntthe top of a cliff. It hits the ground below after 3.25 s. How high is t/9pk. hbn/tm , arv/:idayi;m he cliff?    m

  If a car rolls gentl b 230rkgm( -c ea,7vubewpflgt0+q3by ($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly strv z29lva7 ks)waight up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches avaw/y.2s-ef)6y v 8hjwoe o7p ball 3.0 s after throwing it vertically upward. With what speed did he throw it, and what heighp.-s6o/ aevhvo 2yej )7w8yf wt did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls jli*gthmyb:uu 9s/2j9)b p k1v 6rx x,under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a functium 9r,pj y 9x/1s uv 6j)bb*:klx2hitgon of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a heigks ,t xhcm43ulr6h(j,ht of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? 6jhmsxlc,u kr,h3 (t4[Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that th5vp 7o(;m2n+u zke wq y.lky6se distance traveled during each succek(zyp+my n 2lk7.w s ;euv65qossive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, sho.znda:8 o :zxhw (algebraically) that a ball thrown vertically upwardoz.a:hdx n8:z with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upway2j s9z ;cpge0rd with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the appla 9q6bf0jdtff * ;2icpe in Fig. 2–18 (or number of photoflashes per second). Assumef9bf qi6dt* a0p;jf2c the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travelk 0b/t;f ylc 7-6pkijr past a window 2.2 m tall (Fig. 2–32). From what height above the top of the -k l fy/7;p6tcb rjk0iwindow did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the obuu65lip *81l 9xytox cean is heard 3.2 il6yb5*8l uo19 p txuxs later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. Youjyqs.qo ;mr4iyroc)w*91 j i, point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the gro* wq,q josi. 1y)iycmjrr49;ound next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from n -g ui6ic-qlau3))pm the edge of a cliff 70.0 m high (Fig. 2–34). 3p)) 6gaqimuul- cn-i
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a windo:-z0tz ayi-g-u0db tqqe+f :sw 28 m above the street with a verticfgzut: a+d 0seqtb--0 q-yiz:al speed of 13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of jii9 2 keiem vb* m5ehxo8x49mp9pa,6time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) Wh9ee em8pv9xiio i ,p jx h9m2a6*54bkmen was the magnitude of the acceleration greatest?

  The position of a rabbit along a straighttfl )4bj(wn:d tunnel as a function of time is plotted in Fig. 2–28. What is its instantaneous velo4tld(n fjb w:)city
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

  In Fig. 2–28,
(a) during what time periods, if any, is the velocity constant? t =    s to t $\approx$    s
(b) At what time is the velocity greatest? t =    s
(c) At what time, if any, is the velocity zero? t =    s
(d) Does the object move in one direction or in both directions during the time shown?

  A certain type of automobileyk0 *9rmuhv)i4 uso 9a can accelerate approximately as shown in the velocity–time graph 9 ky)4ru0u*iohm av9sof Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problem*(lrn5d s jtu7 (Fig. 2–35) when it is 5j ul7r(d*s ntin
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveled dur5sowwww/7o2 5ocf op. ing
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the objrwy4b6y3lpk(6( jch vect whose displacement as a function of time is given by Fig. 2–6yp blwch( 3y4(jrvk6 28.

Figure 2–36 is a position versus .lze)9b5i g; poqx-yx time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in they9x 5bi -qolzg.e p;)x positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefightey q9d-q8yj zm w azxd;j(f fwh6174h1ur’s safety net. The survivor stretches the net 1.0 m before coming to rest, Figw f d7j -xy9(qhd;qwy1mzuf azh64j18. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity o pmq-w9y+8uf kn the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial98-k qp wyufm+ velocity?

  A person who is properly constrained by an over-thtd; u kad6+a7/j w8nzye-shoulder seat belt has a good chance of surviving a car collision if the decelerationwn+8y/u a6d;ja dk7z t does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m abo tv ea)t;cwyun; kw976ve the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles awayvu;wt);we7 na ykt9c6 the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end cojpq1b*j l2 o(sllisions by hauling themlj(b 1p qs2jo* up on a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels aboucs. d* y5cht6jt $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from rest. The front of thg. 64k5c(es olsx)iije train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–3sgs5( .k ci6li4o) ejx8.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface into a deeachd 9uxq6+yrgj.5t.es 1- lsat(z ,kffp, 8s p pool. The person’s downward motion stops 2.0 m below the surface of the wat, 1,as fzt. 9(lygx- cr.s+ sdpue5fja6qht8 ker. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessarg0s,vx cn 6idr/; dk-gy to balance the average speed of a train against the distance between stops. The more stops there are, the slower the tx0 vd/-kr s6gdn,c gi;rain’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fi*n q1sun-*wex sh. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, ats**1-neqn xuw what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so that tmmihw,; nl-a:pv ky(:he ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Acco(nipl, ; -y :mahvkwm:mplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train travelij0v:huzw( lq) ng at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive start h:q)0(v lzjuws from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A sp-i rcjzjm2.q9 0lb5eecond stone is dropped 1.50 s later. How far apart are the stone.jjm2p zr0e9 cq-li5 bs when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the courss eyb;;p v/6 r9mvvxx/g.jl( h vofn, v2n,om)e of a time trial lastinn(v),p;v lm, vveh6rv bgnxm 9x/o /yj2f.so;g ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he movesgg(yn5fug vqklt(2) dkokv8 1 8d*b1q at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average aclbkn g qv(ou*qy8(8t ddk)5 vg 112gkfceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two tramdu/x8 m48: wzeeety(aidj( b 2polines. The first child can bounce up one-and-a-half times higher than the second child. The initial speed up of the second childwz/x4 2db8i(teu(m8ad ee:jy is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-k1mvc/ l ui:/tnm-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train at uin:1cmvl// re traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball wit -m1hai yj;+slh5m*tqzf r /,vh a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during thm-htlhr+ja1;/ zif sm*5q ,vye throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, w- wb5ruhmusi 0f8 10izith an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern 5;;iutmo whv+j4 u7le7 hhe/c shown in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from ; 5howu4teluv7m/ 7 h hc+ej;ithe first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest n5/:y5lp5pr . jcxqmt, passed by a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catche5y/p m.t cxp5:qrj ln5s up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof7--svih ;g5cjll.u hj of a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and7uh5s cv-lg -jhli;. j the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up t8 aspy/0s/fsat the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be throw/ysft0s8 s /pan from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-fallu b0 jpizasr u u3s-1-fi1*nt5/qd)y zing parachutist toqurbt0ni*ssu 1p z/y z3aj5-dfi1)u- fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the b4 xragwb gfi;( 51q2rur/u8fj urgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.;8(/ajq f b1rru u5frigxg42 w5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe ca nsvcne0(;q-u n. How many times higher wilvc- 0nqu(ne;s l Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground beo7sr5 5hwh2evlow you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and thrh5v7 r5osw2 heows it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked 6 8 ;skdv b 4wkih.6ax8;dzcvjto find the height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student rh6v i8k jwax;; dcb8d. zks6v4eports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position v uqkl113e/ia g3l+)nahv5vd q s. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have t/vd ie1 l35g+nqlahqva)13 ku he same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?