Does a car speedometer measure flutz95yf.eauan 0++vp e )j nzj(.p.speed, velocity, or both?

Can an object have a varying speed if its velvkeg 8u5du-09drdkt9 x)c9fgocity is constant? If yes, give examplesv0g9 c-du8 drde)k x kf99u5tg.

When an object moves with constant velocity, does its average velou35v aok m,bf zz6(bv1ytlg 9/city during any time interval differ from its instantaneous velocity at an bb1t9kf3y(vu/ zmz,avo6lg 5y instant?

In drag racing, is it possible for the car wiamw:nd 3d4- obth the greatest speed crossing the finish n4wabd3md -o :line to lose the race? Explain.

If one object has a greater speed uu r,jfc .6ap z1,ms3othan a second object, does the first necessari1omrfp,ja3s6 .cuz, uly have a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90 f6u4hfolun1n*r), aesth5c4km/h with the accele,ou era h5l* c6suh4fn41)t nfration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity arb3f4jo 9vl: pnd a southward acceleration? Explain.

Can the velocity of an object be negative when its p1f .k mtjwix p1 3m7v(axe+y9acceleration is positive? What about vicwf7xej( 9p+1ipxtm .m1akyv 3e versa?

Give an example where (yk6n, (x l :)fijajwgboth the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Caqn6a 61hzd5vmr A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of d6va1nq6 mzh5the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration dwbgdsny+avkpw+*d m;l0(/h 8 ecreases? If so, give an example.yh p */vddw+b;+m ngklwsa8(0 If not, explain.

A baseball player hits a foul ball straight up inex (z+;7 ljkbmgk / 2dli10tbpto 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 +k2x(li;z1bbt7 e pgm/kjl0d the catcher catches it?

As a freely falling object speeds up, what is happening to its ac ,fje6qa -t vw77yuzu6n(ti:l celeration due to gravity — does it incr tze6 liv6 un7w:yjq-7af( u,tease, decrease, or stay the same?

How would you estimate the maximum height you could throw a balladfofjr1 4 m;( vertically upward? How would you estimfm1j4 f(aor; date the maximum speed you could give it?

You travel from point A to5pcr 5zu2ael2 point B in a car moving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant sprl 5p52za2ue ceed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical strin: or2n 4vszgewm-l2a5g with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, 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 decrea l 5nse-4rwv:zog2 2mase 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: a rock falling 1 6gu, rw+e xb/7xjjzlfrom a cliff, an elevator moving from the second floor to the fifth floor majjx6ul1 w+z7r/xg b,e king stops along the way, a dish resting on a table?

An object that is thrown vertically upward will rgw3vui w9 o8nq 36y,kketurn to its original position with the 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? g6u3vyki,wqwk38o n9 [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero accelerae9vkc37;css :o-sc hb tion at the same time? Give examples sbce9vhckco:7 ;s- 3s.

Can an object have zero acceleration and nonzer c1aq exq:7dw3o velocity at the same time? Give exampleq7axqc: d e1w3s.

Describe in words the motion plotted in Fig. 2–28 in c(em vts5;16f xlb9qb terms of v, a, etc. [Hint: First try to duplicate the motion pbcme s qlx;tv95 f(6b1lotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Filyr3c 7xp*wgu1m9s7 m les4sbp4i4n4g. 2–29.

  What must be your car’s average speed in order to b(y etg9au4l8 travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km?h: h(8lu t.dux    h

  If you are driving along a straight road and ynkzxot+g34 +f ou look to the side for 2.0 s, how far do you travel during this inattentive p+fz 3gktx on+4eriod?    m

  Convert 35 mi/h to uh0i*na4k 5s).qry bx/qlrqp1e n s 1,
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from ;dzor//rye67 e5/;o ojyw fu a$x_1$ = 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 razi7 f9zb epn225+kg:/y bll at 95 km/h for 130 km. It then begins to rain 2a z + lgyn257bpb9/riklezf:and you slow to 65 km/h You arrive home after driving 3 hours and 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, every6pu earwws2pc6d1mmg- 44qe)p t )o b 8.tunb2 five seconds between a lightning flash and the following thunder g e8p61 4pn2)4osm2cq. we m atb-d )rubw6putgives 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 compl.nk4;2s ldbddmczr mz86 a()kete laps around a quarter-mile track in a total time of 12.5 mins8acn(rd ;m4 d)mlzd b2.kz6k. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, movingxth5q uem kac 0z1.oqw.u-; 0f 116 m away in 14w5xm -qezq0oa. uh 0.u;cfk 1t.0 s. It then turns abruptly and gallops halfway 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 approach each other on parallel trb/ bt07;7mp haywa;3b:crz ibacks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, hoh;a7pcat /mbr7ibb; z:y 0 wb3w long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck travelinhk5a0 gd8okc2 g How long will it take t0ahd5c kg82 kohe car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encou.rwi3tt w 2sn5nters a tailwi53w tr 2sni.wtnd that boosts its speed to 990 km/h for the next 2800 km.
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 vel, o - cz3lknr+1c9jqleocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 9+er-qcl1 lj3kn, czo 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at the end of05+ssm xn myn: a bowling 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 balyns5m:s+nm 0 xl? The speed of sound is 340 m/s.    m/s

  A sports car acceleratef.ti h+- f8i; v6)c:hckrgtmcs from rest to 95 km/h in 6.2 s. What is its average acceleration hc-v+ ttrh :. ; kfm6if8cc)giin $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35sdhu 2u6 p3i(z s. What is her acceleration i6pu(h2 sz3du
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an accet5w sjgz0i 2hzff4,.xleration of abouts .gf whz0 fi,2t4xzj5 $1.6 m/s^2$ 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 constant speed travels 110 m in 5.0 s. If cs5k -ux yert6.md*8 xit then brakes and comt8y u*msr-ced5xkx .6 es to a stop in 4.0 s, what 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, which starts from rest -fyrk-wuj2n5 at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function ofk-uj y5 nw-r2f time. Display each in a Table and on a graph.

  A car accelerates from 13 m/stqd7a0ho :q i6-g zq6y+wa o-p to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constant acc o -q:pq-aqt6g aohz6yd7iw 0+eleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85.g0f+ jlog v;a m. What was its acceleration, assumed constant.;0gfg+o j avl?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runwayh f2ip *7w-o0vwd b0fj is needed if the (constant) accelerationvh* p20wwbjd7 f0-i of is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to e)l, h q*fi2mc+iier j-ssentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and * rf,2qmh) +ilcj-iie how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 191 u q :dfvn*pr9ustuthg mm4p1cui1 :i8*kv)2.0 m/s to rest in 6.00 s. How far did it tr*19gt8hu1cs:uf1drt4m)9 viu :v pmp nqku*iavel in that time?    m

  In coming to a stop, a carf q/w 0m ),*d,cyj5*hwivm eec leaves skid marks 92 m long on the highway. Assuming e/m5chf,ceiw *) jydv0 m *q,wa deceleration 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 trpd,o q7k8 m0oy w(fpr3ee. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the ao p0 (kq8rwdy,fomp73nswer 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 for a car with an i cu:l- j9ih/ltnitial speed of 95 km/h and h h-cul:itj/ l9uman reaction time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopp. d0s0+8sut; s cx:btboa2xgling 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 going 25 m/s on the highway. The car’s driver looks fj0gi nf-mo 5gj) km76eor an opportunity to pass, guessing that his car can acce)6o 5 jmki7mej0-ggn flerate 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 complete the 10,000-m run in less than 30.0 min. Aft7f o x; sldbqi:dj32*ger exactly 27.0 min, there a7flg* 2 dbs:dx;io 3jqre 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 her car at 45 k0r ,rys14ft-cncsu/ nm/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/ryt1n nc rs-04,cfsu light turns red? The intersection is 15 m wide. 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 the top of a cliff)4rg *b d(svzk. It hits the ground below after 3.25 s.)g zrd s4(kvb* How high is the cliff?    m

  If a car rolls gently (ioi s52c. 6hg*rps5v r$v_0\,=\,0$) 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 straight up into the air with a speed of (p ;ka 0,zpqkg22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it ver4 b; +x2ab0.ut.ycwbtua / otftically upward. With what speed did he throw it, and what height dibxta/ b+ faoy 2.cbt0uw.;4tud it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the inqgp -flap0 ;4rfluence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as af-q 4plapr; g0 function 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 height oqnnog 8-sgnq6y97:hufd8) smf 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? [Hint: The package’s initial sg6msqqfn7:h8o9y us )n-nd 8g peed equals the helicopter’s.] t =__ s

For an object falling freely .hv dxejrb5 r5/)tny ko.x-a 9 pmu9d8from rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5,dd/5bt5..xp 9a)jx r 9n -8kehory uvm etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraicalfwnhr ) ,tya, :dm3qc1ly) that a ball thrown vertically upward wqmwft3, an )chr:y1 ,dith 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 upwarqhahns) p y,pciv7bim y4: ,.1os qs:.d 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 akzh*i 81 y95dc)mxg pppple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear o*yp c)dmzik1 gx h5p89nes at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fivm9b+d b+ 0)eygc2osbg. 2–32). From what height abovebo+2g c0emdsvb)y + b9 the top of the window did the stone fall?    m

  A rock is dropped from a sea cc.ik1xtk z3 1xliff, and the sound of it striking the ocean is heard 3.2 s later. If the speed of so t.3cxx11kzi kund is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle u.m-i 6ac ;i+umj/hnnfor a hard stream of water. You 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 ground next to you for another 2.0 s. What is the water speed as it leaves t;a/6nuni.j cm mh+i -uhe nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the erx :.xt,ze; hvwajcw xw(6xvx153(g mdge of a cliff 70.0 m high (Fig. 2–3m xxr.6(t5xvz,w( ww;x jc:egx13 vh a4).
(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 ppde/ rg4 wd20a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown frp 0/weddr pg24om 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 a vm8p lo73de4ts a function of time. (a) At what time was its velocity greatest? (b) During 8telp4m od37vwhat periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel asle+ p/pka* hk( a function of time is plotted in Fig. 2–28. What is its instanehapl+k/p k(*taneous velocity
(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 automobile can accelerate approximately as shown inlc r:;;hm qkqy8f)w+d the velocity–time graph ofk8 +ldy ;qrhwq)mf ;c: 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 averagec5 gsfk i6q 4n+q5f;pi acceleration of the car in the previous Problem (Fig. 2–35) when ni 4fg5qs 65p +cki;fqit is in
(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 dis u lo*q/w;j( ,4r; l1attv+ pvn5uukistance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object)2h +km v+yoej whose displacement as a function of time is given b +jom) e+hy2kvy Fig. 2–28.

Figure 2–36 is a position versus time graph for the8 9,ppz/abmm w 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)mb9a/mz8pp,w Is the object moving in the 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 firefighter’s safety n 3lr(( ukf 1nttpd:1siet. The survivor s t1sp(run:(i f kt1d3ltretches the net 1.0 m before coming to rest, Fig. 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 tocr gqugvo3r:d ;2e l.* gravity on the Moon is about one-sixth what it is on Earth. If2d:e q*r;.gvcro g 3ul an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained bydyj)yt-a *k0 u an over-the-shoulder seat belt has a good chance of surviving a car collision k*0 )uy -tyjdaif the deceleration 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 above the road below, and hi3nl)nc -ko ,tps 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 away the truck should be w,lot kn3c- pn)hen 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 collisions by haqg1 ;b :ro)ig;.yt mrj6r rmi:uling them up on a crane and dropping them from a 1 )m rmq::ry;grgo tjirb6;i.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 abouth ari2i3zaz0gtmqp k t0 588n; $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins unifovu)v m// )16t*, qwm:p1gnjytbxnoewrm acceleration from rest. The front of the 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. ) 6w v:g1ywtoxp equ/ ,/1tmvnj*bm)nWhat will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface inll .r)y:mtpl 2to a deep pool. The person’s downward motion stops 2.0 m below the surface lrly2p.:t l m)of the water. 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 ni l5 nq6og87 rgmgcn1.ecessary to balance the average speed of a train against the distance between r7qmg gnnc log 8.5i16stops. The more stops there are, the slower the train’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 ihq;*hivxa ;.xnw p3iqoz 0,,5 mf(pt down when diving for fish. 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 perfo3ha5 w mn0qi, o;ipqhft, * ivxz.(x;prm evasive action, at 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 65 e/xzgd 7jbe, hw xk447jr:tlnm(lpwhich a golfer strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing 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 partzwlj:x6nrb4 7l7kje,t gh4m d(x5/epicular 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 traveling at a constant sjjly 3kpr5a6.z5 ryu; peed of 6.0 m/s Just as an empty box cjay6l5yjr 5k pz.3;urar passes him, the fugitive starts 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 3 *9 ov6l dkwxy1um 2nnv0v.dmof a high building. A second stone is dropped 1.2 duvd9w*xmv1.nlomv3 06 nyk50 s later. How far apart are the stones 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 course o.3g i:+ :qbdxh dye/ dozetfo:q t)p,:)qqn/kf a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h .q:/.n+ybd k3 h q:ptg/o t)e)fdz x:qqed,:io 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 moves at 18 km/h s3ud- mpn61i j. At th31jp m-n 6iduse bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first c*de+7scyu v7y, /okxdhild can bounce up one-and-a-half times higher than the second child. Theexk d*+ycous77/ vy, d initial speed up of the second child 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-km-long train trzn/l / aznt/yxb ni;bg auz:0.z( 4q;waveling in the same direction on a track parallel ni(.bzztg b4//na/l:qyzxw z0a ; n;uto 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 are 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 wd+h rvcm -v h)e-mo-.hith 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–vhm+e horhmd-vc - -.)41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, ofgg; 3m3d qbjx+ nml9tj5yxia91:y2with 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 shown in Fig.dz dce3d.1zl 5 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 the first in5zeldcd 3.d1z tersection, 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, passed by a speeder traveling at aob8k s0 1):ncywcsjy : constant 120 km/h takes off in hot pur0cy :sc)8:jo k1wbnsysuit. The police officer catches 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 roof of+ay :hvf8t9zc a building; 2.00 s after that, a second stone is thra9t+f zvyc 8:hown straight down with an initial speed of 25.0 m/s and 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 at the same tim*bqx7ykp2m90p3 7 x.luyo cwy e. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and bk op7clm*y2u qw7p 39x.xyy0hits the ground after 4.5 s. With what initial velocity should the second stone be thrown 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 tar;.e+to,rp/mp xmn )ld/ y(v eke a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she wilrxym npm+,l t);(v /ed eo.pr/l 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 sent9fq* 3 -*pq 2ju yrlh)k0yaxnd the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are sa)q0* ufxl*yrpy3 h-2 ntj9k qpaced 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 timg a2wz hw..zv18xr k 6y:q;feres faster than Joe can. How many tim2 zqa.;.6fzww1yx rv:eg hr 8kes higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a ut a wyu/+b(gv8iv r;9cliff while your friend stands on the ground below 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 throws it up to you, such that it just comes to rest in your hand. What is the speed with which your frie u vbr(g+; a9u8/vtiywnd threw the ball?    m/s

  Two students are askedid oba:p 93cd68zhl9 br/ jdj+ to 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 roo/zcipjhl+ddbd:b 9 6ra3o9j 8 f of the building and drop it off, timing its fall. One student reports 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 neqqvq ha,v:x6m s*6 e8sk6k)vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same v6xqqv:v 6 km6) eqahess kn8,*elocity? (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?