Does a car speedometer measur a(4 3sp)qw-yt lj7izq4ptj:we speed, velocity, or both?

Can an object have a varying spee3u z8r9b onwr3d if its velocity is constant? If yes, give examprr zun8w 33o9bles.

When an object moves with constan7a4c9oc0 z izwj kaht(48 dpbn )gz7t-t velocity, does its average velocity during any time interval differ from its instantaneous vel)cadtg7 (kw cazi- 4nbh8479 0jpzz otocity at any instant?

In drag racing, is it possit5felr scv, x8o)y --qble for the car with the greatest speed crossing the finish line to-c5 t8y-,ve)f sloxq r lose the race? Explain.

If one object has a greater speed than a secondns1tso vxgt201w0x1:7 ul;+;b rl5 ns l jiyju object, does the first necessarily have a greater acceleration? Explain, using s l xil0ngrlwust1 jon5 1:v ts7+x2 yu;1j0;bexamples.

Compare the acceleration of a motorcy,4urso bgm ,1zcle that accelerates from 80km/h to 90km/h with the acceleration of a bico1b,4 gs,uzrm ycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velo:ltsotv c;ky(; .)h1p gm s;jrcity and a southward acceleration? Explain.

Can the velocity of an object be neyk2ga9u hojeq3 0sj/8 gative when its acceleration is positive? What abouejyhso3au0j g9 /2 kq8t vice versa?

Give an example where both the velocity and acceleration are negatbjz(-ils6n1ob 3 ti2 hive.

Two cars emerge side by side from a tunnel. Car A is travel3ht4u q-pkg) h 9wam.xing 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 outp4qa9 mxhthuw) g3.-k of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If so, pen8;)eodt t*give an example. If not, ex)eto*n ptd8; eplain.

A baseball player hits a foul ball straight up into the a bo179wpk 2nqk/e6pyavk8j+ fir. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will t wyo98qv7jpe+ nk21 kpk6bf /ahe ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its accelehcn,( j 1sq,vnration due to gravity — does it increase, decrease, or stay thn hns,j,vq(1c e same?

How would you estimate the maximum height you could throw a ball vertrv+h f6vm,wff),9 bxbically upward? How would you esff9b) wvhvb,,6f xrm+ timate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed of The y48tezsp-uosmt l5 23n 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 entire trip from A to C 80km/h ? Explain why or why2yez3musp85 t-l 4to s not.

In a lecture demonstration, a 3.0-m-long vertical strinqx w1t7*pec i xs(.i(mg with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecq mw*1i tx(e(xicp.s7ture 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 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: a rjhm9 6u:cz;f orml oqc./b ,z+ock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the +moq; lzoucrjh,c9f:bz. 6m/ way, a dish resting on a table?

An object that is thrown vertically upward will re:ygw9rm 03s qpz(ft 17d2midrturn 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? [Hint: The acceler:3qy mzdm7d0gf t19rr p 2isw(ation due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acce5af ,sx udyszy :ur8nqt+ k.)5leration at the same time? Give exa 8.y : usxfuy dq5sa5rtz+,k)nmples.

Can an object have zero accbkz5 f0pr 1rm3eleration and nonzero velocity at the same time? Give examplrbf pm5k1z30 res.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hiz(u*rh-:* n5m / ct zb ylk;tsd*hxyq0nt: First try to duplicate the motion plotted by walking or movinzh: sz yhlm/rk;u* cy* *(5-tbdq0txng your hand.]

Describe in words the motion of the obj3 rladpqk ;( si*4s9vvect graphed in Fig. 2–29.

  What must be your car’s average speed c)+1 5yfio uf0t.akbq1j*gdd in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15yoahf egk )4bn:kjpvm32zc x7 0, c1v6 km?    h

  If you are driving along a straight road and you look to the side *m5 dbpdh l0i9zlk1 gyx wrr1i(j:au x4;ko:8for 2.0 s, how far do you travel during tl gpxa0;5xo9*khr :l mbz d14wj8kr i1y u:d(ihis inattentive period?    m

  Convert 35 mi/h to d3e)y; d:t ce*,h; xt ufah+ne
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fr m)b1as78g(lpt 4vbtj3 hhi xy): sfc(om $x_1$ = 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 steadsh-.ucg* j0/8bqkisk o0 o,keily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 oghi s ,b-0 /ku8ks0.ojkec* qminutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every p -klt6p z69xvfive seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentiapp9x-6lv zt 6klly 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-mile track in a total time +zq)t um*z1)r seclfgupj,3, of 12.5 min. Calculat, *je 1)q z) um+lt,r3sfgzcupe
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m awawc j;qbvij*02p8j/f:(cf vdhy in 14.0 s. It then turns abruptly and gallops halfway j;wvff(hi80b *jc2dq/ : cj pvback 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 ot cb2pa/;q8rjb her 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 b 8c;p2jbarq/reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How lo( lvck+8 3 x,saqtvo5k(noqg g6u;*ewng will it take the car to reach the ntv qg gx5w*koqs83+c oa 6(uvl(k;,etruck?    s

  An airplane travels 3100 km at a speed of 790ukpj3)cpy o(rj ii3 pcln:4d2 83o n3c km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 km.o33 ndijjp 2uy(3r43:n )c pc kp8coil
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 rg/1, cylg 5v lcjof:l.ound-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 55 km/h g:l.c1j/c, ly5lvofg .    km/h

  A bowling ball traveling with cons;ymllv/+1 mehq g+-efr t6 ;b hu.pyp)tant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of t+ pvb;lquy;heepg6rm -fhy. m+/)t 1l he 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 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.cv; zf:ak-jq*i q4 ba-fe4)c p2 s. What is its average acceleec j-k*-ia4:cv bzp aq 4;fqf)ration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s (r(*kjziol 9c2osl5jin 1.35 s. What is her accelerationijs9l5*cjool k2 ((rz
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capablzpsh0( c f0if +pl.xd+ews(.ne of an acceleration of abou 0s0lnz .p(xdff +.scwe+hpi(t $1.6 m/s^2$ 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 ,yju /5wrf cl*(pfk ),ymy*vs it then brakes and comes to a stop in 4.uk*,j *y (syfrf)l y/5,m cvwp0 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 f((tw :4pj avsqrom rest 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 of tiwjts(qv 4a(:pme. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceleration? H. 7se6p ;9nj-caw abns0vocl- ow far did it travel in this time? p-wanbvec7 l9 0o6;snsj .a-c Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23qcf z)jq) 84bkp(xeeiqpl c0hh cf86,gr 82 0j m/s to rest in a distance of 85 m. What was its acceleration, assumed constanqqhc088kpq pel)gifx),h(426 0j er fczcjb8t?    $m/s^2$

  A light plane must reach a speed of 33 m/s for t*ykvuwkv-j6y +dx4 k- akeoff. How long a runway is needed if the (constant) v uwx*v6k-yd-4 jkk+ yacceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed (oflo9qfp/f 8s *n about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this spr8o9 *nsf/qfl pinter, and 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 12.0 m/s to rest in 6.00 s. :2mop jr r-jf(go562,axmre3t h na9j nn9 l1vHow far di3,1pote:r(ran2nj oj 9- g ah2j9vn5flm6mrx d it travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 ntkvn(,y*mnqj c ;0)fm long on the highway. Assuming a decelerayn0)n q,kt j*f;v c(nmtion 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 compc w vurc.9 . sspz2bki97)katcrw34d4resses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? 37.kt w4svckucsw) r9bcad2i9. rzp4 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 for a car with an i s:,/s;r qxc1) zcuilznitial speed of 95 km/h and hum1;z)uqsrl cs cz:x /i,an 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 stoppinqkd8vs ( s.g4epxl0l7 g 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 h,mb0uy6 b1e vf:xl5tr ighway. The car’s driver looks for av m5ly1b ,f:txr 0b6eun opportunity to pass, guessing that his 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 co+:e vnr +/7nyel p:ficmplete the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The run : : eli7cenfprv/+y+nner 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 km/h approaches an icg;u (x-qc;m vdy;t9j-ib4tt 8,aufz ntersection 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 befoc;-i- tt;9 tbq8 4c(m jg ,avfxyzu;dure the 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. It hits the grlk 72l4syz1rh9qu ogcx 18 0iklaf-7xound below after 3.25 s. How high is 184h7c- 9 qkxy g r1kzox2u0a fsllli7the cliff?    m

  If a car rolls gently8 vmm yn7pn*6x ($v_0\,=\,0$) 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 22 mf 3yjf :,)kag+g*1l3uk ovnoe/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 throwin trz5 ,xqu d1z(y*gec,g it vertically upward. With what speed did he throw it, and what height did it *q,uzct 5r zed1 x,y(greach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw 3muaa2 6 yyvta4 shw57graphs of (a) its speed and (b) the dista 4aut7yy6aa3s5 vwhm2nce it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.2l cc7 d8rwmo9, sx:d:h0 m/s. At a height of 125 m above the Earth, a package is droppedd c79s8 r: loxw:c,hdm from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled syexqol+n 5 *a.0vsy -during eaqexo a*sy.0 y5n +-slvch successive 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, ljqcmoylwl,d(agq).6 s57 o.5 v-qjhshow (algebraically) that a ball thrown vertically upward with a s. gmqs)owlyqj lqj l7a.,dv65o(ch-5peed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 13a2mc f n.r;nqay*oc18.0 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 apple in Fig. 2–18 (or number/(kj3.9gq3 l bl ja4pukxsz- r of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two aulr 9bkljjx-p( . k3zsga43/qpple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2–32)ebs+ef7. unm9 il+ u*w. From what height above the top oslnw +e7+9 .*muib feuf the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of i g :lfg)ug v(*:db3coyt striking the ocean is heard 3.2 s late:3) *:(ugdyfgobcglv r. 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 waterea 27q pt(dsl9 erp:ll 8zqg7*. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When yout 9(7 l*dqpsgqleeap72lz 8:r 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 the nozzle?    m/s

  A stone is thrown vertically u bvfqjy5q*3 h2qjf;; apward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (F 2ha;3* bqfq5q;fvj jyig. 2–34).
(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 window 28 m above the street wivc,ffr) 95)i nnl2z gsth a vertical speed of 13 m/s If the ball was 5g9rz, v2)ffcnnsl)i 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 t,7 u ql 9y-c: x6ss3jep4hnfzyime. (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) When was the magnitude ozpsl6fe3-ny uh9 4c7js,qx :yf the acceleration greatest?

  The position of a rabbit along a straight tunnel as a fuvhrz2hsr :s n3t,:k) du6b1yunction of time is plotted in Fig. 2–28. What is its instantaneous velocity d h2tb s:, s:kunu6 zr1y)3hrv
(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 show/,47ew o2rj, mdtdtx.b b(omon in the velocity–time graph of Fig. 2–35. (The short flat spots/ ewbj(, 4tobtm x2od7odr.,m 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 (Fig. 2–3w w;- o2v;okbo 4lvh3o5) when i4owob3v hlk;o ;-v 2owt 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 distance thzx u+d3far7c3bs( d i1e object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as 0fx s.r,ctz*h a function of time is givenc shr.0*,fxtz by Fig. 2–28.

Figure 2–36 is a position vers31tlzff(nos(n + urmktq6 3 9jus 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 the positive or nega n jr(fz6 ou tm1sf3(k+qtn93ltive 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 ne +s9(naq a+xvht. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37.xa a(9h ++qsnv
(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 on the Moon is about one-sixth what sdmsc:g*1a47x-ycv w it is on Earth. 7*a:sd v c4gcx ysm-w1If 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 properkzka;f qc54 8rly constrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if t 58fr4a; qzkkche 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 his pursuersj r:mig+s 3 i/.en7chw are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he me.i7jn wm:+/e scgrh3iasures 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 when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer testedn6 q ogr+8i08xem+vs8 ooyh+ d its cars for front-end collisions by hauling them up on a crane and dropping them from a ceigeq8mroos+ov h d +88ny+06 xrtain 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 travelshvy) ippgy+4 -1(.e xtbd yet, about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins unifory15q)hah1lbe 4oext) i8) uvxm 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. What will bet )1154)) ievexblhhxyuqo a8 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 in*mxsojqqy wq+u4 (at+,8jd m)to a deep pool. The person’s downward motion stops 2.au( q tw8,)+odxyq *m4jq+mjs0 m below the surface 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, d 5w.5+tx(wzq*rkr qqitl5 n transit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it 5rkw,x5t q5+it( zq.w*nqlrdtakes 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 wh(bgp 7y.pma e4en 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 perform evasive action, at what minimum height must it spot the pelican to escapebag p(7p em4.y? 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 theprbc:2 oudp:h-ikv 08 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 bip2p0c :: 8hk-orduvis, 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 1-tid x3i) yzhhop on a freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest andd3iz xyit1 h)- 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 buildd *x*hln3upm02mns9 cing. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a spmx*n*c p d 9snuhm2l03eed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the cous).pz eyro ko e. +.h:4eevce0rse of a time trial lasting tvooher pekc . .0e4yz)s:ee +.en 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 move9vilrbq 9e3r 9s at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average accelerationl3 rrq e9v99bi (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child c 0.sdteda -ep.an bounce up one-and-a-half times higher than the se sd.dt.e -pe0acond child. The 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 s5 28cz)f fqgx1.10-km-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 are tra)25cfszx fgq8veling 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 with a speed of 44 m/s In15d tf9v3af1bpqxk)ta+xh 1c 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 accelerationqff1+c9 b 5t1txh3vkp1)d axa of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with a;or fox9q (kk8n 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. 2–42. Each intersection hasnms5 j+ty+h-arrgfd* : d:sot32tr ; p 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 intersection, all the lights turn green. The lights ar+sr* ;rd3rm +ta - y5p:s gjd:totn2hfe 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, p+gkf/ l73jgaml fd3zq9*:n wxassed by a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant accewx97 zlgd3*g3lmjfa:qk nf /+leration.
(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 a building; 2.00 s afpb/ iv)grb+8a xjmu/*ter that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at8xrbmjg*a+ uib)p /v/ 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 )l koi79ef-*sui*m d *y /momhtime. The first stone is thrown with an initial velocity of 11.0 m/s from a 12t-io9*i umed/*oh flk)y m*m7 sh-floor balcony of a building and hits 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 resistafyahyh5 /dwc5bg5,*y0wg 9xm1o3qf t nce, how long would it take a free-falling parachutist to fall from a plane at 3200 3cy 0* w/9qwh 5xfgfbay oght55my 1d,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 burgers through a grill+vw / 6 6ya:;vujsq.jpbegk.-cjd* zc ing 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 spaced 15 cm apart, what is the rate of burger production (in burdcv/v: z*y p ;js j eq+-jwb..ku66gcagers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball verticak k2u80 y.4im+glhfz 2p bg-m -ogqgb,lly at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball m zgg20bkb4 oyiuk m -.8-,ghq2+gpfl go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff29x ;hbmku26w lwx:cb 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 belowl2k6 h9 uxbc2m:wxwb;. 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 friend threw the ball?    m/s

  Two students are asked to find the height of a particular building usia g 9oh)vf,r6hng 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 fal6vhhgo r,a9)fl. 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 vs. th0zovmuitdq 5y0(wjr /c1s ot 4(+x2zime graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the 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 averagzvri+( 1qtosc5wm(zxhdt42o0 / y0jue velocity?