Does a car speedometer measure speed, velocity, ore x35vm)q +pdp both?

Can an object have a varying speed if its0e)xgd; otnnxen5 x:4 velocity is constant? If yes, give examplee4 ):0nnt xxn;od5eg xs.

When an object moves with constant velocity, does its averagednro+nt 4/d3e velocity during any time intervat nd4edo3 +/rnl differ from its instantaneous velocity at any instant?

In drag racing, is it possiblemysr0if+4 56y* (n.m66f z xdt dtdeye for the car with the greatest speed crossing the fm6 dx*e5 tif0e+n mydr6s.zf (4d6y ytinish line to lose the race? Explain.

If one object has a greater speed than a sepgxvj6; pj2 v8-zgd gmb/) ii8cond object, does the first necessarily have a greater acceleration? Explain, using examp6miivjgpz d8gx; 8vb/j)p -2gles.

Compare the accelerat/ghe,npakcv1b:p 9 n9y tv:5w ion of a motorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from r,ab1 hnw e:5pyvknt9p9: /cvgest to 10km/h in the same time.

Can an object have a northward velocity anvc 13qhk hn*q9d a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is posit,;0httarc(; pc66yl-brsj i8ju ty h1ive? What about vic6jhyjartrc8,0ypc1t - ubs(l; i t; h6e versa?

Give an example where both the velocity and acceleratioxdh;(r d9u,q6vb uu) on are negative.

Two cars emerge side by side from a tunnel. Car A is travez.dewy*91 wioling 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 . Whozyiedww . 19*ich car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its accelb4;9zoi:x9h.n f znnw eration decreases? If so, give an example. If:w9znxnihb on9. f ;4z not, explain.

A baseball player hits a foul ballno, u* txgfsv)l72i 7c straight up into the air. It leaves the bat with ix v7)ctol*usn 7f2,ga speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happe-7kh-p ttavofznqm + 7mu4 jd7p3di;0ning to its acceleration due to gravity — does i3p 4n;+jfdvtq77 -0a kmditzm-upo7 ht increase, decrease, or stay the same?

How would you estimate the maximum3o)ll:w473 vqx-j qw7siyf cs height you could throw a ball vertically upward? How would you estimate the maximum speed you couqi7 j) yc :svl3xos wqfw4l-37ld give it?

You travel from point A to point b)l 2ly7)uoh lB 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 speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain uoh)l l)yb7 l2why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten boltsb6tlnxr 2v .(x0) hlxl tied to it at equal intervals is dropped from the ceiling of the lecture h6nlhx20)( v xb.xtlr lall. 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 *y 9q ndq/oko(x.7kbtizn(0iwwz 3)i is not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor makinxkb znn)i/* 0ii9k q(o7q tdwz.(ow3yg stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original positionejgka 2+xsv.dybv3 5jpp n:40 with the same speed as it had initially if air resistance 0syb2pg: +p5a.e 43v vxkjjnd 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 velocity and nonzero acceleration at the same time? G v3w5 rklc dr03e)4vluiver l5 lvc)u3kw4r3dev0 examples.

Can an object have zero acceleration and nonzero velocity at the same time? Gn1k px4+,zpf( zah p;give exagf(1zp z; hpkpn,+x 4amples.

Describe in words the motium4ke5y(rgbe *8 t ca,ij5vf9tlss-: on plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the mot8tlty m fb5k,5ug esj vi*-4s9 ar(e:cion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in F0s3fj lmd1i 9v rf .h:ii2s0x0kr7rnk ig. 2–29.

  What must be your car’s a+/ dkh2k)jvr iun g11dverage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h Howhsoz3yyf(vr (48 kebz) x5n4r long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side form.(qj /nhk w*h 2.0 s, how far do you travel during this inattentive per.kw/h h(mq*jniod?    m

  Convert 35 mi/h to .y )ri7d z76q,jyi(yarz:r xo
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fr n3-fyt9 sj in0q)q*vpt 9t7qhom $x_1$ = 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 km/h for 130 km. It then b /vji+wrg))gqegins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 minutr )ggj v+i)w/qes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seco )g u1(zk39gxiyka) sjnds between a lightning flash and the following thunder gives the distance to the flas( kjg)zg ksa )3uix91yh 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 ty *rnp s7iyu t.u8dk;3oqq.9laps around a quarter-mile track in a total time of 12tkdnsp 8qryt3 7 y.ui*uq.;o9.5 min. 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, moving 116 m away mcn t: x,(y1fm7b/kfgin 14.0 s. It then turns abruptly and gam/,tgkmx :fn f1 y(cb7llops 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 tracks. Each has a speed of 9 t *bw i.w-i40 a/ppobnf ep-1wq11qco5 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach 11p*w.we -1bf/p 0abniqpiq cw t-oo4 each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveg vd-6. nqckqs+h:6ealing How long will it take th .+6ach:v-k6ndgqe qs e car to reach the truck?    s

  An airplane travels 3100 km at a speed 6p hwi06yqz v/(bi (o+0ewbu)1jss xyof 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h fjs(xiois+1zb 0uy) wqp0yvh6e(6/ b wor 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 velocity of a compl7au 2n.mxmxxl)q9 q)qete 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 covqm79x 2amx) q.qlxu) nered at 55 km/h.    km/h

  A bowling ball traveling with constant spee9(q7 5p +e bq+wys9;ekysdglfd hits the pins at the end of 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 rdk s5eyqqpglfwe++; ( 7y9bs9 eleased 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 6.2 s. What is its aver2n :w0ux eqk c+zs 2vka5h,yiu75 8rgoage acceleratio ak7:r5uu 8+w, 5evy2 0cgqk2nzxos ihn in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelera o:sj 0twrulb(x 4p zgd*7r,7utionsurd :up tr0,47lxbz 7(o* gjw
(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 acceleration1xzxn-j32 0erbv*hpwmb8m9vd u3 d g 9zl-2fa of abou0dxhbm*we2l2f nzdb v xg1 p-9 3vjura m-z839t $1.6 m/s^2$ 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 spee0+e e05hyic*xa4p 12sbn zr zpd travels 110 m in 5.0 s. If it then brakes an 0aenc*y54 bx1+herpszz2 ip0 d comes 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 at t = 0 and moves in a h7q 2 wj-h5et kmzh8a(straight line, is given as a function of time in the following Tableh2mhta(jhk z-q8ew7 5. 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/s to 25 m/s in 6.0 s. What was its acceleration?wdhlqo 55b i 0sdr+ 1-1h/fuab How far did it travel in this time? Assu+1 b -iq5du sa1hd5fowlbh /r0me constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distaae:b7 l;kdkzd hw95: pnce of 85 m. What was its acceleration, assumezlb:k5ad; 79hpwe :kd d constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long nly.cg 6x68o ja runway is needed if th lojx6.y68gnc e (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essenti 1fz6+k3 rwv)x.uqdia ally top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this spr +1q.vfawrkuxz 3)di6inter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down unifldud1 -7bia b0ormly from a speed of 12.0 m/s to rest in 6.00 s. How far did itu0db lbd71i -a travel in that time?    m

  In coming to a stop, ab0lsizv -, (hg car leaves skid marks 92 m long on the highway. Assuming a deceleration s zb-(v0,lighof $7.00 m/s^2$ 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 compreu6)q 2p1oxcja zr) 6ywk4pz6p sses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi onq)k26 cppazr z )xp6o4wu6j1y? 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 cazubx8j )yd(ca 0he(5pr with an initial speed of 95 km/h and human reaction time of 1.0 s, for an accelerat(8x d)hz( uya05 pcbjeion
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance of a car :y0diimaut0 4.e i709 nwbvlt 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’sn0d+ 45hx2c5y-;g sdh clgacy driver looks for an opportunity to pass, guessing that his car can y5+ c4haghcc2nsl5g d0d y;x-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 complete the 10,000-m run in less tha g zs8sv6i153m 8bf0g5djpssb gn. g,in 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must th8spgn1.bgv5gij i zb683 g0 f,m5 sssden 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 oj (lu .n4 va(xw-sf-ikm/h approaches an intersection just as the traffic lightlu (xij-w(s4nfo.v - a 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 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 then . o4/iywxue p;5h.qk ground below after 3.25 s. How high is the cliff?yu;nei5hxwq .pk 4o./    m

  If a car rolls gently+ xliivw5zg uno 7kz3j76o60c ($v_0\,=\,0$) 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 aisf 3o qtq189aykkj z1,r 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 a ball 3.0 s after t1 tf7mmz+fnirt.0gp 4hrowing it vertically upward. With what speed did4 zf .rf+71t tnm0gpmi he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Drawox3x +u346 ltxgrh/ccf4d *oj graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resoc+udgh*3l 6txorf4x3x / c4j istance.

A helicopter is ascending ver5w (zti xllc33tically with a speed of 5.20 m/s. At a height 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? [Hinwl53xc3 (zitlt: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, u,rossc1uv8be 7hx+ . show that the distance traveled during each successive second increases in the ratio of successive odd integersv7ucbo, s8 +x e1r.uhs (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball t5esljo99mkkw0 3 s c8zhrown vertically upward with a9skeskjc9 0w 8l3 zm5o speed $v_0$ 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 tv; l0q: y+owb 7fgd3n18.0 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 bx5e+w- uj8 ryof photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two b +ej-8uxwy5rapple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0 ,r/ngp/84eiql hm s+p.28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did thmgp/4rpi8q,/n+ h sel e stone fall?    m

  A rock is dropped from a s. woq a /fv tez/.ey,qcw:z23mea cliff, and the sound of it striking the ocean is heard 3.2 s later. If the/ we.tzamyvo qz 3q,.w/2f: ce speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garde poeg3l1gze f-ms16g217t lm nn hose nozzle for a hard stream of water. You point the nozzle vertically upward at-sgo6g32 l7m1neltmz g 1pe 1f 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 the nozzle?    m/s

  A stone is thrown vertically upward with a s 7a.by 9fno6o;ycb8ym peed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–y8y m;ac oy97b6f.bon34).
(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 with a vert06)p4 qvdtm smwjyr: 7ical speed of 13 m/s If the ball was6rm7m0dvw q4:jp) tsy 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 functir9 n( fj s2 ;6rrjlsn2av-v,iion of time. (a) At what time was its velocity greatest? (bin(jr-9;fi2 nvs6rvsrl ,2 j a) During what 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 as i;yid9;a1sx ha function of time is plotted in Fig. 2–28ix yi;sh;ad19 . What is its instantaneous 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 f.s- mnaqdj.)l 5e:; xbr+j rqh-t)taaccelerate approximately as shown in the velocity–time graph of Fig. 2s -h xe: fqmnjqd-.tt)5a)r aljrb ;.+–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 (Fig. 2qj +yki*2xxe +–35) w+ei+k xyj2*xq hen it 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 the object traveled durinbu f3 ;0a94cap,ouf ahg
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph fokmlbw1-i ;7ezikw;j9 r the object whose displacement as a function of time is given byi lw ew;;k1k zi-mbj97 Fig. 2–28.

Figure 2–36 is a positionhrslh e8a/2k+e8qjod mwp1 4v8kir9. versus 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 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 int8i k1.mr+a/9der8 o4vh k8w2slqe hjp erval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firevakrz 0g e(kwr( m7derxg;p(l (c,g(:fighter’s safety net. :egwk; (a(r kr,xp0(rm( z7gd(celgv The survivor stretches 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 to gravity on the M7 pdl39tltw h:oon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many timelt379:ldtw h ps higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained +xqow4ppo :5 3lxv,r( bs u2rsby an over-the-shoulder seat belt has a good cha5rxbvu s4w+( s32 op:qrl,poxnce of surviving a car collision if 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 standin1uru(* jej id;g on a bridge, 12 m above 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 p;e1djir* u(juoles 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 tested its cars for front-f /3r9s;-u2 aswmyvzf; qpfe/end collisions by hauling them up on a2/eauff w -3fm y/rq;s;pz s9v 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 about,cx l+ftc0x;ml;ed 5kqln8 p+fq - ch1 $10^9\,km$ 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. 7wb9jserz4,c 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. crjb w7se,z9 4What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a divibfa5)qq 7hie / h4dt2wuo78hzng board 4.0 m above the water’s surface into a deep pool. The persond 7e)thu5q4 iw2fzh/b oq 7h8a’s downward motion stops 2.0 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 transit system, it is necessary m77fm sb1b w/qto 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, calculatbqmbf/ sm7w 17e 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 wings56d z2 -h rlrdqbb*e4m and free fall straight 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 perform evasive action, at what minimum height must it spot the peli*d l4b6br5eh -q zd2rmcan 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 :xjs4 2hce/t6so yb3 wthe 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 dob4 stc:jew6yxho / 32swnhill, 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 traveling at a consj0.dj:i,k nu wtant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from r:0u jjdi. k,wnest 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 secoo3:eebr9h+q h nd stone is dropped 1.50 s later. How far apart are the stones when the second one has reached aq 3 h:h+ere9ob speed of 12.0 m/s ?    m

  A race car driver must average 200.0 k;fm4p,x1c ot ym/h over the course of a time trial lasting ten laps. If the first n1 , ptfyxc4;moine 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 7 z5jqdgtu td4zz eq2r6r6*i*as he moves at 18 km/h .zq76u6t2qdzgrt5dz4 i*r *ej At the 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 6,gh :e gt-xgstwo trampolines. The first child can bounce up one-and-a-halsh: gxgt e6,-gf times higher than the second 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 1.10-km-long train traveling in the.e1hbrk00x64)c7zyejk l t nn same direction on a track p e4n7keyb l0 jcr1t) k0xn.h6zarallel 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 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 basebalzflgf9 fjm48l sm;4+c/lrsbyw k46 +ll with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from beh/l4m jw ls6lf84+ fly;gmsc9+r bz f4kind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleration : 9c (1nsigdrdof $3.2 m/s^2$ 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 has a trafy m1llfyby5, 4hh2 yt6fic 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 lightf5by1 ly,hmy6 thy24 ls 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 a constant 120 km/ l2u+cghy7kuw5b.oh9 h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaininlg5b 9ch.u27+ ykuwoh g 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 a vkc/lkz1w++ qu2(chvw i87lubuilding; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 mv7l12z (wwkuv+ kuqcc8h/ +il /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 sameae*gxs lz.6w5 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. ws5gzx* ae. 6lWith 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 woa,9eisr hpd87uld it take a free-falling parachutist to 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 i987e sarph ,d.)
   s
   km/h

  A fast-food restaurant uses a conveyor belt toginf 374,-ttd n5xhya send 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 spaced 15 cm apart, what is the rate of burger productf 7gina,3-xht y54ndtion (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at1zz.y8 /e jktoy1un ajcoj p5 u+hg9 1478udmb a speed 1.5 times faster than Joe can. How many times higher will Bill’b8y7um .1uka411n u/j58d+pyz 9jhzo ge c ojts ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on;rthhanb-af pqxdpxe -*32-/ the ground below you. You drop a ball from rest and see that it takes 1.2 s for t /hdn3a-xbpr- f2*q -ph;axethe 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 friend threw the ball?    m/s

  Two students are asked to find the height of a pi8: ./ :6my,f 9 plwjkxlzzefrarticular 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 fallpy,. 6wz:8lf:fi zjk /rmx9el. 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. timegg8obkj, 22xv)jve+ e 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 thgbvj j e2 2ex,v8kgo)+e higher average velocity?