Does a car speedometer measure speed, velocity, o ; ai ujs-xk2haxq tvu 962ysx6w9(1lor both?

Can an object have a varying speed if its velocity is constant? If yj,e7ju) oxlm q4)ev; 2k 2ihexes, give examplee,k ml;2hxo ijqxeu7j 4v2 ))es.

When an object moves with constant velocity, does its average velocity during an03xcc-6xqvw-/c;+mv 6s.p nyxsh nk sy time interval differ from its instantanx+mx s wnks66vvqsnx ;h0 cpc3-.-y/ ceous velocity at any instant?

In drag racing, is it possible for the car with thei wbt9*u/ b4qsc8 u8os greatest speed crossing the finish line to lose th s8wqs4ci/o8t *b9buu e race? Explain.

If one object has a greater speed than a sececs6nuesj9l ,1 aakdst:jb8 of)47 f)ond object, does the first necessarily have a greater acceleration? Explain, using examps)69 8:, sjue7fad 1fl ectboajns4k)les.

Compare the acceleration of a motorcycle that accegsx23y;d( rsnlerates from 80km/h to 90km/h wi;s3ny (rx s2gdth the acceleration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity anofu5z ss7 wyd*9.p/ked a southward acceleration? Explain.

Can the velocity of an object,e r aa*3 7oqnyt 3bsr4f bbl;-aj2e9o be negative when its acceleration is positive? What abo bar*oaslq ro9a3 b 3fnb2ej;4-7e,ytut vice versa?

Give an example where both the velocib8cwhtpvs-u 21ofru h3 pfnkf((25s+ty and acceleration are negative.

Two cars emerge side by side from a tunnel. Car o+uehoe,u7uys-nal(biani z 9583q* 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 o a s9 ibqno*,73unoh 5ui-uyleaz8e( +ther as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration ded:f, eu,r)zo*.6 bkjflvoo0xcreases? If so, give an example,oe vj0xr:of6.uzd f,l*o )bk. If not, explain.

A baseball player hits a foul ball strac24 a jp1 mijeo+26nbgight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistanc+jgb c ao 4m6212epjine, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to itskcw 75;trx -bf acceleration due to gravity — does it increase, decrease, obrct-x k; fw57r stay the same?

How would you estimate the maximum height you could throw a ball vertically upwiz84 2cu)7l, /lfoujr 7qi ijward? How would you estimate the maximum speed you could give i )o,jufzciqu4rj2 iw 8ll7/7it?

You travel from point Akgm)ss)s v; o- to 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 speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ?kss;) sg) om-v Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertjy1gaz8)(xspnrh +b;m9 m.r ls o0j9tical string with ten bolts tied to it at equal intervals is dropped from the ceiling of ta r98 mgmjh( 1lp)rtb+sy0nxz;9. jo she 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 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 consta; u- ubabm)dw4nt acceleration: a rock falling from a cliff, an elevwbda-)m4; uubator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original positioy8 sy+ sbhb/i/dh):b gn 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 acceleration due to air resistance is always in a direyhsys/8h +idb /b)gb :ction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same time:oz hr apitn,7r 5):dj? Give exam ronh:dzr5 ja i:)7,ptples.

Can an object have zero acceleral* hpave/h8m 3qd oygf2 5qo/7tion and nonzero velocity at the same time? Give examplesho qa/ge5po*l73dm 8 vqf2yh/.

Describe in words the motion plotted in Fig. 2–28 in terms of /vis /*zuurw*s224 h b8bd x:)lyptfg v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving your hand.z4lubt2 ss/d/fp8 h*yiv*)wu 2 x:grb ]

Describe in words the motion of the object grarhl e bu,/:0aa/qvp 7iphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25 hqhdxidcf67mj 23hg9 /+*vlas?    km/h

  A bird can fly 25 km/h How long doesfz(w h.-8deyp(:*f bs(fkgij it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 jlugj,- j j xbu;77dn.s, how far do you travel during t.gbj7n- 7 juxd;l,jujhis inattentive period?    m

  Convert 35 mi/h to cpenmudgw;l ), 4fm 6;
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves ft+ swvofjd ( nwh3.(f4rom $x_1$ = 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 cr/ j7cut*f)sqhv:te//a3 4o( mayoj /h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home aft/3 m j(h7ayq* j /u c:f)t/ecvtr4saooer 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, every five seconds between a lightning flask5q ipq 4, v7nom1m7oih and the following thunder gives the distance to the flash in miles. Assuming thm7ink q15oov ,m74i qpat 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 lapmtdc2v94;m py s around a quarter-mile track in a total time of 12.5 min. Calc 4t;dv2 9mypmculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight linxc7 .-2looiw2h 9fvrxnkd,9 h e, moving 116 m away in 14.0 s. It then turns abruptly and gallops half9c2 lfn2h.x, 79oirdoxk w-vhway 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 952ln1cj0 ;7 aevgbs1 qs km/h witevcgnj270b1 aq sl1; sh respect to the ground. If they are initially 8.5 km apart, how 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 traveling qjt87p7cf0mv How long will it takf8qm77 p0cvjte the car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then eflbvhuj(+ bciwe15+el4/r1 f ncounters a tailwind that boosts its speed to 990 km/h for the nex /(1vejf+ri4 lufbhl1bec+ 5wt 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 averagg l2bf m+9xk- mq7kj 0x;zhmxmi*1c (ee velocity of a complete round-trip in whi 0x mk;il-xqkfh (z+e297mcmgjmb*x1ch 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.    km/h

  A bowling ball traveling with constant speed hito5nyz/vg) ;t+- uuyy.o8r mc bs the pins at the end of a bowling lane 16.5 m long. The bowlo ur+o5m8-gy;zcb)nuvyt. y /er hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is itspt 9ax t:3jnth(ozc90 average acceleration in jncpt 3o t9ah 0:xz(t9$m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What isjd -s pls8/bki9 /dv1f her acceleration 1sd/dkil9s8 v -bf j/p
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a /r7j9gr)ct u qsu60uoparticular automobile is capable of an acceleration of about9rr6sg)0qjuo7 u/t uc $1.6 m/s^2$ 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 it then bi4xi e.besfxl7 fv8z2rg:mg)l n8w 59rakes and comes to a stop in is zle8 9)xvbeg f57.l2f8xr:n im4wg4.0 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 aw hhyai1x* z()bjx zqkl38:5c t t = 0 and moves in a straight line, is given as a5bx )*h :z a(iqxl8yh1jwz3 ck function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its accelerat x):qlm9yco0 ssk8 )vdion? How far did it travel in this time? Assume constant acc0m y:xq9o)kvc ls)8 dseleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a t6ca i/ tqp4+xfrg33ns+fhd0j2/fvn6j* hzudistance of 85 m. What was its accelerationdn/hcfvzjpt/r* +3h nsfu3 q0xi t+ aj4f6g62, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. viv.5f;z3zys:oki0y How long a runway is needed if thz3z;:foi0i kvy 5y vs.e (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed (ofz0 7) vznrvci-be3chr b(8:fl about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and hre: f0 cb 3v(ncl78) bzviz-rhow 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 re :;v9gi xa554xil-unv9sh wthst in 6.00 s. How far did it travel in ;xwgl his a5-9i5u4h:9 tv vxnthat time?    m

  In coming to a stop, a z m3wr3+hldu1pm-soi4j;/d x car leaves skid marks 92 m long on the highway. Assuming a decelerationd1m- xi m3uh3; /wop+rjdl z4s 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 frn -+yopt+xe f3ont end of the car compresses and the driver come e fp-ntoxy++3s to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car gt;:tafoh )4dwith an initial speed of 95 km/h and human;4ht t)oa:f dg 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 stopping dcj yb jf2+ft.(i3k .kxistance 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 fo ,ha9kt 9:k)h5w/ pzj m3yckclr an opportunity to passpmk9t y) 5kj 3:zwha9cc/l, kh, 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 complete the 10,000-mdjh n lvz)4(7 w:eckf 2vkw7r7 run in less than 30.0 min. After exactly 27.0 min, there are stl7wrjzce vv:k47 f h d)7n(w2kill 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 cbbs) xp66q yd:ar at 45 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross y6 :xsbb6q)pd 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 au3q5eilv -;d v,g4x yr cliff. It hits the ground below after 3.25 s. How high is the cliff?x5rv y-vud;3 ei ,glq4    m

  If a car rolls gentl i w tyaze0j8nmh9.n58y ($v_0\,=\,0$) 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 intor*.br 4aswuj a5sp)2z the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a 3c dy cuss mif0 a.ex,*:-rnj6ball 3.0 s after throwing it vertically upward. With what speed did he throw it, and what height did it rsc3y j : c. sa,*-mnrfix6deu0each?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. 66xiui z9u2bs(k cq c7Draw graphs o6c qczi97s6(k bui2x uf (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 resistance.

A helicopter is ascending vertically with a /i/(3;3gtr krkuq;(qh /yjscout m8 gspeed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a wircj8/u;yhqkos(uk(g/ qt t 3 ig mr/3;ndow. 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, shi *.8fsw 0xpdpn* c9pzow that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5xc w9p*ds 8 pzpi.0*fn, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algeb3 c wk+0fjnp3gc + x)lw7txe;araically) that a ball thrown vertically upwawce3kg a+t j+c fxl);wp xn730rd with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertks.t1n saz i8d0d,)u wically upward 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 apple in Fig. 2–18 (ormhue(y( 5hc+ w number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the uncle echhum(( w+y5ar ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0x ;y-6s 6tq6kzceqtg* .28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the win6;etxgqksqt*y6z- c6dow did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the oce4 cl-5:doajgm *zf)xj2wtcs/g)j5tyan is heard 3.2 s later. If the speed of sound is 34s:g5j2m tyfdjc-xjzg/*5lwo t) c4a)0 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a har3 2uus(+ xm .bkyqoj-22jibwvd 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 vku2 swjm3y-qj(o. bivb22x+ uertical, 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 speed of 12.0 m/s from bnad3 u ) f(7amgzy/s-the edge of a cliff 70.0 ug/n- z(s3)b7ayma fdm high (Fig. 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 pasize-mg(zk0oh ,,dkr6 sny2 f 83lf zc7s upward by a window 28 m above the street with a vertical speed of 13 m/s If thn i20ke lz hfm,fd- 76,krz g8osyz(3ce ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a t1joj7ec :hv*zrain as a function of time. (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 of the acceleration z jj o*:ehv1c7greatest?

  The position of a rabbit alonghb)i6tw(:m:o ctep, s a straight tunnel as a function of time is plotted in Fig. 2–28. What is its instantaneou hps)o::tbetw ,c(m6i s 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 in t*onge.eu(3g ;t w ;kqihe velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting o t e(;.keg*owg qni3u;f 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 thohx,psgl0drtx9(qe y1),bt n nw9; w+ e car in the previous Problem (Fig. 2–35) when it is iy rl 9pdn90+ tn,xtshe g(xb1w,;o)wqn
(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 travz/h- nvez :m )vcy1py:qf ul6-eled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacpnk a89h-4ghe xmg.e 9ement as a function of time is given by Fig. 2g8 n he99ek-hgxm4p a.–28.

Figure 2–36 is a position versus time graph for the motion of an objep+uf), zo,pt+x om,(d: somehct 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 spee(f)d,pmuxs ,:mzp+oo+ e ,tho ding 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 interval from C to D.

  A person jumps from a fourth-sta:k,e+zn,)0ne gc rmmr( /cb 4xrf1 qkory window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before cgnckk0 q fmx,+m br:a4(n)1re ,rez/ 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 ua(aq9tqrs kaa.3- 7nto gravity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming a q9rnsa qa( 7-uk3ta.the same initial velocity?

  A person who is properly constrained by an over-the-shoulder 4x djonx1)ic8nodp.+seat belt has a good chance of surviving a car collision if the deceleration does not excen) xc1o+.8ddip joxn 4ed 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,(j lsrh/( ozebn6dlg 7l qan 2-64qu7v and his pursuers are getting too close for comfort.j 7bvo(6(s7len6 lqdn-hqr/a4g z u2l 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 when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions by haulinlvul77e pf;b -g them up on a crane and dropping them from a cer-7p;u lbv7elftain 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 kb/gpkrrzp;6 2nk gb:md0s),travels 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 uniform acceleration from rest. c+;+-s3fvt 9 dnj:vhbj yb, zpThe 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 be the speed of the last car as it passes the wor s ++ytf:,bvd 9vph j3c;zj-bnker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m a4,vjgm9-. e3hsi l. iihac(mibove the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under t,hli(3mghv9 jm .ie-isa4. cihe water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it ixe66sk42sm5zp ig, khaqa.(us necessary to balance the average speed of a train against the distance be6i 6mg(a.2 4 exqpkhsz5k,u satween stops. 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 down when:l uy35ajt7ml h9:tkt 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 act my9u tt:5jll37th :kaion, 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 wh t1zm,20x w4 ymrzrl-xich 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, puttixx 0l t1mmwr2z4z ,-ryng 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 ho55x, s/lqt1d6qawn iol.:-q+fsze dmp on a freight train traveling at a constant speed of 6.0 m/ a5d1 s,i.f5/qqn 6lwo:d- exls+zm tqs Just as an empty box car 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 of aleux wog;7mj3 ,p m7 93l5ja:ojl-iua high building. A second stone is dropped 1.50 s later. How f7uam9x7 l,au gl:l5e3;oi o mj-pjj3war apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must aver-zzbvmmo1mxb2sj 2 1 /age 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . whbx1jzm21zo m b ms2v/-at 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/fd:,urc lz: )ah . At the bottom, 4.0 km farther, his speed is 75 km/h:,lza r)fcud: . 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 child can bounce u:z c. ,z,xxw;wmmjj u.p one-and-a-half times higher than the second child. The initial speed up o.ux j :x, mcwm;zwj.,zf 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-ldf4/ k 7,s 4vb,xtfhhsong 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? hth74vb, ,4fsk dxsf/ 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 with a speed of 44*i dsn9;3:cm -yg9qtbf* rdf z m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during tf;fdi*sbn q mr9c 3g:tzdy*-9he throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an a(e,tax k9tl7icceleration 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 intersecb3mj7y7gd; fng29*md4 zc luction 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 intersection, all the lights turn green. The lights are9zu;m2 d gm n74lyj*fc 3b7cdg 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,o l eitd7+gl52unys2kt 5jh3/h takes off in hot pursuit. The ,l5k35ulj7sgneo 2ittyd2+ h 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 a building; 2.00 s a/1g-;hwu-juo d7 u loafter that, a second stone is thrown straight down with an initial speed of 25.0 m/s and u-aoowlj7 ghu1 d/;-u 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 th16a*,,a5ulm6hu gvstchpl/ng en *2 fe same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thr g n6f,c1 apml*, 6a/t2egsuv5huhn*lown 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 resistan-rg,- c)mf)m o/p)rtha9 ycjgce, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will gtm-) orj,9) /-yfpa grc h)mcpull 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 togje kvdu is*l-n33m /( 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*/nlv3dm3ije(- s kug the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times fasbv.r6zq7e89 u:s ykq jter than Joe can. How many times higher wiz es9q:jqv6.8r 7ubk yll Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while y71q ejfc0r+8ntc w or;our 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 friend threwftjo70c rn1 rw; 8qec+ the ball?    m/s

  Two students are asked to find the height of a partiovk s4t /p9 /d(qzgmi.cular building using a barometer. Instead of using the barometer as an agp4i t k( mdo/9v/.qzsltitude-measuring device, they take it to the roof 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 vs. time graph for two bicycles, A an.at (te -cm6u ccvn1o*d B. (a) Is there any instant at which the two bicycles have tn tumvatc (c.-o16*cehe same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?