Does a car speedometer measure sptqro-lgi 1 2-weed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yoy75 ns+hk, oyes, give exayo+ksyo5 hn7,mples.

When an object moves with const8j;k*l eo 5wg2wmhp)ew1vsa6ant velocity, does its average velocity during any time interval differ from its instantaneous v5lpmgvae) wjw*1 2k h8e6;oswelocity at any instant?

In drag racing, is it possy .1fzo)* hwdc+eqh5 f:c fvy8ible for the car with the greatest speed crossing the finish line to lose thec*1oyc hf :+dfzy.q)ew8v5hf race? Explain.

If one object has a greater speed than aq ,fm- mx-h 8)igl5hfq second object, does the first necessarig8,-xli mhff)h qmq5- ly have a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 8,wpb my*x,* uj0km/h to 90km/h with the acceleration of a bicycle ymwb,*u ,*jpx that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocitywk/n0ho p.,fn and a southward acceleration? Explain.

Can the velocity of an object be negative when its 9z;(r+;zormf:wq9 ejpjc ne8a (e xn0acceleration is positive? What a+ z9zrece(e;:axp(jw nomq9r ;j0 8fn bout vice versa?

Give an example where both the velocity and accelerati (gx-e-u4male ,wt e+son are negative.

Two cars emerge side by side from a tunnel. Car A is traveling with 3, c) yqmz0evba speed of 60km/h and has an acceleration of 40km/h/miz3 cbv,e0 qym)n . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its accelerationg fdpa .0r/o u0ry+y8u decreases? If so, give an ey 8fu0./r +ro0u adgpyxample. If not, explain.

A baseball player hits a foul ball t0vpw q ,6uhr0straight up into the air. It leaves the bat with0,0hv w turpq6 a 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 happenin4. c q6zytuh2rd+q;c g ur9t3mg to its acceleration due to gravity — doe q. 4z c;ucqd m+rhg96utr3t2ys it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertically u fmnn22+x,k6tms)b5btd i bszuzb g(1i4jr0 1pwabbijr n0b5db 2+)2u (,skz 41xgtmzf 6t1nis mrd? How would you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving atw5eye + x;mnoo s4a6b3 a constant speed of Then you travel the same distance on+sw o45y 6aeb3xm;e 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 why not.

In a lecture demonstration, a 3.0-m-long verticalcuvcpl80y r6dp (4:04woasibjas / w 8 string with ten bolts tied to it at eqaro/ayl i8cv4jbc08ds(p0w4 pwsu6 :ual intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or 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 no sju zr,x*mkjo)so43gyj(. q2 t at constant acceleration: a rock falling from a cliff, an elevatorzxouq,ojjsy jr2) (mk.4gs* 3 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 u3 p px.u9i9qaj(bgno ,4zla) wpward will return 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 acceleration due to air resistance is always in a direction olpq b, azwp.u)gaonx93(9j i4pposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same ;s-lj jb00gbutime? Give e;b0us0jb glj -xamples.

Can an object have zero acceleration and nonzero velocity at the same tim-yd: sb1t5zfn e? Give examples.5yns1: dt-zfb

Describe in words the motion pl ujhd v0rdw,i:vvuv 84r;* o)dotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotte8,;0* i hurv :d4v)vudvjdwr od by walking or moving your hand.]

Describe in words the motion of the ob1wf qm3q(48o(:in lszprk9 grject graphed in Fig. 2–29.

  What must be your car’s average speed in order to tra,jidhss1dr7 be2:) apvzr 93y vel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How 3r nl.u//sb viu2ynb1long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to them27yes 6h 1 svs6(nq1jw wc2tg side for 2.0 s, ho66 hgyj 2nswsts1(cqwe vm21 7w far do you travel during this inattentive period?    m

  Convert 35 mi/h to ;heul..i *sr l;g0 focz oyt:fv1;+wg
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves f,jk 9q 5fw q-uqvik)g8rom $x_1$ = 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 t+x8kuqlvp 1 3nhen begins to rain and you slow to 65 km/h You v8 p3n1xq+kul arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five bzxp*lo)+bh5ax/l* z 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 essentially no lx5boha/px)*z+ *l b ztime 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 of92 ismrt6)*mwz y.k2 ji8rz su 12.5 min.wsus98r2zjik.m *6z )iy mt2r Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight linx843 iy(v9dd xcbe2at e, moving 116 m away in 14.0 s. It then turns abruptly and gallops2(3dyixx 9d4c v8taeb 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 sku47abbrqr * e9s7 ,ogpeed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they rr74bs, * ru7eaqk9b ogeach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling H 49bsdo ljwtibk*3nwj9 bdt1(9e,y t. ow long will it take the car to reach tw.k3db 9*i(otn4tdt1bs 9j, 9e b ywljhe truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters aq) zr,;)ecez;0cridp87;j js jm+6 drpxok3 l tailwind that boosts its speed to 990 km/h for ejz) rjm3j)d; ecq;6;zs ,rikpx8cldpr 7o+0the 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 complet; 4:ij/eswc afe :c8iqe round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the w4/ce aies:q:8f;jci return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits tw9.w: kmuzslc6u1o y7he pins at the end of a bowling lane 16.5 m long. The bowleso.6z 9: y7ukcmwuwl1 r 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/3hnq(l ;qv . hbw*-u*bcdl ,uqjqjm) 2h in 6.2 s. What is its average acceleration lm2q* d.qjvuwjbucql(b*h )q;,h- n 3in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in i.eghcv7(-1y g u0w0mt- dptd1.35 s. What is her acceleration.vd7-g gm0 0duhi(ycp1e wtt-
(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 a7x/dsw,ju9l6 ccoh /v*fo -n an acceleration of about vo*uw6sc9l7 cno-hj /da,/ xf$1.6 m/s^2$ 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 o)ao8sm 2hin p v+xmsi+)s 5m.s. If it then brakes o+5n)iam2hmssx8 +v.pi) om s and 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 = :dz / 6iu7:yg8ddd vdj0 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 z ddu6 jddd /yivg7:8: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 acceleratiomlf;p4r/w)h :udiq, j n? How far did ilq4:r)p ;,/mujwi hdf t travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to r(yz hyvfb:srro96d5 1est in a distance of 85 m. What was its acceleration, assumeb oy9zd:5fhs 1vr6(ryd constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway /gmdo* rsvxn 7n*gh 37is needed if the (constant) ac smg*r/dnn 37 g*vxoh7celeration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top spec77 j-jk9 tmosed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does ij9j-s7tmk7c o t 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. How fal oc; -cq;3qvzr did it travlc3oq- cq ;;vzel in that time?    m

  In coming to a stop, a caymly p7 .m//dar leaves skid marks 92 m long on the highway. Assuming a p d /m./yylam7deceleration 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 v::8engu rjyrb0voq wzswa135) o2 ,t the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express toz n:ojt sw,0)ragq2y 5wb8ve:3vur 1he 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 initial speed of :)* ej0pep8;n dc*jot0cgkq e 95 km/h and human reaction time of 1.0 s, for an ae:0gc*0kp 8o;d ntje)*ejc pqcceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distanxriq7xv:i0a4kx-6v n zj:h)8-re getce 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 r: eplhhua7r7 n)jy5*looks for an opport*7hnrr )j7pyuealh 5: unity 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 complete the 10,000-m run in less than 30. 9lerg(i3 opnkj:2o nk/1g -mz0 min. After exactly 27.0 min, there are still km3j1 li 2o(- ngrzokg9/p ne:1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an interseco yb:wqrzf*c/5j20z j 1owbwqee1s - /tion just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximw: wy-eqbq1fzw2crj0*b/ojoe sz/ 1 5um 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 th qw-;03efsq(* xufnn c w5pud*7oo:uce top of a cliff. It hits the ground below after 3.25 suw o5fq*d *-pfq nu:esuw ;7o(0c3nxc. How high is the cliff?    m

  If a car rolls gently / f1b8)tk is yizhy wrxe6x/,/($v_0\,=\,0$) 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 st e2+t,mhb9qhfzvz, o3raight up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s af gb)24hl ano;ft 92duqter throwing it vertically upward. With what speed did he throw it, and what height u24lbhgo ta; n2 dq)f9did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest an hml4,y9.og 6 hnm/orzd falls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from g9mylh4ho/,n.r 6oz mt = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a sp wepf*q+6lo h5s0b0wn eed of 5.20 m/s. At a height of 125 m above the Earth, a package is droppe500fbnohs 6e*wl p+ wqd 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 during b1:/xz: )carzqqq* jo each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first sh)bjqa:zq *c:q1 ox /rzown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglect*9pfir5vie nk/c-b q. ed, show (algebraically) that a ball thrown vertically upward with a spe-cn ipbikrq/*9vef. 5ed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speewju7e ks39l 7bd 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 photofgflot( lby9 f0 8wl09im8* e*lqhgag4 lash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.] aoeg g hlgyw0 l(90*bi88tf9 4lqfl*m
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a wind1sud:0uee pt :7hnnc 7ow 2.2 m tall (Fig. 2–32). From what height above the top of the window did the c 7et :0:u7du1npehns stone fall?    m

  A rock is dropped from a sea cliff, and the sound 07+e uamr,wldof it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff0ma+ ldur w7e,? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of wnz on 2b(ho9;gb(0bw(fm7 h- t nfeyu,u:utt0ater. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is tho(tfbnt u7y;g(( th-u 9n0b0o bf: mw,zhue2n e water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from thpk1*tb)ho7(zn zx78lwkk b f/e edge of a cliff t7/8)phbb* 7kx kzz w1kl(o nf70.0 m 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 pass upward by a window 28 m above m r ,*pcby6o;ov i8g:gthe street with a vertical *i :8gm,6b oovprcy;gspeed of 13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of time. (a) A b+0wo. d(txv ik4h:qdt what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During wh .x(kb qit4d: v+0dowhat 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 a function of :flco9iy t-ker thko*o6.. l/ time is plotted in Fig. 2–28. What is its instantan thrle koy:o .lt ic.-6o*k/f9eous 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 e ls0soo3;4acas shown in the velocity–time graph of Fig. 2–35. (The short ;c4ol0s 3saoe 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 prevcki*q1ut.9 u- gt(qpsb8 tx 8xious Problem (Fig. 2–35) when it is ix-1t qiu cg(tt8*x8q9 k p.subn
(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 travelje hd tv;ajb2m4:7hn- ed during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for thc.xu 0abri.ud8)mj1*rz klm6n uk 99r e object whose displacement as a function of time is givenb)mur xm ci 8.jn dkukar 0luz9r91*6. by Fig. 2–28.

Figure 2–36 is a position versus time65u kw0jq/(wicuu re * 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 questiku*wu5 / qc6ie0 (rwjuons for the time interval from C to D.

  A person jumps from a fourthe5 ;2tmmq5z9 m ugo3jz-story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1q ;mzeju93tg2o mmz 55.0 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 gr/ 8e3-y;w/3fzv(qy9 wetwehvd lp r6z avity 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 the same initial (/ye 6h -3pq/ yw;rz38w fwlvet9vze dvelocity?

  A person who is properly constrained t5 ;hnzdqfluy8/:o+qby an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleruq nh l;:qo/tdy58fz+ ation 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 abovec2rubgmi(58cs ux6r *r tux39 the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles awayrg* u 9r ruc85xixubts2c m(36 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 c 57k2bl raxl9b3 yv vtn ud8jaz+in(5o 2,5ahfor front-end collisions by hauling them up on a crane and dropping them from a c ukvyra ( 7x9b5l2a zh5d nnlc jt8,b+v3ai52oertain 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 travelby;qrr. pb-amvr* ./u s 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 beginc;-j fc vh/1xgs uniform acceleration from rest. The front of the train has a speed of 25 m/s wx1 h ;v/cjcfg-hen it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface into a deep po c8 qbe,m3axbr .x:mv.ol. The person’s downward motion stops 2.0 m below the surface of the water. Estq b,.x.ve3rm:am8 cxbimate 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 to baiq12w 1++qun)ed/ vjle3 tfzsp h /st*lance 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 u sezf11q wl +h +2ditqnsj/ /pv*3e)tan idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fish. Sd;pdahywpqe9 +5u yk6m 2wh42uppose 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 escape? Assum 9k4epw; h2md2py+6yhad wu5qe the fish is at the surface of the water.    m

  In putting, the force with which a golfervxfn q6d4ln/oo.3v9z i:m tb0 strikes a ball is planned so that the ball will stop within 0do:n.lf nqixv6 4tb mz39/ov some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a 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 ar1r- fmnu /zv , pkupw73h+c)dt a constant speed of 6.0 m/s rcm7phk3fwd- /u) ur +n,1pzvJust 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 a high building. A second stozto,ve o ew;,v(;cjw)t/al +w ne is dropped 1.50 s later.o)z eaww vwtt/e,j;v; ,l o+c( How far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the cours/hf b3v+j gnwxm63 vn/, f8glye,co g*e of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintvfjnwn hb /x/lg*vc,gom3 g, 6f83ey+ained for the last lap?    km/h

  A bicyclist in the Tour l/,0fttknl07a +zny z de France crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (00a t,tzly/z+7k lnfnin $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first chil(ito-o*tp(l ;w j(akwd can bounce up one-and-a-half times higher than the second child. The initial speed up of the second chit tol-w;i((j pa k(o*wld 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 u1ruop xp82l0 7v)leb in the same direction on a track parallel to the 2rvx)ul0bp 1ol7 u8pe road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a sp 6 drw/s*wd.axvu9 q:leed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of d.du6l w:9w*rxv/as q 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 the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleration ok 815dd7ziwie :.h6oi va8azkf $3.2 m/s^2$ 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. 2–4n fi m;sm3t d:lv/p/,6dtdo) l2. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose y lddms)6t/l, :o;3pf/vn ditm ou 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 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 spee9 m uvw9ukfxzoijo3051,vp /bder traveling at a constant 120 km/h takes off in hot pursuit. The police office bj om3 pi9kzoxf9v051 v,wu/ur 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; fp4j g )xe1k5o2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the x)fo 1k5pgj4esame 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 time. Tc:kj0*ea i k,dhe first stone is thrown with an init ,0d*caikek:j ial 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 thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-falling n,6u+b, km b0l1uu beeparachutist to fall from a plane at 3200 meeu,6lb k1 b un,m+0ub 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 ;0yd0/j9+xnrnc zszkzui n /;the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2nnn /zx 09j;z/ys z+ir;kcd0u .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 burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a spo5i 0 tprgg6 3bw;p6dueed 1.5 times faster than Joe can. How many times higher will Bilppu503 6dgrwgio6 b ;tl’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your kpa4umq/ b3mso( 17dpw, zr0kfriend 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 fb71k 0pom wdrpu/a 43(,qsk mzriend threw the ball?    m/s

  Two students are asked to find the ippcj vm- /n08-bo2s5 ueq. pgheight of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One stu unpi2-sv/pbp8 -ej.omg05 cq dent 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 and B. (a) Is;(u19 ufvvquv 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 bicycle(9uv fv1;vuuqs 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?