Does a car speedometer measure speed, veloci40* gk 1qibsmaxd43y 0+ xytihty, or both?

Can an object have a varying speed if its velocity is constant? If yes, givhpbk4 bz(rk1s5;i9b f e example; rfk9bzbs5(pih4 1k bs.

When an object moves with constmo:qa+ g bq0q9j /;ogdant velocity, does its average velocity during any time interval differ fr; 0qqog d/+m:qjgoab9 om its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossingx*0pp7ax4z40vewy it the finish l*0zwv ex7 4p0t x4payiine to lose the race? Explain.

If one object has a greater speed than fx7sy 6* pta xh5w1si6a second object, does the first necessarily have a greater acceleration? Explain*51fps6 xs7iawxt yh6, using examples.

Compare the acceleration of a motorcycle thatymyg b8b9y) owu nhoci1 ,/z4* accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates/*o941i )nubowy ,mzyb y8ghc from rest to 10km/h in the same time.

Can an object have a northward velocity and a so 9y f+nstc0.fv ock :7v9xs:njuthward acceleration? Explain.

Can the velocity of an object be negative when its acc-x u;mtqr zp/; v9) mtpy6p-sxeleration is positive? What about v /x-- )tu txpym;69spzv;rmqp ice versa?

Give an example where both the velocity and acceleu-9wxpwek6 00ud mlw ,ration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling wi0 kdl0 6i.ig20 gyhkboth a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reabydg 62o hk0ik0g0il. soning.

Can an object be increasing in speed as its acceleration decreases? If s (eu;+ tdan4+a4r pmbro, give an example. If not, explain.rp4; ea++da m( bru4nt

A baseball player hits a foul ball straight up into the air. It leaves t s,s-jepyk-/d he bat with a speed of 120km/h . In the absence of air resistance, howsk d-ej/psy- , fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its accelcn-n48wl qa)zd mjx-*eration due to gravity — does it8mdxz-4j w)n*n l qa-c increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertica9v/va7*yd;wtdykorts0txb +: ev 6p0 lly upward? Hrv +ddvbe6 at yp*ott;0vy : /0wk9sx7ow would you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant2sd ks2 yzd; wou:wx28wx um8( 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 why or why no sm82d(2wxw xkusyuodw2;z8: t.

In a lecture demonstration, a 3.0-m-long vertical string with j+, jq lrv9px 14ae*txten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on ajp,xrv l+4xa1j 9qte* 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 md;0noucz(u b4q n:nf ;otions is not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fn (cdnqu:z4 ;b; 0ufonifth floor making stops along the way, a dish resting on a table?

An object that is throwl ::exh)4ztum n vertically upward 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 acceleration4zt:lx h:)um e due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the samezrt ;72/ibye 1 go:auy time? Give examples.ra /byi172g;tu:yo ze

Can an object have zero acceleration and nonzero velocity at the same twtlac p b :,cu660(pkz*f2y k8y xwk-oime? Give examplef p(kbt w:8y 6y,w6 kckp2cuo0x-azl*s.

Describe in words the motion plot(ypcj :ewlwe( 7jvmd l8/c )h xw.4uj9ted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking orwldcjjcv7/.9 wxh: 4w)l( peuy8e(jm moving your hand.]

Describe in words the motion o r0+b:vvv-.jc(n v :tob mg;rvf the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25 h?ack2:rev 663dd k1e6s a wjbp0    km/h

  A bird can fly 25 km/h How long doesc s ,mx3wtd.,x it take to fly 15 km?    h

  If you are driving along a straight road and qlfj:0u y )jk9you look to the side for 2.0 s, how far do y )ykj09 ju:flqou travel during this inattentive period?    m

  Convert 35 mi/h to +49 rqjydol r:
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves, f d3 b:.*wkn iqu+avo36wp+a 6qaryu from $x_1$ = 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 9df96jfko wtqq ms 7).o2 7p5zb5 km/h for 130 km. It then begins to rain and you slow to bf9257tpqwmo) f6ok7. sjzdq 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every h d 6u:,.vz0nbw7har gfive 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 time a ban hr:w g,u.7v6dz0ht 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 tot2 szpd 5bh8itvl:os ;+al time of 158 sbi2ztvl ;+ hop:sd2.5 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 aw+ p-yufzwmb8wqd :/ z8ap1pb2ay in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calcul1:/b+8 p2bd uzya-pfzwq8m pwate
(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. Each4+egw14xvgk4 uv,xna has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each othe 4u44 1gkvw,+gaxenvxr? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck tztjr8(;r m 5tzraveling How long will it tak 5 m(;zjzrtr8te the car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then enco+sk*o*fdtfhsek9 . bjbsgs.(w2r* 3 hunters a tailwind that boosts its speed to 990 km/h for ke3rd f ss.bs +g(**w9sjfh2*o.bht k 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 ;uv0/kh.;e(qx zpusv of a complete round-trip in which ue;;xk0/qv (s. pzv uhthe 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 sgfg6n-2z ;bs kpeed 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 released from his hands. What is 6 zg ksnf;-gb2the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from opb:uqe0 bom a5 o2(6z o(4emkrest to 95 km/h in 6.2 s. What is its average acceleration inook 42:q(ezomb0(a 5e bu6omp $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to uv4nrz tp6b*te/6y- z10.0 m/s in 1.35 s. What is her acceleration z*pyn4uz6b-/e 6 ttrv
(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 wo98id qy+m-s an acceleration of abouw9 sqy- i8dm+ot $1.6 m/s^2$ 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 tmv evdm, :0l8lravels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is im:,v le80vld mts 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, w/ nzid/wx(+,zaumd*hwy * 4zf hich starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its v* ,w/d+ufzni/ydz m(w 4azx *helocity 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 6.0kpvl1o 2xqz9 m1(rq l/teeqa0:d* 0qb s. What was its acceleration? How far did1e1 v/:*x kqplmrb90 l0zedao2(qqtq it travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to resrj czs(2o19q 2 u3jhdkt in a distance of 85 m. What was its accelerati3qokds2 1r9 2 h(ujcjzon, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a run28jfawpbo: q1 .xqvsy s. n*l+way is needed if the (constant)s j :.v.2w1nqsq+oaflxbpy* 8 acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can 3hfedy pkz3s1jwi b .bx*ku39d)ch4; burst out of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the b3;.z1y3*9 w fek d hd4pxsh)3ki jbcuaverage acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from*jbhiggixd9 ewt8 8-9 a speed of 12.0 m/s to rest in 6.00 s. How far did it tratji89bgiew*dhx 8 - 9gvel in that time?    m

  In coming to a stop, a car leaveso l-r*-rf* psr skid marks 92 m long on the highway. Assuming a deceleration of ro- sl-frr*p* $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tr(qb)6 e6lczsi+ q qj9tee. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’ssez+)qit6cb (ql 96q j,” 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 s0d -*ess6f(frckuds; * qr7 nmpeed of 95 km/h and hummkddu r*sc 6 f7f(nsq-s*r;e0 an reaction time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for thpyig38xpyn+kg o6 qa*/+juvn.h yw* (e stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The cao rbvdlb /-i(y.6ksa 1r’s driver looks for an opportuni a l.b6dk ybisv1or-(/ty 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;av4 s80 iitxn in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner mustva8six0 n 4it; 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 r8ea*wyv/: iv-dp2 ez u /njxy5r0c)xkm/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 tr2:wvv5xyu jx/z/y ceaned8ri0)-*p ry 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 the ground below after 3 6fvbos(9;cfh.25 s. How high is the cl9; vh 6bfscfo(iff?    m

  If a car rolls gentlyzg+c/cg 60ypj) w-ncc ($v_0\,=\,0$) 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 intocmivnm 9f u,07 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 after throwing it ver2jl) uzwy,9)t q;w;e /bwr mab28zbehtically upward. With what speed did he throw it,,z9jyql2w )z m wh;webr)ba28eu/b ;t and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under t-u;jw rbz2*wf he influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from2wzbf;r*u jw- t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a height of 12tf(+s jwu 4p,k5 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: Tf,u +s4p wt(jkhe package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, s g/sdh/;x1r:p zajcp 1how that the distance traveled during each successive second increases in the ratio of successivc;1ap1rjh/zd :g/xps e odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraic9 c ;mt1bcasg-du0;k;+ j4mn+ btgwclally) that a ball thrown vertically upward wiwb-gd t;ckc;0tlnm bm;1a+cj4g9 u+s th a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18.0 m/sd-g.eep+ tbd0y7 :bbz
(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 thc3 k/m+s+w qede apple in Fig. 2–18 (or number of+ceq/kdw + 3sm 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.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2–32). Fuf:7da:o-sbh puy4 qcb 1g3q 9rom what height above the top of thydpb:4ua:c -uf qg 9oh 3s7bq1e window did the stone fall?    m

  A rock is dropped from a sea cltkt-gmj,l; z1 iff, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 34 jt,ltm1- ;zkg0 m/s , how high is the cliff? H =    m

  Suppose you adjust you 6)/.rc w wbcne-s8kgpvl bvv y)ed,0;r garden hose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is ,bkv)g-cr0 /esvyne. ;8vp)c6wwldb the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upwas7 - u0h(m l nt;jthh51fod+zard with a speed of 12.0 m/s from the edge of a cliff 70+ 7mnutzflah0(1th5-d; osj h.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 the str*i-pkhgtt7f /;fl fx7/1pr wzf:dap2eet with a vertical speed of 13 m/s If the ball was thrown from t /*gti-7wp;2rpf7f :1f pdlzfh/kxathe 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. pc3d ttz+* 5y pv-6ak skgm6o,(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) d5paosy, kg3 kc+6mt6pt* zv-When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time is plot hyf ubks96:; ewmi:y1ted in Fig. 2–28. What is itehyw ::m; ub6yfs9 ik1s 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 accelerate approx)33l.bcv4wimfgw -*a gyf9c ,yg.tv cimately as shown in the velocity–time ga )c .3yl-cf *v9.gigw3tw,m c4ygvbf raph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the yx ejij/z bct 7179ya4previous Problem (Fig. 2–35) when it is injy/z icb71 xta9ej4y7
(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 during+): km h mzeg-*eoim5u
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a fuq+rfz+ 8ec*t.8 zj yp4s r de9c+z5k lz9ta9ldnction of time is given by Figq 5.efpzdzyzr+9cs9 8 ck 9t+ejr t8zll+d4*a. 2–28.

Figure 2–36 is a position versus time graph for the motion of an object bmw7kvm3o i )f6mxs a*:,s8ii 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 interva o:sim7w6, m8k *fv b3imsi)xal from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’s safety vy9n :krvv,5nql z: d7net. The survivor stretches the net 1.0 m before coming to rest,:5vv:9 qvkrz7, nlndy 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 Moon is about one-sixth wha+x 9m )x;oiyxjep 04cjuf5*hwt 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 veloci4h0+ px5) xwmo*ejj i u;yx9cfty?

  A person who is properly constrained by an over-the-shoulder seat belt has a g6 +ahgqf;v: xiood chance of surviving a car collision if the deceleration does not exceed about 30 “i a6vhx:+g; qfg’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road below, and his pursuersr s 15vvw *uftc)k*7vx 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 xku t vs)cv5*7 rw*vf1of 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 ffi e9) 4fv8qx6brff9 kor front-end collisions by hauling them up on a crane and dropping them from a certain f96b kf xf8riqe) f49vheight.
(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 tr /:5f9rz.6ouga-lgi0ys9d8 msd p6 fjmi jv4bavels 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. The front93) wvk( kz78-huwi 1ivp.u:kvrowx l 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 worker? (See Fr1i(lpuik.-7 howw3 w): kzu xvv9v8 kig. 2–38.)    m/s

  A person jumps off a diving board 4.0n,gt b.bj22y wj:g)-xqg1 m(f a4 ncuf; jnxm7 m above 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.qb7gtuxx ,1-4j cgb) ;f(jnfay mj 2ngmwn2: the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapibfo5 bb yk s17oan,,4rd transit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situat 5 bsb,1bkn7a o4yfro,ions:
(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 frg6s:uv 5tte*y(0ey 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 pelic56s*trv 0gte (fyuy:ean to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with whi+3 :vib(.ixvupw 9i2g u1d wdgch a golfer strikes a ball is planned so that the ball will stop within some smawb1vigd.w:v3(p i9ui+dgx u2ll 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 at a const 7s/g)kyr+ ibvh x64uz2fsfc mb6( 1kcant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from resry7kgf uci(v+bzb6x m6k /s 4sfch12)t 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 stone is dropp iwn8s73f sq*zed 1.50 s later. How far apart are the st7iw nfq 3s*s8zones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h oa5qu/hvq*1 (sj8 fkx yver the course of a time trial lasting ten laps. If the first nine laps were don/u 1qh*85sk x avqfj(ye at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de Franvbd3 hn*j9 k3qce crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 7*bjq9 dh3 k3vn5 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bounce up oqo02x-ze g67laiw5 smq;ia t-ne-and-a-half times 2i-wqt5e6s0 molga;xiz-aq 7 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 overzxl c :4cyhb sgv9t101takes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the cax10c yhcgbl4s19v: ztr 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 speed of )- fq)xm2cy zo ef8ra*44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the f *zxer) q-8)yof2cm aball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accelera,;3c a -tbbscwtion of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each intersection has a traf 11xf-.jlqqq o(a wh-wfic 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 tu.w aq w1fqx-o1hqj- (lrn 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 ln55n70mn+w s l2cel embfs)*, passed by a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder n l 5mmb+l75f0sls ee2ncn)*win 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; ln+rb)n35h6 jetdjr 1k3m yz7 2.00 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 same tim6y+j3j7b )nnkdt re mh5z rl13e.
(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 l2v g qr3:97 nu8fkkrn7wyfn1time. 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 velocityv nlyu 9f3n7r2 w7nfq:k1gkr8 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 woul0ma h p:kz v5h,x+am4,5tr jned it take a free-falling parachutist to fampvzhha55a 4: 0,, enjmkrtx +ll 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 .)
   s
   km/h

  A fast-food restaurant uses a conved-:j.eio 3t ;wdizlv/8lhzs7n, qpha7am2) e yor belt to 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? azew .2e3,tlhv)ji 8: nh- ;dp7aqdsl/zi mo7If 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 vertical p *kdy+7-gqx9ukvy1jo4 wp; fi+5m kdly at a speed 1.5 times faster than Joe can. How many timeskp 7k+fdy5*jy 4xq1pko-;wgvidm9u+ higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands 3c(/+-n rr(i-fo wxiiqw lwh, on the ground below you. You d wiixfw-o +qwr( (h-ln/ir3 c,rop 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 threw the ball?    m/s

  Two students are asked to 7s5 x4h2ehmd hfind the height 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 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’shheh4x 7d2s m5 height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, . utu)c w2v-ooA and B. (a) Is there any instant at which the two bicycles hao-u w)2ucot. vve the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?