Does a car speedometer measure speed, velocity, or b fiwir . -boe*8wr 4wn/ouu0 b,v6r9wdoth?

Can an object have a varying speed if its k q0;xvu0-4y6 d xsngb e s-x1wo+hes8velocity is constant? If yes, give exampl0vnb0dhuk s8e4-y 6osxs1x + e;x -gqwes.

When an object moves with constant ve2bsg xedkh/9d3g,0 cp xpy))clocity, does its average velocity during any time interval differ fdkp2/hx3ds) ,)9xpgegbc c y0rom its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossingbjb1s cn5( tnl1) xn+e the finish line to lose the race?en b+jncx)(nb1l t1s5 Explain.

If one object has a greater s9sk p3,hlvse-o ld24 qpeed than a second object, does the first necessarily have a greater acceleration? Explpl q 42hes-,vld sk39oain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 9p*k fgu**o2 au0km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in * pf* uokg2*uathe same time.

Can an object have a np4 9 :w hdwhhkt;vdl1/orthward velocity and a southward acceleration? Explain.

Can the velocity of an object in/ v7 r8*v3g w2n5q3pmztawn n3nzg(be negative when its acceleration is positive? Whazr2*/nz wmp n3 7ngagv(5 q3nwt 3vi8nt about vice versa?

Give an example where both the velocity and acceleration are negative.t6 wx d imwagvdgu3 :w70vb*m9c,: x0l

Two cars emerge side by side from a tunne067 oe-3 ye1co dnhkcypq8 l.dl. Car A is traveling with a speed of 60k 1y.y83eccoqd d0h7 peoknl6-m/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 reasoning.

Can an object be increasing in speed as its acceleration decreases? If sgdz*uc8ezrgcc5 so+.8v 7 e ,eo, give an example. If not, explai zogg5csec8cu*. , +e7zr8 evdn.

A baseball player hits a foul ball straight up into 7*nr dresk88 -d9rhtq:nfd9pthe air. It leaves the bat with 9ts:9n7dn-edrp r rqdk* 8f8ha 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, m, ja f52tz4dgj v.j)dwhat is happening to its acceleration due to gravity — does it increase, df2,4j.jtjgav5md) d zecrease, or stay the same?

How would you estimate the maximum height you could th/gu34x./was/gu qk cnrow a ball vertically upward? How would you cg3a skq /uxg4u/ nw./estimate the maximum speed you could give it?

You travel from point A to point B in ady kb md:te1s mf7 (-fi()je)kys il-8 car moving at a constant speed of Then you trave) f t(ekslfk -i)(1jyd8 bm:-my7eid sl 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 not.

In a lecture demonstr vlrw.vbd(f1t)h9qwi q,vm/r .ivc5 * ation, a 3.0-m-long vertical string with ten bolts tied to it at equal 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 th*q ilc(q5fr9wvb ).v./h t vv1 ,dmrwiat the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock e9c 9y qa4r4fwnry 0ck5-slf b m7lx1:falling from a cliff, an elevator moving from the second fwr feasc1yr4cm7k95 llqy0x4n: f 9-bloor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upwaz w;kaujw7ghp73s ,ai 6 3jkok9:fvzx9dqv06rd will return to its original position with the same speed a z,7 og99dakk;6kups3w6jfj:wv3 7xz q ihv0as 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 opposite to the motion.]

Can an object have zero velocity and nonue na00o q6)tu-) xkgozr pj/2zero acceleration at the same time? Give 0j tp6- o qnaxeuu)koz2g)r0 /examples.

Can an object have zero acceleration and nonzero velocity at the sa8+ eip k*bzd)f0rd,d1s t5rferk z1-gme time? Give exampl zgbd+*-ektr, d01pdf1e r ikf5zs8) res.

Describe in words the motion plog v dta;9cx15xr21hzcyrpv: 1 tted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or movzhdc ry 1xpv5x :t92gc;ar1v1 ing your hand.]

Describe in words the motion of the object graphed in Fig. j k5k-kun5*arq:slx fjp0 7ful-+iu . 2–29.

  What must be your car’s average f*9lka tia* e2speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does ifh3(5x vch 2mct take to fly 15 km?    h

  If you are driving along a straight road and you look to the s qzwmv5d142km , v;zppre*wn gu8k8d*ide for 2.0 s, how fa*nqk2;5zp,w 8dd 1gmv kzu*wpre4m8v r do you travel during this inattentive period?    m

  Convert 35 mi/h to d3c2 hj6qs2ga
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fromw .s/i9skm/j4q6 xj5*xrzy zt $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home from school steadily at 95 km/h for 130 km. It then b llbeka( (b*(oegins to rain and you slow to 65 km/h You arrive home afterleb(la (b k*o( 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)8v34/ 5sou1onw wnacm/:gjqw 8a y hq-thumb, every five 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 at all, a8 q/ vyoa5 ou3mgj/hws8n)1 4:nwcqwestimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps an. zmfyzzyjmg7f2 2 t;lr: 61gd79o djround a quarter-mile track in a total time of gfdn76z7;md2 rz l . j o1y:mjtyf92gz12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trad1k3n,*f kkgs b 8q-yminer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calculate f38-ym*kd gnq 1ksb,k
(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. Eacpbtv b 6c+s6170g4q t wp5irlgh 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 reach15pl7b b0q4igt6 s +rtpv6 gwc each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m 2y1hch;v yjkgv vf6(a45;ew jbehind a truck traveling How long will it take the4 5whhyv yc 2(ej gkfj;a1vv6; car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a tailv*m5iex sbehy d9un :rdwit+) 4/u*bmphg(2 6wind that boosts its speed to 990 km/h for the n*rmmhdeb2dith45+*/ xb p9sniw 6)g( vu:euyext 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 a/vcnny+(j t0mverage velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch mcvjt 0(nn/y+break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hitaiwi+w-b)fy +-xq i 1gs the pins at the end of a bowling lafw ii + )wyq+ag-ibx-1ne 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 the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its 63 nu7bmp3nfw average accelerationpm w73 6bufn3n in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is,ni gg o;(vws cxg/geu8z:z:. her acceleration ggun /8(,o.g ew: cxsgzzv: ;i
(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 a j)nr v (xa(v9x 2b/bt/lw5i5vlqcc g*n acceleration of about ) jg2rbnbv9xcqaw /v5l(vl5 cxt(*/i$1.6 m/s^2$ 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 5e-* caw/omo4:b9z 6a9l1qmfzw 1 oxit .0 s. If it then brakes and comes to a stop in 4.0 s, what is im 19 o1c:6mwx/bz4tawlaq ze*o-fi o9ts 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 fro)2 x-paar;q mwm rest at t = 0 and moves in a straight line, is given as a function of tpawq-a2mx r;)ime 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 mnh.k b)jbobmlv mxvs( j;mrv 2o6-7(+/s to 25 m/s in 6.0 s. What was its acceleration? How far did x ov 7r+nsb6j)b-2vvkjm(m.; lh (bomit travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its acceu aa)z9 6:iwcflerat:6fca)iaw 9z uion, assumed constant?    $m/s^2$

  A light plane must reach aw mohh3m*58 vt speed of 33 m/s for takeoff. How long a runway is needed if the (constantwmm*tvoh 85 h3) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can xoiht n(s7:pnbh5*+g* e wv9 bburst out of the blocks to essentially top speed (of about 11.5 m/s) in the firsttws79*i(v*h:b pbhx+ogne 5n 15.0 m of the race. What is the average 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 a speed rkj)-adt mw9s7h l*c +of 12.0 m/s to rest in 6.00 s. How far did it travel in that - w)sd*a r+jl9mkc ht7time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assumin0 wmxki 6ze8v8g a deck680vmwizxe 8eleration 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 trqrk obar:3)tk 9 92zg3g/usd)wu/ ,9leo lfip ee. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration oog9d)/,w k:fltu s3 z u2i3eb r9groa)/qp9lkf 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 with an initwkt m5e+ wmj,pkf;5s0 ial speed of 95 km/h and human reaction time of 1.0 s, for ks+fk;55jtew0, m wp man acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance og.0sl c7xn/rb n2tm0lf 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. Theibe cbn di4:kw/5ki 75 car’s driver looks for an opportunity to pass, guessing te :i/d5in5kcbw4i b k7hat 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 30.0 min,gb:jrn4- fz 4uqmrs9. After exactly 27.0 min, there are still 1100 m to go. The runner mujg, 4 -srru:n9qzf m4bst 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 i2gvx s rt::fh0ntersection just as the traffic ligfs:hgx2 0 rvt:ht turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the to6 3ki yx: :3q)td)bqfj.wkscm p:ec3ap of a cliff. It hits the ground below after 3.25 s. How high is the cliff? 6 k:x wdjq3i3b:e3 ftaspy:k))qcm c .   m

  If a car rolls gently (g- zztvejksv+5vy5y , 1keo))$v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air with a speed of t*9ip gl p2aj722 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 throcah-dc2is/ .w6qxw cx*dqq i/77;qf i,ks w5 awing it vertically upward. With what speed did he throw it, and;s/q7awadcxiw/s6w-2hx7 i qf5 qck *c i, .dq what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influ1icqu9a32 ie mence of gravity. Draw graphs of (a) its spee2i maq3eu9i1cd 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 vertfv 76 ddcce3ss3u6w+qc(jfi * ically with a speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take fo f6*csvsicd6j(3d u7 fewqc+3r the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from eb0ak m*jch*b08zwsff 171lprest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This wa* m1peh b00abf*78l z swcj1kfs first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance iswjxi 3bb14ei)* (louc neglected, show (algebraically) that a ball thrown vertically upward with a speed iw* l)b1c43bux oej(i $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward 6wl x3l ip4rx/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 (or nua.zpmf3t xo , h00pdd2mber of photoflashes per second). Assume the apple is about 10 cm in0t axd h.opz0d,mp3 f2 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 pa -rnq4rbdfk7ym,m 3iv.3 (kas st a window 2.2 m tall (Fig. 2–32). From what height above the f 3rk ,d(-3isvyb7mrq man.4ktop of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it stz9 6d3(lvpxuwriking the ocean is heard 3.2 s later. If the speed of so9d(lv36 pxuwzund is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose h3bp:emhy:x) 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)3b xe:ymhp:h 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 speg;qb)pd)y: .jq z n9voed of 12.0 m/s from the edge of a cliff 7nyg ): b) jovdq.p;zq90.0 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 wdt) oesm5aun ys()-z +indow 28 m above the street with a vertical speed o(+) au-ts5som)z ednyf 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 functionjrxj0mvv9qse1f ;+p32ro 7nh:ljr m+a )h :ca 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 accej+ m0:qvsr:hma9pj )c f2 v;1oj +reahxl 7nr3leration greatest?

  The position of a rabbit along a straight tunnel as a function of time: a:n0,g 2f xlygupq.b is plotted in Fig. 2–28. 0u: f,:apbg xny.g2q lWhat is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

  In Fig. 2–28,
(a) during what time periods, if any, is the velocity constant? t =    s to t $\approx$    s
(b) At what time is the velocity greatest? t =    s
(c) At what time, if any, is the velocity zero? t =    s
(d) Does the object move in one direction or in both directions during the time shown?

  A certain type of aus :7piurvf2u1l h-c 55r -nguetomobile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curv fl5upn- ru5rc7give1-u2sh: e represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problem5z*pc .p:4 :twepwutxsk mf ++ (Fig. 2–35) wheuwpzt.w*+xf:s+epk : 5m 4ptcn it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object trave,bvlkz8 ,;cfeb)f80iv m pbj:3tz /e zled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the objeczhlrc q7ec rnyy r,; .dsr-74p ,omj8.t whose displacement as a function of timedyo zm;p47 ns7,r.ch ,crl8r q.je- ry is given by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of:- rof 3yfmlm;yd 2o b8iz/w3e 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 meyzob;-yf2d 3ir:/lm3wf o8object 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 interval from C to D.

  A person jumps from a fourth-story window 15.0 m abovee(d odz:k8 j/y1(cwj b a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, e /:bjd1wydoj(8(z c kFig. 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 hhwlk/*v8 toi yk1n+3 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 E*+813yk tin l hvw/khoarth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-lulp4s84 x1pyqb: uym9n u/e 6shoulder seat belt has a goony9 lp4xmup e6 :8su ulq4yb1/d chance of surviving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the rogb(t 7m91eifh ad 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 away the truck should be when he jumps down from the bridge onto the truceifb 17mt9hg (k to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions bss+1 lwi nw-z/y hauling them up on a crane and droppin+w zi/ss1nw-l g them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels abo- mcru+)z :qcrut $10^9\,km$ 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. vusbj6le ,y+i zv); an91*mdxThe front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where vx ln, )j*v+edz 9yb;ui 6msa1the 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 wq 013i zb:g )y8cbl r,b9prbkwz7+ kerater’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 p7 z8b:bwl+ p)91g krrbce,ybk0riz3qerson 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 balancdirt5 /0jyr i;8fw+ ape the average speed of a train against the distance between stops. The more stops there are, the slower the f ita p5/+ 8jwrir;yd0train’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 j4 e vo18bgn7wfall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimumwjv1 noe8g7 b4 height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfegn;s e f0/k6f f h)bfl9jii:8mr 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, 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 decelm6k /lff ;gnh8 ibf:s)if09je erates 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 trainaekz+77o3 y sypq(tlgf, 7h3b wo t88t traveling at a constant speed of 6.0 m/s Justyo o8p7az33w,qe( b 7s7k8httly+fgt 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 stone is dropped8 7s6r,pig.c3 pzsqrkki )w (f 1.50 s later. How far apart are the stones when the second one has reached a speed of kp) (prwgk6s7fs,.q8i r3czi 12.0 m/s ?    m

  A race car driver must average 200.06y8hww 9toekuo- t q38 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the lasttuqeo6 ho-3wwy98kt8 lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at7 a )pmr627 c4h9.biccz;xpa c/vvvpk7r jjl: 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . Whatvc7bcxcap7 cplj2mvv6:/.j7rrzh)4ap 9k; i 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 bo*gvpt9 qal,bu+e)ljqp030w esz2 i z3unce up one-and-a-half times higher than the second child. The init,jbq0i33 2tl e+ evgw z9luszp0q *)apial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train traveqx4judq49( 1 p vu5wxpling 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 th1d( 9vjpuq x px4uw54qe 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 * y0gx /dx,tgia speed of 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 accelxd,g/x g0iyt* eration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accel7*bpkd;6ft,3 ejnws n eration 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 inhsg ap0 )*vo+dtersection 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 od+)p0v *as hggreen. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a co0/:r0d 8m qvtp.vnx btnstant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a conn xmb:v 0/vtr8d p0qt.stant 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 b+ wkpix,sp ,d jir-88guilding; 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 thxs ,r 8kigd-pi,+ jw8pe 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 verticalloit -2+uovq7 sy up at the 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.- 2 oqvsui7+to5 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 s0oii7 5qfewh, jj06jyt x3y, take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (Ini,j t6s0fj3o 0xhyy5ji7,q e w reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers j15iio8fj rp/i8 k/y pthrough 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 88j yirokf p/pj51 i/i15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball verti* :snjcmnw .g,qtlz, )cally at a speed 1.5 times faster than Joe can. How many times higher will Bill’s bawg sn,.*:lqn cj,tz) mll go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stanm :wu79w:xrkn7orz;u ds 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 itr: wo 7uw79m :xnrku;z just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular buil/j1 r ruh-7pg;me3pr rding using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to tjp/h;p7u- 1reg rrmr 3he 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 grav7 bqqejd 9305elj55ivg hj-fp ;f3 vjph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) ;qjjv0p-55e 3be5l ivj7vgq3h9jfdf 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?