Does a car speedometer measure speed, velocity,q p, 90pe1x ii;f7alpj8hxu 8j or both?

Can an object have a varyinyywi69tv8:1v3 ;oa x jmkdyh /h*sc/c g speed if its velocity is constant? If yes, give examples.a;3*/sikcdyv y :/x m 9hoh1vwj86tcy

When an object moves with constant velocity, doed 6agq 5*a8s1kaur8ptk5y :oqs its average velocity during any time interval differ from its instantaa a g8:qk5kup8d5ra 1yq*st6oneous velocity at any instant?

In drag racing, is it possible for the car with the greatest ff+vxolx:hh jfj);/o ihdg l2:y9s:;speed crossing the finish line to lose the race? lx:y2 osv/) j:+h j: ; 9ohif;fdhlfgxExplain.

If one object has a greatezea- gwdw a;4 ufu04,kr speed than a second object, does the first necessarily have a greater acceleration? Explain agf0uw;u4w,edzk -a4 , using examples.

Compare the acceleration of a motorcycle t(iuyis)*1i/jgnki 5k w8b p z- +9mulxhat accelerates from 80km/h to 90km/h with the acceleration uu nw9( ism*ii l) j+85g-xkkyi1zpb/ of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity aw/vk ym642 +f5y 27meyimi mjznd a southward acceleration? Explain.

Can the velocity of an object be negative when its acqpxsw/n)5 pr)8 +mthm celeration is positive? What about vice versa?/ p q)sm5)pntwhmr+x8

Give an example where both the velocity and acceleration are negra8mcf2:qqr4 p,nt)+ rm ylj;ative.

Two cars emerge side by side from a tunnel. Car A is traveling with a speed 2 1t4v)l,,wi pewpc,i3ob f:k( sebeiof 60km/h and has an acceleration of 40km/h/min . Car B has a speed is3b 14,(v,pcfpebe): w,o2ieitw l kof 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 decrknz2jif c o79g*c *nfxle*67 +jwrf -keases? If so, give an example. If not, explain.r*jo27 *f+n l*k fji6gce97 cz-nkx wf

A baseball player hits a foul ball str 3w.;o8qrs gtwy3) j hkt;4ndyaight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher caty .3k)s;h 4wtn; rq3wgjydot8ches it?

As a freely falling object speeds up, what is happening to v0g z54/pm8c lqeh+i dits acceleration due to gravity — does it increase, decrease, or s5 gd0cv/+imq h4lp z8etay the same?

How would you estimate the maximum he(va2 ru8z*cesu-oz3 x,dk7s m3(pvr yight you could throw a ball vertically upward? How would you estimate y v3sz-zp7dom,rus2ke*uva(3 x8 c(r the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed of +th5 -tb eia7lx rtf+g9rli4 31*v zbe 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 t b3axrt7le1b5-v9lr4hf++ zteti i *ghe entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical strio.if 5t qfvjsal a.9(+ng 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 wilqifj at+oafv5( l.s. 9l not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock p9w euxy i,4v*+h ,ca4ic9jeqfalling from a cliff, an elevator moving from the second floor to the fifth floor making stops along 4cvj9 phc,+ xa weue ii*94q,ythe way, a dish resting on a table?

An object that is thrown vertica o 55 ;w*)wrvdgxgogc;lly upward will return to its original position with the sac5v;o)o;* rg5wgxgdw me 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 opposite to the motion.]

Can an object have zero velocity and nonzero acceleratu,*rvb+ pydx4ikf:no ( 6s/quion at the same time? Give exv s*y+p6ixd/n:( rfq,ou 4ubkamples.

Can an object have zero accelerbl 2ea jj/uf..pt8daydy21e7ation and nonzero velocity at the same time? Givea1p /yjtyedl2u7jd e f.82.ab examples.

Describe in words the motion plotted in Fig./9mh8ibd.vp, gvi. q n.dk -u3ii.ing 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by8.v-nm i nd.ui.i3gq,h 9ibkvi.d/g p walking or moving your hand.]

Describe in words the motion of the object graphed in Fdg:/)sh l+ pjhig. 2–29.

  What must be your car’s average speed in order to travel 235 qo+ at +u6p6)z:6ut km/b1uk knz9ljdkm in 3.25 h?    km/h

  A bird can fly 25 km/h How long does5ju jykwh ec1po/i 36* it take to fly 15 km?    h

  If you are driving w ge nf xh a43013ljxz- 89-dmfuzq*ik along a straight road and you look to the side for 2.0 s, howg1zhjw9k0e*- af l8x mqzn -iu33f dx4 far do you travel during this inattentive period?    m

  Convert 35 mi/h to *cb -p qja)75,zi n-tm/xt,qmz wwq y2
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from *w g )uxry,naqw t)3.a$x_1$ = 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 steadi vugl6h 3*:jwgmk/ uh6ly at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home v hwmg/u 3 6:gu*6klhjafter driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning flash and4;r :9)nja a/,vxxyic)durab . jfb;m the following thunder gives the distance to the flash in miles. Assuming that the flash of ligh)4af: v.xr b)bai/ax y j9m,dj; nrcu;t arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around 4n 8qmv*.wawl a quarter-mile track in a total time of wmva .w4*nql8 12.5 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, 4 zm(hb94e c *lkbjg fkt12f-zmoving 116 m away in 14.0 s. It then turns abruptly and gallo*k-m21zkhfe gztj(9 4 4bb flcps 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 approaqac) 6(a o;l lujlb/)lch each other on parallel tracks. Each has a speed of 95 km/h with respect to aol)j)l;llqa( u6/cb the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling Ha3:k+ 9t grcblg 4nd)uow long will it take the car to reach the trubglukd)94 +cg3 rtan :ck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encos/k 2r*fv ay4win j7hi(l4 g 99/1dgqij sirs6unters a tailwind that boosts its speed to 990 km/h for the nd2 rj4/nsq97isaw 4(jgk/ f1g6h li9 ii* rsvyext 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 complete round-trip inp h n8/ybv5m wilw5yxn,1:zp c07 :jgm which the outgoing 250 km is covered az:, nclmjivb/ymwp :5yh5xn8 0p 1gw7t 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 s+zc :p-kyg*a9au)k p6vw8 lwwpeed hits the pins at the end of a bowling lane 16.5 m 6w-:p9wkcguaklz+p*a vwy ) 8long. 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. Whdgx;ymfhm 0:b5 ho:e:at is its average acceleration:h0 xm b ohmdfeg;y:5: in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest tktrh/syek. k0put )1* *glw w5o 10.0 m/s in 1.35 s. What is her acceleration*s510h.* )gpkktut / wrew lyk
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is j1ymukm4sj9d3a/aqeu 6a 1ep/2 sw5ucapable of an acceleration of abou12y a6d1km3/japusu ae/95ju mes4wq t $1.6 m/s^2$ 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 5k* mwtaf0mk2 nnf pd3+v)9g.:yo;o6gzql s nm in 5.0 s. If it then brakes and comes to a stop in 4.0 ;k:.0)glzf25fv6anm q*w+9nn m kd s gotyop3s, 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 cwf 1,w5i)debb ar, which 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 velocity and (b) its acceleration as a function of time. Display each in a Tableww),5 ibd1eb f and on a graph.

  A car accelerates from 13 m/s to 25 m/silz xz7e f). zmp+ym27 in 6.0 s. What was its acceleration? How far did it travel in this time? Assume consta ipxy l2)+zmem.z 77fznt acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distat l l(tj+fe8j0nce of 85 m. What was its acceleration, assumed constae0(lflj+ jtt8nt?    $m/s^2$

  A light plane must reach a speed ozs dr ,k83)*zcgi7+tn3 usqtdff( g ymyt0/1of 33 m/s for takeoff. How long a runway is neededyu* s0so1 tyz kfg,+z(i rtc7dm/fgndt)338q if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top s1 ofevegmle j8128ez,2uq2k8yhuib , peed (of about 11.5 m/s) in the first 15.0 m of the race. Wh2 y18,1h zl22,8bmuqk ifov8jg ueeeeat 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 frg qyh0h)plw))om a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that qlgp0)h))hw y time?    m

  In coming to a stop, a car leaves s3 4w3gizd4ok0goz z3ykid marks 92 m long on the highway. Assuming a deceleration 3z 3z0ogw4k3oi4yd gz 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 )ks :ja0 u6bpwfront end of the car compresses and the driveu)jspb0aw6k: r 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’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 anjh8* akm-+qb3wi/zlz/ lglvio 2x4w4 initial speed of 95 km/h and 4w/ lw3/g8qizhojvlk l b+z *m-x4a2ihuman reaction time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stx8yh rvar50w4kfm)eqy 4iq:2 opping 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 mj0 g5bo 3 *buafc.nkn4/s on the highway. The car’s driver looks for an opportu*ck u5g o nfjan.3bb40nity 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 7 p)dy:g0uobgthan 30.0 min. After exactly 27.0 ming07 y:dou)pbg, there are still 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 f8 p;hhnt0v;9d5o c)*oxh vql car at 45 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should c)5hfv;h d0v;nq8o9x ptolh *she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground belo2z 1nve1.qcgvv fq08zw after 3.25 s. How high is the clif.0vfen v1v1g 2qqz c8zf?    m

  If a car rolls gently t+4ohm2 6 a9bv3ofvrt($v_0\,=\,0$) 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 stra tmo -gfjcs+f-g9+4 aaight 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 after throwing it vertically upward. With what 3f :cks;hm n ,6rgkr.dern:u5 speed did he throw it, agc s5u:m e3d.rkrnn ,h:fr;k6 nd what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw gnt s*1v x 0 9ztub ;ax*wn2u;k)pl0ouhraphs of (9lb )uut xu;ts*1 p0*z v2 nxh0aw;nkoa) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a hei9w2e 6m 3c* qf23lfc6p dap:dt, akccqght of 125 m above the Earth, a package is dropped from a window. Hq9km6*e:aw2ctd ccl33 , 6fpqpafdc2 ow 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 fallinwjm-bq4c*nybs,u8+ c2*);i e uhh akg g freely from rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. s c+qunijh),m *8u-w* b2kgy4aeb ;hcSee Figs. 2–18 and 2–21.

If air resistance is neglected, show (alggr:gw 4qigb8:ebraically) that a ball thrown vertically up ::q4irw8gggb ward with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertqivu i8eh*)u/ically upward with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time betw0alb66lq6q zmtgdw1f-2;cu cl o+u ( oeen each photoflash 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, butt;6o -l6ofcamwz2qbcgu+q dllu6( 01 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–/e2 ( oy7alqmd32). From what height above the top of the window did the stone fall?lo 7d2m(/ayeq    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocq4p:g6kn iz0dp) ye5 yean is heard 3.2 d 0) pqykng:p4zei56ys later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a har k k1v; 8rub2hsxe3lj2d 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 verticau1vl kh;b2 kr8e s3j2xl, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of xal sb)u9*4y*lx5sil 12.0 m/s from the edge of a cbl)iux*lxasl*54 sy 9liff 70.0 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 upwardw.tad5dvc-zaq;z2 -vju 1:g c by a window 28 m above the street with a vertical speed of 13ut .;2gj:vcz5-a a1 vc-d zqwd 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 4bxa-dd( vdd5ljeou34 ;.tw8qfy p3s of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) ydvu.-53 84 ofl4 pwb3dda(tsedqx;jDuring what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight t(s3 gc8pa/9 ux+ njevounnel as a function of time is plotted in Fig. 2–28. What is its instantas (e+u vpcnj9oagx/ 38neous 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 appriknm hg;1s96 nd 6pzf8oximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gearsmk9 si 6f8z6hpd ;nn1g.)
(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 of3 btj*u xlb)qx5+-rdev)t* gim 0gl3w the car in the previous Problem (Fig. 2–35) when it is inul +*m)x b-v)*g el3tg5xq wjrd3tib 0
(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, estimatw +wm)tu6 .wdte the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t gt 2 ;84kzmiu.wfvuww s ++fb3eraph for the object whose displacement as a function of time is given by t iwes2zu43w.8kf+b;w u+mvf Fig. 2–28.

Figure 2–36 is a positikxo1:dk4 uinzog471q y 9v 1dion versus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the4 kkd4yi1xi g nvz d7o1o:9q1u 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 interval from C to D.

  A person jumps from a d ;)ihh:ybo s3fourth-story window 15.0 m above a firefighter’s safety neyb3):hsd;i ho t. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to graviingbmctg,tz3xdm67 x ;3 r z)(ty on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many timesitzdm zxr)33 g ;b(7nxmtc ,6g higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat bel,7 dnn +op,faut has a goo f7+nnu a,op,dd 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 road below, and his pursueroev 3v rkt;n76oz l94js 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 fromo ;et j4r7nvl9z6k o3v the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions by haulingy e/vcxb (lvc* /m,ks vq/gjy54d 3sf* them up on a crane and dropping them from a certailv xd/(cbem3 **4qjsyg sy,c// vkv5 fn 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 aboz0 2mia+/vmnput $10^9\,km$ 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 front vdd)l)sj*kf d8ka2 h: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 t sdhda8 )kdlfv)2jk*:rain 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 db:ddct6qft208r(d ny iving board 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface ofyt6 (d0 dd tq2f8ncrb: the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is nece;q(rfx 5, v hcn1uvnd9ssary 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 situv(q5 n1fxnr9vu ,c dh;ations:
(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. Ssm,wxonh+o6j5rm+l 0 uppose 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 ml+xw,rns6m0 o j o+h5must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so yb4 mt)j*v2wd that the ball will stop within so4 v2wj*t bm)ydme 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 traveli 5yadholm mfw2v f/:1a73nqe 7ng at a constant speed of 6.0 m/s Just as an empty /q523lmf eavofd7 hy:7mn1wabox 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 b ac o xcmc;d;7:zz wua)8:0x8lqxjf9second stone is dropped 1.50 s later. How far apart are the stones when the second one has ro7x a9 lc)0:z8d; :8 xmcxbf;uzwcj qaeached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h rmwn: ;dzaj( t4y pw86over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed w8:6rmdyjap4nwzt ( ;must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mouke9 pnh8 wx)b.ntain 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 accelerakpb )w.89nh extion (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing ihbx0qo l4ww,d0m6j*on two trampolines. The first child can bounce up one-and-a-half times higher than the second child. The initial speed up of the second child isho0,wqmx4dj 60w* ibl $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/h7jn(m bn/wm8 at65ahrs:y5xax ,- n ql overtakes 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 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 6n:ryj (57x/b8hsxqt,a- ma mnn awl5car 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 witqk:v 7 tq kfx,q;fm7q;h a speed of 44 m/s In throwing the basebalkfx7q;qq ;:v,fqt k7 ml, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accele2qjf0 v. vr0za-ix v 16eos:(wsmq*r iration 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. Ea o3,xqn7sla9zcz8 /dbch intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s esda z x,7lo398c/q nbzach.
(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 bp 017(ce ac6o; *miopht + lwyg.k*rjby a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaininj pgbhkc*+.wl ;or0*tmcyie761a( po g a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a second st lzbaiw.i hlj/ycs* p;)8,,jtone is thrown straight down with an initial speed of 25.0 m/s and the tsahjy.b8)* l,, /;cpijwt l izwo stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone is throwb;-g5imq tb,s n with an initial velocit5q i-,;sb bmgty 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-falb )in*o,4zksg- g f0hdling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrgi0-)bk,fh d*s4n zgoict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the buxwy,c, 1*e .u. vpel hr*iehy+rgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If thepvy*c.,.+ ieyr, xe e1lh*hwu 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 speed 1.5 times faster thafj q5s ls ck9lvf2-0.kn Joe can. How many tim5s qk0 2.cfkl-sjfl v9es 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 on the ground below you:gg/hnl2i3 nf . You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw ng :3hlfni2g /the ball?    m/s

  Two students are asked to find the height of a particular bu b9g 44umlde:wr g0f1hilding 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 fal fdl:0wgr9ehu44m1gbl 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. tlwxjwo*6xph u(2 cyz*tv6 ( epnla62 +ime graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger accelerati((w txuw opl+cl62 px j*y*h2a6ve6z non? (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?