Does a car speedometer measure speed, vev;nu -2 ieeutchf4( ;no+ymf45e q*iqlocity, or both?

Can an object have a varying speed if its velocity is constant? If yzi2aau -g 3uy4es, give exampu yug3-iaa z24les.

When an object moves with coeb+xl * nuxw pkf1djqmw6us( +5 z..)cnstant velocity, does its average velocity during any time interval differ from its instantaneous velocity at any instant?+cxm (uw l1)xde+. ns*bwz j6puf.q5k

In drag racing, is it possiblfsi+) 1e)sn -lpb)rbxk ja*a 9e for the car with the greatest speed crossing the finish line to lose aa s)erls b)b9+p1)ikjx-* nf the race? Explain.

If one object has a gre.ba4 f vq,9cpvater speed than a second object, does the first necessarily have9v.bp,f4q cv a a greater acceleration? Explain, using examples.

Compare the acceleration of a motrl xbj(l.(t-2y06e r 1 npgh/;nddumsorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the same tidsnjy x;nru. -0l (bt h(l pg1e6r2dm/me.

Can an object have a northward velocity and a southward acceleration? Expsqnw c:kd1 j45lain.

Can the velocity of an object be negative when its accel(i2 p3.4kk/curkqcy w eration is positive? What about vic /cc2ki.ku(ypkqr 43 we versa?

Give an example where both the qahk;5zk:d kb/ q +xp8velocity and acceleration are negative.

Two cars emerge side *bq /-x9nf3 hxua0z qbby side from a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an ac q-z*nb/qf93b h0xxuaceleration 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 accelzzu1 5hk w*k/peration decreases? If so, give an example. If not, e/k*1 w 5zkhpuzxplain.

A baseball player hits a foul ball straight up into the airpme- j--k7q e1q ika1bagg73(v4gc lt . It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fas jb 7-aem-171pka3ikqeqt( vggl4cg -t will the ball be traveling when the catcher catches it?

As a freely falling objecth+y5-eq0ue na speeds up, what is happening to its acceleration due to gravity — does it increase, decrease, or stay the same+n q -e5yh0eua?

How would you estimate the maximum height fk8pg7c c0qube6 s:tj. +lq05ci;gw yyou could throw a ball vertically upward? How would you estimate the maximum speed you could gi0g8j ;qwc+sq k :l.i56cc07b pfetuygve it?

You travel from point A to point B in a car moving at a constant speed of Th ask7fli:wd 8,en 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 entiraw7ids: k,f8 le trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a ha(m 3w5twdh2kb 57gf3.0-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 the5 kw7( 32htfgmwabh5d plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleratjq9ld swtg b.4n,/wx8 9i5axrion: a rock falling from a cliff, an elevator moving from the second floor to the fif b x9sq5n9j ,grd .w/lawi4tx8th floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to itsb4oek;z;x py/ )vgtoi 594h tt original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result /y)vgxob;p4z h94tiet; o5kt 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 zerozlyk)5 wjl 0v0 velocity and nonzero acceleration at the same time? Give exa5lk v0yz wjl)0mples.

Can an object have zero acceleration and nonzero velocity at the sam9l qnxu .87esqe time? Give examples.qlq.9nx87es u

Describe in words the motion plotted in Fig. 2–28 in ty l 8 gct b7seh,ha7e.) s7x,dkuje/6aerms of v, a, etc. [Hint: First try to aklc7x8d),bjyhh . ae677gte /su,es duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object gru 2k7yfc/wdj0:l -qzdaphed in Fig. 2–29.

  What must be your car’s average speed in order)a,mm bfp+zg+ pp3,r1wsup 7 q to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it taka30hw,h o kx;je to fly 15 km?    h

  If you are driving along acz3 ; loimw.+5lwe.go straight road and you look to the side for 2.0 s, how far do you traveelowow 3 5i.;lc+z.gml during this inattentive period?    m

  Convert 35 mi/h to 0/zj wt;zkx ggt aj)7.
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves 6,vbv h:hso js+32 )ylpei4weiwng;: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 95 d*ymv v:g1mjlu;0 6vykm/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 m6vvgvjym;l *d0:1u yminutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-t9x.p 6mkv-oia humb, 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, estimate the spex.v-6kma9oi p ed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a total timi3j(ydq5t-s8roa z m0)cx( xz e of 12.5 mcxztd3mjo -(iz (a)yrq8sx5 0 in. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from itggc3c 6mgkpxaq ( k9 *s/ynn(q2: 7bwds trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back i m2y kw(x/gq *:cdcannggbk6ps( q9 37n 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. E,og7hft7 c 9ryach 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 reh,t f oyc7r9g7ach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling Hon p 2wkvr3 i/m5ko/zi+n tv.:kw long will it take thk.r+n/v3k 2pnim5w/: iov tkze car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encw +)u lu* qlkmu2d( +v oif)rwxbn4i15ounters a tailwind thatrf don1i+(4 +xlwuiluv wum)b5* kq2) boosts its speed to 990 km/h for 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 of a compx fy93 ptyg/4vlete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.tx4g 9y /3fypv0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins :zd9u usiwoud* 6y6 r,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 the speed of the ball? The speed of sound is 340 m/s. 9 wsu*ydr6d:ui, o6zu    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. Whatxw7ol ltz2 d:p3m;rl+ is its average accelel: pxr3;twl z7m2d+olration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acceleratiwrn el.p r 9*qvof2733 qipiuj/gfm(5on qr3 f qi57o2/ .n*emg lv3prpjuwf(i9
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a psmw rj p*(t*fw1p)u 1aarticular automobile is capable of an acceleration of about w)1 arfs1(pptu wj*m *$1.6 m/s^2$ 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 cofze -hemm6 zx:8 1h--w1d wswhnstant speed travels 110 m in 5.0 s. If it then brakes and comes to a stof1dh-mw w1me6-h :xh-z zes8w p in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, wo krd pkecipwfv426; .vi7;+qhich 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 vep67 p wd;q+rovk.2vk4i ic;felocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. bbr6d znc *p43 df9:ejWhat was its acceleration? How far did it travel in this time? Assume constant a:63bpd zr9bdef jnc 4*cceleration.    $m/s^2$    m

  A car slows down from 23 m/s to res) *r8k;aby4f kv., cn)fct:pw iwpp- gdwm0,et in a distance of 85 m. What was its acceleration, assumed constar*myaf., wd) w,g0:-)pwpcvkb kfcept i; 84n nt?    $m/s^2$

  A light plane must reach a speed of 33 m/pfrj)l/;r 4und1 kr r3s for takeoff. How long a runway is needed if the (con41 r3rr;prnduf lk )/jstant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst oumr+67d(bl i.t :szbmnt of the blocks to essentially top speed (of about 11.5 m/ zm6nrm7 b (l.bti:s+ds) in the first 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 of 12.0 m/s to rest.y vnq/aty zh25 /0but in 6.00 s. How far did it tyht ab/5z.q2nv y/u 0travel in that time?    m

  In coming to a stop, a car leaveskj;++i +y;yf)rgns x s skid marks 92 m long on the highway. Assuming a decel+rnyxkijs; y ) ;+s+gferation of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compresskkl,l/lh vb8.hs56i tes 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 “hll ti s6bv,h 8/k5k.lg’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 x;k+ (fc2 *2nfzhbwzca6x2ku initial speed of 95 km/h and hu(2bh zkxxf2k* fa; cunw26zc+man reaction time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping dista-s)g up t-z/w+ u5klh8 bkbl9t 65rqaznce of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s dj7*6gij y skilx -rq,;river looks for an opportunity to pass, guessing thatlr ygq6kjxjs-; i ,i7* 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. Aft:twcnw, +uy. per exactly 27.0 min, there are still 1100 m to c,nuw +.t: pwygo. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersectiyi7nar6s ku0 1yp rv/2on just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersecti7r12p y i/a vsn6ukyr0on 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. 09-r-i xlgty5xk(npu It hits the ground below after 3.25 s. How high is the cl gxr0yut(9n- lkpx5-iiff?    m

  If a car rolls gently k 4aqsz7alc2ir+j-l*e8ez h, ($v_0\,=\,0$) 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 ais ogx7x/d/ 29 exe*zlqr 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 *, cs6sw r5jlbjs99yc vertically upward. With what speed did he throw it, and what heig6 r99ccsswsj5 j y,*blht did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls undeq(58/ tphirkvr the influence of gravity. Draw graphs of (a) its speed and (b) theth 8k5 qirv(/p 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 height of 1 1knp8a-j cgtrod9g abd82(8;c ray9d25 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the grouna-addo d88b;crac9r(gn8 yp 1gjt9k2d? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled durg y/n+u*rvf s5a3 4o 2lja:njpsi,v s3ing each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.).*5 vn r2ljg o:s jasfu+p,i3yn/v as43 This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is negle *bpo2v;b4srscted, show (algebraically) that a ball thrown vertically upwas v o*b4rps;b2rd 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 vertically upward wi -yf835r4mxa lkkz0njth 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 numberf u15 tif)vx)f of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the uxf)t iu 1f)5vfnclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to tpu kh8t8vro0-p4 hzz5ravel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone fpuk or8z5 -th 4hz08pvall?    m

  A rock is dropped from a sea cliff, and the sound of/p/ w0vnh ; ej+k*lstj it striking the ocean is heard 3.2 s laterj+ nvt;lwep0hk /j*/ s. 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 hard stream o0:y muh 5e,j3/ mfg q;l8zamoff 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 the water speed as it leaves thfmg3m/,; o: y85z0ha ef ljumqe nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0bx*2dyy+wb,z ;u3;+mwz ti ht m/s from the edge of a cliff 70.0 m high (Fdt *yx +iutz+h ;wzb2mwby,; 3ig. 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 streelnqdvff 993+xt with a vertical speed of 13 m/s If the ball was d 9qfl3+fv 9xnthrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of ti/rh-u /7b3mg7llp6eaf5 d q ilme. (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 accuf3ralm - g hb/7pil6leqd57/eleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a stlzoz;by /-eou4w8h peu7 v2npw1he 8 )raight tunnel as a function of time is plotted in Fig. 2–28. What is its instantaneous veloe / eo h1ppz-wwv 8;on4l7yu 8e2b)hzucity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as shoz b2pvzp* co,7wn in the velocity–time graph of Fig. 2–35. (Thczzpp,o*v b72 e 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 th1 pxo c5-7thote previous Problem (Fig. 2–35) 1t5h-xcoop7twhen 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 object1n gir;qs3.sk2dtd i/ traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functijrez*fnw.j36 on of time is giveerj3 6*jz.nfwn by Fig. 2–28.

Figure 2–36 is a poskuk +oq g8ybms865tt5qa 1 9q ufmfh0+ition 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 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 objectqg1 kumo 9++h f8m55 0qufkbs8ttyqa6 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 w9i3).p7gee8*itm yxxqch 3 vqindow 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before commx3h.e9 8tip*yx v)37 gqiqec ing 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 gravity on the Moomo69(u; *79pxg+foh q ;q*ngvqct fojn is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initih6mg 9+c*qg;qo7 (*v pjf oxo9tfuq n;al velocity?

  A person who is properly constrained by an over-the-shoulder sbc22p2l ko5d beat belt has a good chance of surviving a car collis ld52bp 2cokb2ion 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 pursuermd9z/bt9 y) bes are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by kb9med)9t z/ bynowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars bej;u+v(g f3mfor front-end collisions by hauling them up on a craneujbeg v(;+ mf3 and dropping 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 cey o 0beqkr.e2y8qrpo vy10.ddg 37-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 acceleratiu+xagew v+8wbkfj,uj8 2): gxon from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from x8x gg +k+uwjjw )eua ,8:vb2fwhere the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.-2s avexj/p 7e0 m above the water’s surface into a deep pool. The person’s dowa e se2j/-xp7vnward motion stops 2.0 m below the surface of 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 necessary to balance the kcg0 n+(e.qgh x5xm* raverage speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. Tox +( kh0cgg*qern5 .xm get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fisho*mckx pwb3 +n e;)gl-b2ye hk 6l7( 8s)kzpqb. Suppose a pelican starts its dive from a heig(b 2h*kzn3b-ew;y6lxo)+lk p) bk cgms8q7ep ht of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes,rh)g/1qtf qee ek 2.i a ball is planned so that the ball will stop within some small distance of the cup, say, ,q i)fgert.qe k2 /h1e1.0 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 constan0yykd g-azqeoz.:l :x:m;)xu t speed of 6.0 m/s Just as an empty box car passesq: azxu:-) y;zl:g mkx.eyod 0 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 sewfe( xul7rnmh6:xd16qviq x-p9p, ) ycond stone is dropped 1.50 s later. How far apart are the stones when the s w -(xqhx nfpyv:pq96udl1 er6)m7xi,econd one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the c;yuzab/t y1uyf2+g:aqv( v l lik6* 0jourse 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 last layty/;kqya 1vl *z2uvu6+ja:ligb 0 f(p?    km/h

  A bicyclist in the Tour de France crests a moun/xa p.5lh t, ,tg:lpy:qwvoj :tain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, hip,5. :otyg :jxalqp / t:,lvhws speed is 75 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 thh58ods ,1u )hcpt9 rhe 1dve4rampolines. The first child can bounce up one-and-a-half times higher than the second child. The initiaort h8hp9 cesh1 ,1ehud45) dvl 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 overtakes0+ g w9tticc-t 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 time0-tiwcgt ct+ 9? 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 thppe7k.h-y viqs2j j 16;wwm .krows a baseball with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacementkj. w;pm hqp.6k e12yw- vsij7 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 recsu+ia ek)i:+- lbt- nst, with an acceleration 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 i736 bclwd nw 9:ugugr6ntersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When 7u9 :6bgdc3 u wwlg6nryou are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder trloi +gre)+g5(.e giaxaveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constan(a ) o+ii.lrggxg5+ee t 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 roofz awe;cb4k+(f of a building; 2.00 s after that, a second stone is t+ezwa bk f4;(chrown straight down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown ve9(ld.*o(/ m kp) pw dhhw8qupjrtically up at the same time. The first stone is thrown with an .hd(p8 /pm wpwdk( *9jhol)qu initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be 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, hobty3 th4*mzr t;z 6a-i2clabq:dux*1w long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will 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 r q 6 cuiy4t*at;td1:xm3b b* azl2h-z.)
   s
   km/h

  A fast-food restaurant uses a zebfhbp9 nu6 xa5+t* hy*d8u7 conveyor 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 fa h*ub8f+d6 5a7 ybnzt9hpue*xst must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Jp:chugd d qn+:p:, -tcoe can. How many times hic c:-dn h ptgqu+dp::,gher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff w:o/z wduox ..thile your friend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the balltu/ .:dwxo.oz 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 find the height of a particular building using a9k9effs0au+ebrim*l* n- g3s 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 re +br *k *sfal09gmife3 se-u9nports 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 graz cq6q(ie.w/o ph 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 acceleration? (c) At which instant(s) are the bicycles passic6w oq./ (zqeing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?