Does a car speedometer measuryn680iric aj 8/jp* :0oagpuc e speed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes .;ve9 wa5cniz, give examp5 9nz.cawev;iles.

When an object moves wikdizo3s; b( ruqvp;k 7 e9;3bdk2*vsith constant velocity, does its average velocity during any time interval differ from its instao*s;3v k2zb i9sup kvb (k;;q7di e3drntaneous velocity at any instant?

In drag racing, is it possible for the cvd o 3uyn1;+w r6p d8re1g1pzyar with the greatest speed crossing the finish line to lose the race? Explainp ye1or8r3 1d ;vzydpg+u6 w1n.

If one object has a greater speed than a second obj 0he ae+cyl- m 7f-;-fa)yzsumect, does the first necessarily have a greater acceleration? Expu7+e0 sm)- yemz;- cy-lf hfaalain, using examples.

Compare the acceleration of a mothbr-vf o(nr3t49 ,qme orcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates er hq f9v4-rbmtno3,( from rest to 10km/h in the same time.

Can an object have a northward vxvxwb *fw pz-u.*x0+ +ib7hmgelocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acce/t32 jsgxujpb9 0dl6eleration is positive? What about vice 6x2t dg/ e3jlp9us0jbversa?

Give an example where both the velocity and acceleration ar * 3e2ar( kp7js6w,pjs2edf hde negative.

Two cars emerge side by side fr**uvhat: yzf 8om 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 acceleration of 60km/h/min . Which car it*hv :au* fz8ys passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing i4 bo/r.bc(f5byf faw+n speed as its acceleration decreases? If so, give an example. If not, exp bc4owbf . 5f+bf(ya/rlain.

A baseball player hits a foul ball straight up into the air. It leaves 75mhjv/+p gkvbu45/v mfe9mrthe bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball+m74 kmf/e5rvbuph5/9 vjgmv be traveling when the catcher catches it?

As a freely falling (c4yhngv+ lh0object speeds up, what is happening to its acceleration due to gravity — does it increase, decrease4( gchlyv+nh0 , or stay the same?

How would you estimate the ma fve7.we (m/sg)7mrvk leyu7 2ximum height you could throw a ball vertically upward? How would kg )u2eyw/v7vm(7mfre. l7e syou estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a consbyq *( ; zzco:*/ vd.ybchgv5ctant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or whh *dc;qzo*y c 5yz(cb/vbgv:.y not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolti 6-wdeodr5,5+ riyqvs 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? Ww 6d +-5ydr5vi e,oirqill 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 motjdmx8 qr ,cb( hyx)((tions is not at constant acceleration: a rock falling from a cliff, an elevator mmxc(,j(qh dr( byxt)8oving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upwardu4ds1ejd (a h (zi4+ ;*wbgkiz will return to its original position with the same speed as it had initially if air resistance is negligible. I1j (kh zdz+;awi ge(4*du4isbf 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 acceleration at the samey3xzqejzu6 - 3 time? Give exampx6- zj uqz33eyles.

Can an object have zero a g81a4px r+q 1bzrhmb+cceleration and nonzero velocity at the same time? Give exampleg 1+bb+ xm8p4rqa 1rhzs.

Describe in words the motio nq3c jdi8) d0lt;( pibg(* aaeai7xd8n plotted in Fig. 2–28 in terms of v, a, etc. [Hint: Firstaaid7i(a )c8n8 tb0ixg (eddj;* 3pql try to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–2942sym p4w bu3q.

  What must be your car’s average speed in order to tra6; sot1 2k-3pmtrzcz o4t 1dly ace.et53f+j avel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h i mhm7;cvmq9ustv8- nu*8 nu 2How long does it take to fly 15 km?    h

  If you are driving ae *af(rww br6hym2*m )long a straight road and you look to the side for 2.0 s, how ff6* mh wmr 2*(b)waeyrar do you travel during this inattentive period?    m

  Convert 35 mi/h to )u/pvs12 gysc
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fr0g7q ,dqkmx h 6vr/e6j, nymj9om $x_1$ = 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 y0)suzqrcm7c xnm-s z-- jv 88begins to rain and you slow to 65 km/h You arrive h0mr8 sq7nc-)m- zz juvy8 x-scome after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five 1vgz)cqz y- l,ocy67 eseconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentialo gcyv,)e qly6zz-7 1cly no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile t hy g9f47o18*9z prth3uw42bygc mjr grack in a total time of 12.5 min. Calculate gpr81m u yz7*g ghw939bf roc2th44j y
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straigh:1 vs.+p7jj8kzgalmwj8 pj f7t line, moving 116 m away in 14.0 s. + fjz jwl1v.: 8pj jspgk787amIt then turns abruptly and gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach xa0246 sxfig 9rty+q1tic;xteach other on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initia0tt f6a;iq rigtxcx+41ys 92xlly 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 How lwx*k ,jvd ajp3h(k4s)ong will it take pw,jaj kk4 v(3 x*hds)the car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , aas + wok7,q bz(c.bzi2nd then encounters a tailwind that boosts i ckzw oi (bz,.7q+asb2ts 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 velocikjt9:4nhr mq+-u h d bko+qq2nbj.4v+ty of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed byqb4m+b qd:u.hh-tonvj+n 4r2k+9 qjk 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 speed hits the pins at the end of a bow:e2vh(z o*xzzxar4: oling 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. r: zo4vazexxzo:h 2( *    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is)ypt- md ; phqsvi-8b:g*2fx x its average accelhp q8;t2: )-xpsgvb i-* ydfmxeration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest tb lgd,8qncs8ihl;l2 ,o 10.0 m/s in 1.35 s. What is her acceleration,lc,gn;2l8sd8 blqi h
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particuld*b8vw+j 8qqv ar automobile is capable of an acceleration of aboutqw8 db8vjv q*+ $1.6 m/s^2$ 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 traveumo aryutic,;gbqh -x. 3m181m,j m- uls 110 m in 5.0 s. If it then brakes and comes to a stjc,m3q.am8 m, mu-o -hbur1uxgyi1 ; top in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which sthdtb*8dn30r t kaks;+l, ed-xoi1 1qkarts 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 Table atd1-q x k3rs b18niokl dhde+;t0k,a*nd on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceleration? How k9qqd2zqj8 m2 far didj 2qq89k2zmdq it 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 w.z1g +t8e dsr-a8 bpcc4zyw6 las its acceleration, assumyla 6c1 czt +se-8gbdpzw84.red constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. e).p2 *bb ehdyHow long a runway is needed if the (constant) ac)b*2 dehe .ybpceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed (5rv bww*b: 2siof about 11.5 m/s) in the first 15.0 m of the race. What is the average acb:svb* r2w5wiceleration 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. 2vhrx87 mk7b eh:kpej/68bh re*/pastg6 rw from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel r w 8 /kgme/* khp7:xb67hb8.p 2a6 eesthvrjrin that time?    m

  In coming to a stop, a car leaves skid mat9pkw (nu0x wd3qs*: suy s0n ol8q,u,rks 92 m long on the highway. Assuming k0(so8 0s,x: ydn ,pqtu qlwuu3wn*9s a deceleration 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 compre 8upt-j qithpo0,h4k/sses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver dur ,8hhpo04q jktut/p-i ing 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 initial speed o ;zc,hn-i8cymf 95 km/h and human r cihzy-;,8 mcneaction 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 distance of a gcj7*- m);pi1nvsy ntcar 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.c,gk rm/dbx9p08fge 9 The car’s driver looks for an opportunity to pascg9de/p f gkb9m0r,x8 s, 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- 1q1znozfub, +m run in less than 30.0 min. After exactly 27.0 min+uqb1 ,1z nfoz, 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 car at 45 km/h approaches an intezaclvpi96e ./rsection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turclzi.v p/a69ens 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 cliffu8i *a8qo48d ldyge7g . It hits the ground below after 3.25 s. How high is the cliff?888gqd*74eiya u dogl    m

  If a car rolls gently (f gvt-b; thzo zc+e+,4$v_0\,=\,0$) 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 8q802 y bo47yvhrdk dnair 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 vertyeahm6 m ; d)da:;rrjmk(4rl6ically upward. With what speed did he throw it, and what hee( )h;m66 raa4krr:;d dlmmyjight did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence opvw fg2k2;6xrl3ox:d f gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore airlr:fog22;kdxv p 6w3x resistance.

A helicopter is ascending vb vml7fprx83n c5q(q5ertically with a speed of 5.20 m/s. At a height of 125 m above tn5p f8q3vx q57mlcb r(he Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled ea3 gznbyp ,zo/c4 9/yduring each successive secon3p9oyczzey/b/,4 ng a d increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show w.m0*weh5 jplkde-5 t(algebraically) that a ball thrown vertically upward wie.wm 5-d0p5l*kjhw teth a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 1wy9ne49ce x 8 so;rx.z8.0 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 appp.)ft/) pu tth,b.u kzle in Fig. 2–18 (or number of ph pf.)p,/ )khb.t tztuuotoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travun1:v ja 8dexk1hv8 )zel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window dida88zku h1xvdn1e:j )v the stone fall?    m

  A rock is dropped from a skj:cvp y ;bcr dymb+j21a2 k.0ea cliff, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s ,bd20m p:y +ay2 kr j.ckvbc1;j how high is the cliff? H =    m

  Suppose you adjust your garden qbo z(b46lz0ehose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m aboveo60lz4b( qbz e 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 the nozzle?    m/s

  A stone is thrown vertically upward with a fi5gp1l b:t7 xspeed of 12.0 m/s from the edge of a cliff 70.0 mlbftip71:g 5x high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above )85 /*a krhd4 kmowzqrthe street with a vertical speed of 13 m/s Ifdawrq8k5zr) ok 4h/*m 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+ vqt5bth-uyq*+ri 9)3 eijke of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocityk+eqtbqyrjt53 *)iu i+e h-9v constant? (c) During 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 tunnel as a function oszg8k 1u b.,7u 5sknhuf time is plotted in Fig. 2–28. What is its instanuk ukb g,71n .uz85sshtaneous 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 accelerateex8 d a+shpbq9k(wh7:q4o s+i2w bey; approximately as shown in the velocity–time graph of Figwba98doqe7h i+4sebx : yq+p( shwk;2. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problem (Figj,u89j ew;ddh . 2–35) when ,h;8j d9edw juit 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 distj1a f2 , r.p hzzk)+lxia-lfy.ance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functpe;8 z2h+lek n*l/ld9fmb d(vion of time is l(m;l+el bekn*f/ hzdp8 9 v2dgiven by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an object ad9pqz*jck)( 4zne , ly(wakiv26zo9nlong the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer tc29 (a*6e )9z(zjkl4, wyovqnnk ipdzhese same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’s safety ne.;x*g a5eor xccpl)5ut. The survivor stretches the netecxr*o c 55l) ;ugx.pa 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 gravity on the Moon is about one-sixth wha )ubik4vzqo16 t it is on Earth. Ifo1zu 4)6kbvq i an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has a goorrk 3o21c cq2xp))bno 0ciev0 d chance of surviving2c)oq0i o3c1x cb nr 0rkvep2) 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 g3p zkt:k -1xzon a bridge, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbg3x1-t zkz kp:ed 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 truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars fowha.w he u/r- 7/:oe3(+ejp0zrwyntqr front-end collisions by hauling them up on a crane and dropping them from a certaa y :u roj.h0ph+ we/rwz3new-/e(q t7in 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 tr grarq p3-4nqw +l4tjwvi *:.vavels 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 acc i)b-o ./3zse/b mp-1lfuqwyg eleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who.se)p /y 3bu 1z-m-wfbo q/lgi is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s sur +2xl9yaiu5acpzd) ae*o 08iuface into a deep pool. The person’s downward motion stops 2.0 m below the surface of th09l2up*ed au izoia)x5c y8+ae 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 tra/l 9s,vxe qql7nsit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. T7qs,vll9x/ q eo 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 whe8 nzenh1,o k9tw.-g sfn 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 minimum height 8ote,nw9gzf nk s. -h1must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force witkg,m)cs*7z mw aql 4 :iolgjq3axk3)9h which a golfer 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 (t:xkm)lim9lzk a jqo3 7sgw3)c,*aqg4hat 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 travel6/ i x;qcxn;es;q5jqv ing at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest andjex5xq;n/q; scq iv6 ; 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 b g- xuby b7b6mdn5,m /u,k/wpvuilding. A second stone is dropped 1.50 s later. Hu 7wv, b/ky mb-xmnp6gb/5d ,uow far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial lastindxuhb2h bt5 r;imskoy5v96;7g ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the lambuox7ybhr vi2k5t9h d;s;65st lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he mo3)q:tjnb -uxu ves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his jtuqu)3:b nx-average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first nofhj/ qp,q3s40/7vol ct) kzchild can bounce up one-and-a-half times higher than the second child. The initial speed up of the secondf7qn0 /v z/3lo q)sjho4k,tpc 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 t8pmyyrq 3o v.4s: 1s+dzopuo ;rain 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+pmp8q1y y. ouod ; :rzsvo3s4 it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 4jgd,v 2z -rti7a.x6p+ fy6gsl4 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 tjvgp , -axltsd 67.zyrif+g 62he average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accea3rl )e1hwdt6leration 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 pattkco3o5qh n1zw +6/n maern shown in Fig. 2–42. Each intersection has a traffic sigqa5zw o hcm16n+on k/3nal, 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 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 constaa ztwe6 c;d 0qkqtp(/d.5 j3iont 120 km/h takes off in hot pursuejz.wt ;cit3o50(qp6d qdk/ait. The police officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building;a :::n il qcpe6kd(fc( 2.00 s after that, a second stone is thrown straight down with an initialc((li :ecnk: fadpq 6: 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 vertically up at the same time. Themul1vegn)we .0 ga fi5e4x l9 )(g8gko first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocitongg ( ei 5m9ek)0glxg)weu8al1vf .4y 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-falliega7len g(8jc95* j ep5yr; aong parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her spela5g5;97j8(rn*c gajep eeoy ed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyorsv 4xk qe:*r1m belt to send the burgers through a grilling mar*qe v:4 1mxkschine. 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 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 Joe cae9m 4s6 4q4fvtdk co1pn. How many times higher will Bill’s ball g6f 49 mp4ovt1k qced4so than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground by+:qdabaq . +zt tbn4 k;qi0.yelow you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your y;za0b +i qtqb aytdkq4 .+.:nfriend 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 o4 i:e+oo0 wiuuf a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0. 4ioou0i+ue:w3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B.;r pf-zz:0lo q (a) Is there any instant at whichfro; qzz :lp-0 the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?