Does a car speedometer measure -u ohin2 y,tidcn3 y,3speed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, gioc(+qts1ge+jiva( *w ve exat+ie*gscov (a+qw( 1jmples.

When an object moves with constant velocity, does its average velocity during an;r qb cs*1wqeaz+x7axmrta4 )zh8il8p.x2 9 f y time interval differ from its x8e 9fac rlhs1 2iq 7pz;a *xw).qxr+tbz4a8minstantaneous velocity at any instant?

In drag racing, is it possible for the car with dd-.w5 nw ia1xthe greatest speed crossing the finish line to lose the.1-nw di 5wdxa race? Explain.

If one object has a greater speed than a secon0abxcpl1a(4m em8v-f 3zkmu3lci0vi i1 z- -kd object, does the first necessarily have a greater accelerat 0f cizmx 1-vpvz(-0 4l 13ebaul-i mc8km3kaiion? Explain, using examples.

Compare the acceleration of a motorc4negjor fbxw6,z c*48ycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from4 g,x64r* cbnfeowz 8j rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Expo jdpe.c, owpa7z (e*3lain.

Can the velocity of an object be negative when its acceleration i1:+gri y2q 8wu+tc gp-bm jsj8s positive? What about -1bgw+jytcrmij8 +p ug :sq8 2vice versa?

Give an example where both the velocity and acceleratiolp*2n oymn-(rg:4vb pn are negative.

Two cars emerge side by side from a tunnel. Car A is travelu0q9t3q+m hfring with a speed of 60km/mr +h0u9f3qqth and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If l -s t8y3vlsf4t. x7x ox9qi5a-m jb:hso, give an example. If not, explofxb83 t9h qa jl5si- yv-l7s.xt4x m:ain.

A baseball player hits a foul ball straight up into the air. It leaves the bat v- t4d fjv3i+pp, nh5h1jjq3 gwith a sp3tj13,4n5pi dhq f -vpj+ hgvjeed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happenih5nb*;+ p3cnbi eth5z ng to its acceleration due to gravity — does it increase, decrease, or stay the samincn5p 5zh;b3tbhe*+e?

How would you estimate the maximum height you could uvy. 82 nyiyvukh85 : ex+loq:throw a ball vertically upward? How would you estimate thnl:yiv v :uxoe.y + 528ukq8yhe maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed p*el9t4h b t- 5wdbs:wof Then you travel the same distance from point B to another point C, moving at a con9btplwb-:4tdh* w5es stant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0t fow7 mb87y su244yyb-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 pla7ws2bym 4 y tyu8fb47ote, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock faw-yxx6acxggc k47 6lf;*5 es ulling from a cliff, an elevator moving from the second floor to the fifth floor making sto-6a5 74 x xucs xwg;ekyl*gc6fps along the way, a dish resting on a table?

An object that is thrown vertically upward will visfy kol;m7df9r)8. f xya+ar2 b )7wreturn to its original position with the same speed as it had initially if air resistance is .)kwfrm7ds y+ yb a7xar)8vo;92lf fi 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 vel+luzbkm, )1xd1 ;j at6;lgaaqocity and nonzero acceleration at the same time? Give exmabgz;,)+tu6 l;qa1 alxj d1 kamples.

Can an object have zero acohf m:)b6zgz1 celeration and nonzero velocity at the same time? Give exampl)m bhf:z61ozges.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [bwggrc . (2qy+Hint: First try to duplicate yq cg+2. rbgw(the motion plotted by walking or moving your hand.]

Describe in words the motion of txpaej5 u+6.qh he object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 23ag3pr,abs r2 t7ed:o15 km in 3.25 h?    km/h

  A bird can fly 25 kmjz+ b( cesm j:;p3o jgt*kui(.sb7;z g/h How long does it take to fly 15 km?    h

  If you are driving along a straight rokguu sf8ou9-(ad and you look to the side for 2.0 s, how far do you travel during this u-8(ou9usg fk inattentive period?    m

  Convert 35 mi/h to b5d . m2f.0dnvd i+boz
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves froj,fal m.9nexjzrj/tl0m,(ho o7tw) ; m $x_1$ = 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 z y wruymj/74xek;1m- steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65;/ryu4 w7-ye1j mzkxm km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning flash and ts klf-qy)k +*/mrhj6ba -9ccghe following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate m9c+)*- c6 kyb/j-fagqlksrh the speed of sound in m/s from this rule.    m/s

  A person jogs eight comple;kpw pw3 y0du /l5(xcxte laps around a quarter-mile track in a total time of 12.5 min. Calculate 0c3/wlxypwp x5u k(;d
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainesv:axc1bzl e* y4)w3er in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfwa azvsc:ee3y4x)b lw 1*y 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 ea.xe,7h (w gbh pk ygj9/6+x /nslzkg/qch other on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long wi/s 796kn+.phg/qxy(jxgbwg,e kz / lhll 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 long will vjjq* oyq1 cc yj/.i;+it takey1c*;qjjq+oijyv/ c. the car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a taiex ugn-7 etqq3:z y).gu)0srwlwind that boosts its speed to 990 km/h en7ywg)u3stu xz:rqe0) -q .gfor 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) 7kwbj z b /1dpuydge1v:20b)efb3za of a complete round-trip in which the outgoing 250 km is covered at 95 km/h fo )/bvbu1z)bz 1b :2egafydp3 dkew0j7llowed 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 speed hits the pins at the en9kqndor:a o5 (qwm,z:(v7lu gd 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 qq9g:uo vr o (dzm:l75(kan,wspeed of sound is 340 m/s.    m/s

  A sports car accelerates fkl u vqi)nw xpdnl:r4:9a.5/ trom rest to 95 km/h in 6.2 s. What is its average accel:iwl dxap5v.u)q nr9 ltnk4/: eration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerate j01,:28lty ab 6gvgn,vgkpf ks from rest to 10.0 m/s in 1.35 s. What is her acceleration k21jtkygf, n8pvab0g6:v, g l
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an ac9 lr.lww )z qiuw,hv /d2)3iwvceleration of abouthi w/ lqz)3v vi9wdl,r 2)wwu. $1.6 m/s^2$ 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 spes1 kjzfmqw d 4 v8:lw,65rbza2ed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its acafz:rwlzd5qb2k6v w81jm 4s,celeration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 and moves iia3esl(xt)-nmm;o o w ty9a, 1n a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a fla,3n a- ;wm(y t)o9m o1tiesxunction 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 2ggr4.9-ywcijbm 8 l i,a.fzy s. What was its acceleration? How far did it travel in this time? i8j cfg.g9rym,i- wal 2z4b y.Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was it6ne be:o6.b.1est usus acceleration, assn6bues eo16..uste:bumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How lon.edpl1 wm6w( q7w4fzag a runway is needed if the (constant) acceleratio 4dal716q mw .wfewp(zn is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst -xybcb )(zs6imbg x3ji6j+ 4t out of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration o3)bisbj 4cx x-6yg itz(bj+m 6f 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 unifo20pam dgis-7ormly from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that time?mpdo7iag s-02    m

  In coming to a stop, al1t os7n9: rnbqgwq5n*d4 nq; car leaves skid marks 92 m long on the highway. Assuming a delo5qbsnnn1*g7n q td; 9rqw:4celeration 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 endavsd8) kl4o0e of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Exprekls40 o8dav e)ss 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 )zhh-qde*su8 of 95 km/h and human reaction th8e dzqs -h*u)ime 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 equatiord9 y3(1xatksn for the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on thno.0 plk.vnj 3e highway. The car’s driver looks for an opportunity to .jkp.3n n o0vlpass, 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*p- k) rn5xjuw3+aqz3 fmw7 dk than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. Thqj pw5*uf+kadw )33nkxr-7mz e 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 app37cxme8liosjs07.bxcb m0: b l4o0o oroaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The interl3i0om0b7moo l 0 j:e8xs7bbc.cxs4osection 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 bs)md.o0txmf) j;d)u m9.s w thelow after 3.25 s.mm o .;.mfw9)x) 0tusd)jthsd How high is the cliff?    m

  If a car rolls gentl/apmx qhe7 3;wy ($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

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

  A baseball is hit nearly straight up into the air with a speed of 22 m/s 5p 1x9u egn5n,, 1kd rgy4gdrh
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball e-hlw ,8 batr:l u/l(r3.0 s after throwing it vertically upward. With what speed did he throw it, and whatlrwh(-8, lbau:el /rt height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rr lqk)/:n 7zvc)u;x-u tg pucotj2+q3est and falls under the influence of gravity. Draw graphs of (a) its r octu2cxk/;)q7 p:- n+ujqtvulg)3 zspeed 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 odamc6xn3,yd4 pb6h; fp0m7q 5.20 m/s. At a height of 125 m above the E30d,b mmnphyd7fx64oq 6p;caarth, 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 freely93sr5m afx.px 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. See Figs. 2–18 and 25x.rp3xs9 m fa–21.

If air resistance is neglected, show (algebraically) that a ball throwni6aamje(; /n w(ahi5i vertical; (jaemhawa /in5i(i6ly upward 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 with a spee9 bftdb vc,.)ibj-: wutb)mj0d 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 num25 sit q6 *- g5myukoduq2da/i+dw+i bber of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apdqiqm*iu 5++b2 sg 6t2ydiuod5/ -ak wple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past 3vm2 bs-tj,qx *t7.v4 lo ntjbu,k7xna window 2.2 m tall (Fig. 2–32). From what height above the n-, u,btj3s4 t7nb.v2tkmjvxol7* qxtop of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean is h5e06hu3 bqcsa eard 3.2 s later. If the speesuhb 0q35e 6acd of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your gardy* v 46hsg:7hk gl7;: xqgpcfden hose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33);6dc 4 qgy7hl:shxp:gv* g k7f. 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 upwec87ji . mecr7ard with a speed of 12.0 m/s from the edge of a clifeem jc7.rc 7i8f 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 t d-jpxe p25v8pass upward by a window 28 m above the street with a vertical speed of 13 p8-jxv2 e pdt5m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of time.c ;) p:zas( pmseik/m: (a) At what time was its velocity greatest? (b) During what periods, if any:(caip;emm ps/sz):k , was the velocity 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 of time is m3q3 5.cyxoad5nzv1c plotted in Fig. 2–28. What is its instantane3 cm5azo n5dx.1yv3qc ous 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 automobilek hp,2 ervm)c, can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting ofche ,pmkv),r 2 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 acce*k5vu3 3q8o+now)i,tjx f nmqleration of the car in the previous Problem (Fig. 2–35) when it is ij3nio5) owqq3tx 8,n f+v u*mkn
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object trave n*yml*qu- g by4qk(m7led during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a q5uo6 ds(ibw .:l-mjcfunction of time is given by Fig: .oci-l(bq5um s6wd j. 2–28.

Figure 2–36 is a position versus o- 724g vgd)ms pbw.mptime 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 object positive or negative? (g) Finally, answer these same three questionsg4o2.mmgw ppvd 7bs )- for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m f4/s7 ;the mlbabove a firefighter’s safety net. The survivor stretctml/e4bh s7f ;hes 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 gravity on the Moon is about (ea*j4(u/fy qp4n b)(cjbj z vone-sixth what it is on Earth. If an object is thrown vertically upward o*f zevajbbcup 4/()jn4(y j q(n 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 mw9cab7gsp qa 416)e fseat belt has a good chance of surviving a car collision if the decelerati)4f6a1wmp9gc7 eqbsaon 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 pursu39b6j 7a+ gjtph xp:mders 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 qui9xmjtdpbp76ja g3: h +ckly 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 for front-end5slv.v6 xx2 ta collisions by hauling them up on a crane and dropping theml5s x6va.vtx2 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 ti*v9ue ))ky juravels about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from rest. The front of t 4cwcs6*tml je(0nu z;he train has a speed of 25 m/s when it passes a railway worker who is stand*zs 4t wn lcce6;u(0mjing 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 surfacp0jropq qbs7 dw528 4ce into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average d2rs 48d70 wpc5jpboqqeceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid tvfu8 rk5crs4. ransit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in t ru8.4 fv5kscrwo 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 andy( g 6o .ft, kv x8itp;lp,ifghz:;p8z free fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. I. 8fxk;h:p6yz o,t z 8g;fp(,vpt iiglf 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 a ball is planned so that thlbd0c e b;31gne ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difgb c1d0n;3b leficult 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 lp2oo5w3o*b6dv4sj 1 q fz,njtrain traveling at a constant speed of 6.0 m/s Just as q1,ozpw4v flosj23o * 65jb ndan empty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from tp39oji.: o82c1 e6b 0svikvblqtl im, he roof of a high building. A second stone is dropped 1.50 s later. How far apart are the stones wo18 m t,jl9k2ivb6vi3ib:espc loq0.hen the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.3+ijmotoj9 4as4*v 9 3thhyr z0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintaineso*43yhv zri3 +tatmj 4hjo99d for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at 18 km/h h.c v5s5 , -lmzag8xitld*r*e fzqh.6 . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration de,5sr-f 8 ia5q*6 c.hthgzxl vzl*.m (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can/g3 po2 ;o.7d1re0q im tgr+jiseqv+a bounce up one-and+.p ;iqgsamore7i0j1 r2to + g3/qdve-a-half times higher than the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train traveling vrvq9;,pi,iw otx3g23q vem(in the same direction on a track parallel to the road. If the train’s speed is 75 km/h v 2,vxo (mv 3q ,iqp3i;g9terw. 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 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 44 m/8sn9) of;h/ pnnbzb f9s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during 9zofsb n nnf/pbh8) 9;the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleratii*) j;(qerho j8 l4vwlon 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 shohr4z; 4* b4escbr ie1xwn in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are drixizc 4eb ;1b4hr4*ersving 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 c qn.dba,*6.e(ab nm rzonstant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a eba n*md(6z rnq.,b .aconstant 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 afrgs n1zl*/2s(iqcp;y ter that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones lazip ;l (nr1sg/ycq*s 2nd 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 ti*pru c5m gsh*)me. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balc)* p*uc 5hmrsgony 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-falling parachuwzv fq8x89/h qtist to fall from a plane axq9fq8zh8v/ wt 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor beljqg58vkp3k b ae2+ q( tcyprvmd6w 8*(t to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger pr(p yr qbva k86dc3582kqv+jtp*( emgw oduction (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically axy/kx p6+dm-ig7t0fmt a speed 1.5 times faster than Joe can. How many times higher will Bill’s 7pg-/m xdx60 f m+ykitball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the gro17sq0s5:lp3 gmkjpvs pq31r p und below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball qp :7 1 spk3sjgr1v3l5mqpp0s 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 o wo(/-48 zr owsr8htato find the height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fataz 8(4w/-o rowh8s orll. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B. (a,zgx dqm/ ez4jdkv* pd+g*r06 ) 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 passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous vkm06, dp4rjq/ex* zzd +g dg*velocity? (e) Which bicycle has the higher average velocity?