Does a car speedometer 3x3ka j 1ejk xz;k9o g(og/fn9measure speed, velocity, or both?

Can an object have a varying speed if its velocity is consv,) wmgypgqy r )g4 bq8co-+h+tant? If yes, give examplesqhm+c +yw8 ogbq, -rv))pgy g4.

When an object moves with constanv0 y,;dix;ivw a7, k)e+e3wr.fdohn nt velocity, does its average velocity during any time innxe 3,wvwidifrvde.+n;k 0,7 ; yoha)terval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossing.qc+ r7icpr;zu:mib . the f zum:brqc i7p .;.cr+iinish line to lose the race? Explain.

If one object has a greater speed than a second object, does the first necessar wz)lx sf(dl q11hhz,.ily have a greater acceleratiofh1q(xhlz s, .l)d wz1n? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates n.4w,uwys/ o-0r tg .zk7 kxqofrom 80km/h to 90km/h with the accelerao g-,qwt.4 0/nuky7szk.wo rx tion of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Explain.4f 8xo lcej5orculu931fq /d9

Can the velocity of an object be negative when its acceleration is positiezk:a+m o m ev-4isskseow 9ni:6(* m-ve? What about vice versa?ai w :mme:6o -vkz*+ eiso9nsk(-e4 sm

Give an example where both te o o8mpgn* 0ll/d-rgk0)y+ayhe velocity and acceleration are negative.

Two cars emerge side by side 6w4p om.t34mom2vix m from a tunnel. Car A is traveling with a speed of 60.mmm3ip6 wvo4x tom 24km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreas* k; dfm*,zsyuig)e9 jes? If so, give an example. If not,*)sg, ye if;u djz*m9k explain.

A baseball player hijk: e7drg17or ts a foul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be travelingjg:r7rd7 e1 ok when the catcher catches it?

As a freely falling object speeds up, what is happj qy dll:nz -;l01qf:y,pv+jmening to its acceleration due to gravi :z ld;,l1qv+ n:0yply- fjjmqty — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ballr m6trs194 2mb(vdeyr vertically upward? How would you estima(2yb4m mrre t1rds69vte the maximum speed you could give it?

You travel from point A to point B in a car4u 6/zyx4wfkkyqk,:gw:8 x kl moving at a constant speed of Then you travel the same distance from point B to another point C, mx6 k8: q/ y,lkkg4wxfu:4wzkyoving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with fcx/jm d8jte607*rwyten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase o6 rjjy/t *fe8mcxwd70r 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 constdzm-w/ o frn8:pf;: zhahr34 - -tpzqaant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along thwa-f8 -ztp3qp;-r4ho/zhd r :zf amn:e way, a dish resting on a table?

An object that is thrown vertically upward will return to its orig3z;;q hhmu h-iinal position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motioh;hqh;i mz 3u-n.]

Can an object have zero velocity and nonzero acce;qzqoc2v1n:6u. w (zxj,b wv hleration at the same time? Give examplovnq hbqx:z;( w21zujwv,6. ces.

Can an object have zero acceleration and nonzero velocity at the same time? Givea5vpjy + 8,tjs exampl jyja+ ,stvp85es.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hintzsn.g4n :3pax : First try to duplicate the motion plotted by walking or moving your hax4.pg s:zann3nd.]

Describe in words the motia xo vgyumc3 *j2v-30zon of the object graphed in Fig. 2–29.

  What must be your car’s avxdi3hzgs+lk m9 (9m(r erage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take slhb ;+u(2r6hzl/ zxnto fly 15 km?    h

  If you are driving along a straight rfbe(g4n,da 6 goad and you look to the side for 2.0 s, how far do you travel during this 4d ,f(ggeb 6nainattentive period?    m

  Convert 35 mi/h to cam wpa+ fw)i* dm+ 31bjq rk+7vz)zg.
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fduw )(fpwm 4pyn)p 1l5rom $x_1$ = 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 steadil ui9e6bha42k: dexdz7v:kv 3p;s0 lsl y at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hoursldel2xz bsv 96;0i duvsp7he:kk 3:a4 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 txz( :f1z cw8k ufghg.8;1ow(i8mcov the following thunder gives the distance to the flash fc1 8hfo. xiowgw;m 1gk 8ctz8uz:(v(in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight completh mpl2)m gcsqeov- s*+2 ur;+me laps around a quarter-mile track in a total time of ;msepomc2 )hu-s2 q*vl+rm +g 12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in tcnt0 5md)o lg,xt0j(a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halo x0dtcnt0t,l) (j m5gfway 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 each other oq35qb* ;9tn8k,ypyvpu/ ; l rizj)/dnxi cs g(n 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 will it bedy(5q8j 3ix nvun/ gzbc,s;pqrp/*9 i) tl;yk before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a trv3vuj4vc / s+luck traveling How long will it take the c/3vjv4l c +svuar to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and 0u6qg2myl 3ncthen encounters a tailwindg2ulm0ync3 q6 that 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 averagek0xg)37r2qgu8yclm wa5tot u2 p va, / speed and average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the rettatorc 3uy2g 7 / )u qxl2pk5a0g,wmv8urn 250 km is covered at 55 km/h.    km/h

  A bowling ball travelingfkoh s+gn1i;* with constant speed hits the pins 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 ths*h+g 1knif; oe ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its avli,gydct y8f45 .f25qylr)rg erage acceleration in y.ygr 54l dfyg2q8iflt)5,rc$m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to o(w4v(ijo es:*1vqvnht9 7f)svsv+ n 10.0 m/s in 1.35 s. What is her accelerationjf*v) (vovv( n hs+evw4q7 s1oi9n:ts
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automo-sfv u m(t:ol,bile is capable of an acceleration of aboutfov -(lts:m u, $1.6 m/s^2$ 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 consi*uoq3/ j, ien8inpubj g d9xzy (1m./tant speed travels 110 m in 5.0 s. If it then brakes and comes 8nnzg(/ i j,x9y*iu1 b3j/qpdu.emioto a stop 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 starts from rest at t = 0 and moves in a sr u 6lt*ml9 0fpugfrw7:t ;soy .xnu0/traight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as uorfw *:nlx r/t69tsf y0mg70u.lp u;a function of time. Display each in a Table and on a graph.

  A car accelerates froz y/t)(x:caxa uj ;vx5m 13 m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constyxj)vxu /tz:c (;a5xaant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was i yxjykwzy8ek 0s+ p6)/dl-)qi ts acceleration, assumqx)dwjy iy yzkk80s 6-ple/ )+ed constant?    $m/s^2$

  A light plane must reach a styy w083q5n czpeed of 33 m/s for takeoff. How long a runway is needed if the (constant) acceleration iz3y tq w8yc0n5s $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of 9ouj-80j3z mzkj j,fp(th g3 ow) kcz6the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the t, (z m)zu-gpcjh 309f k8z3oj6 jwjkorace. 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 in 6emi eq *- f5c 1v/dokkfkd-64a.00 s. How far did it travel in that tdcom1ev- 5a 6e-qdfkf/*4ik kime?    m

  In coming to a stop, a car leaves skid marks 92 m long on th;vs:;e86gd a/c+ 0 khqyqank )vcfo y)e highway. Assuming a deceleration ofahvvd/) gk)yoycans k; 0fcq86: ;+eq $7.00 m/s^2$ 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 compresses and;8faoiy0oni 64ts-no:t-utek8+ ex t the driver comes to rest afte ttn :o8yiea8o- s;4txuiet60fko+n-r traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an 0sqm.jww c/6k,yri6binitial speed of 95 km/h and human reactq6jwb/cm i.0s6wkry ,ion 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 distancechf 74hz c6v p/3f:yvk 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 trvzh0dwo56qa;xgvs 7 5,h3ozhe highway. The car’s driver looks for an opportunity to pass;do55a h,wh0 rsgv7qo3vzz6x, 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-mlyiuwczrkd-9 vk10 nkr6*3 o1 run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m torn v 1c6 9rkkk0wd*3zuyoil 1- 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 intersection just as the h+tccci+ )9bv 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 stopvb+ct )+ 9chic, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped fs(+ p - oc3(rijxaw1lq,mx7kqrom the top of a cliff. It hits the ground below after 3.25 s. How high is thexx7akl+qispqjmc ((,r 1-3 wo cliff?    m

  If a car rolls gentlyi,6n-gtos zt/z ysd /- ($v_0\,=\,0$) 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 strai 1mquq7i2n c5.ngc- lmn wwl76ght up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vert.sqxo* n d nl)ia:r.v ;(vs9zfically upward. With what speed did he throw it, and what heirvnl oaf;* s: (d)znix9v. sq.ght did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls ur ysv*,4x f-j3f1jmn1g7s abknder the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to tga1j17,vfx4 sj- kymr*3nbsf = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speedj z((lgjr8; 2mzgile( of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicop;z ze 8(lr gmi(j2lj(gter’s.] t =__ s

For an object falling freelt*01n9 zr*e w mohv(pby from rest, show that the distance traveled during each successive second increases in the ratib(1 p v0r*to wznm9*heo 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,4kjqd9z,l*k n show (algebraically) that a ball thrown vertically upwardjqlnk,*k z4d9 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 vertica.v6 6 zxwjffwk -a.q8rlly upward with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple in Fig. 2: :fthw;x 3tan–18 (or number of photoflashes per second). Assume t3:xtwf n a;h: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 travel past a window 7fn;fm8 w4qi i2.2 m tall (Fig. 2–32). From what height above the top ofw4mi;f7n f8qi the window did the stone fall?    m

  A rock is dropped from a se 3tx b4. z0rakb/5wn:x h+ ;pe5dabiska cliff, and the sound of it striking the ocean is hear; 5s :p+akx/x.wez4d5bbaibk tr 3 hn0d 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose n ;o.y fng*hf7:re nc3uozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves ehnur7.cf ;go:n f y3*the nozzle?    m/s

  A stone is thrown vertically upward with rv aq(tv0ikal17e:t8 a speed of 12.0 m/s from the edge of a cliff 70(1vqi:ra t0 e8 a7ktlv.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upwarx 35xdlvin5j bku wj5(1uq9: jd by a window 28 m above the street with a vertical speed of 13 m/s If the ball nd wj 51u 5bkl:3xvxju9qj5i( 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 velocityp) lhwo2(( mvt of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleralphom2wv() t (tion constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of *pu )hj*.favz time is plotted in Fig. 2–28. What is its insta*u jv) za*f.phntaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate a- uji*wf.j4qyi jcw;uup7;dq *p0f.epproximately as shown in the velocity–time graph of Fig. 2–35. (The short flat s* ;7 iuefjw 0j*4dquf;p-c. yq.p ijwupots 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 acceleratcuwj -(:hm sp.ion of the car in the previous Problem (Fig. 2–35) whwh.mcspu j- (:en 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 distaa * 9pwwoum;6ance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose ddvq8a5tq, q g/isplacement as a function of time is given by Fig. 2–28dv,8 aqtq/g5q.

Figure 2–36 is a position versus time graph for the8bz ).gmyj1 n8mjocd0 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 posi .zm0nj d1o bcjm8g8y)tive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefig7jn su6fsa2za,hb+x4bt8m y /hter’s safety net. Thmxz/+bjbu ,4n27 h8 sayt fas6e survivor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon ve(9d-ksj 3-g goakm-0,v iyyis about one-sixth what it is on Earth. If an object is thrown vertically upwa -y ,eksv(g-0y3g d9vomkaj-i rd 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 constraivqw mdmic0k (:q,r 4.aned by an over-the-shoulder seat belt has a good chance of surviving wc 0d ik,:(mr mqqv4a.a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridgepsx) uasusx980v qzz-i*m b- 5, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truq0 )sp9-x*-8u szvz xubsi5amck 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 for front-eng/ji 1pqv-oq2yfnt86 d collisions by hauling them up on a crane and dropping them from fpnvo iq6qt-28 /yg 1ja 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 trav ;n/ z*z,gohegr 6vp1nels 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 fronmmds4z,,h8i mi9e 8bnt of the train has a speed of 25 m/s when it passes a railway wo inzhmside48, 9bm,m8 rker who 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 i (n3hiaa,ochyz-6 g 4)yife*surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the water.hf()iioyha*e4, a6 n c3g-yiz $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, igsdrm7dv53 )5g z ynpq3me y;.t is necessary to balance the average speed of a train against thpgm5znms);deg37dyqv r5 . y 3e distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two 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 st3* njl(vdbjdup t+:9 uraight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once c: pjlu+9* dbt3duvjn( ommitted. 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 a ball is planned so that td vvovvotl4 n579p,;mu 0jkqg sr7.9 zhe 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 q koguvvdr.9s05olpm z7 4n7,tv;9vj. 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 81 yr/x21)cwj*heah/ erve vua freight train traveling at a constant speed of 6.0 m/s Just as an empty box cywev v1 ruhx r*e)e2/j18 /cahar passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high b dnk8 j4/v ; uahs(ekl5xszl3:dv i;m,uilding. A second stone is dropped 1.50 s later. How far apart are the stones when the second one l5dv4ln z hx v;mu k8/adesi( 3;,j:kshas 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 :km,dy usyu7 )lasting ten l m)7,u yyd:kusaps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mouw whi gw*:2yzde. 3mp/ntain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . Wm. w* hpez:w3y gd/2wihat was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. Th1 arq*edp28 rae first child can bounce up one-and-a-half times higher than the secoe2*ra8 rpa1qdnd 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 1.10wpsp+zc3 d 4k6f(s t/r-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are travel/tpcps4z + 6( 3fwsrdking 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 b4yae(lerjt u+qei :6wo k t069aseball with a speed of 44 m/s In throwing the baseball, the pitc 6ijk t(e e+e4l:yaqw6r09otuher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, w/0 hli 3.(nrqtqlsi;aith 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 intersection has a traff /hkj91 (iu)wxf(cj.t(t y fstic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from ff s )wxt1hu .jtctkij/y(9((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, passedgw(nzd2*s-swzb:d d * by a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a c s2ddg*wwzs(d :-z*bn onstant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a second sto5m vpu vr t o3l,3x;(dh/fvrjr5 v;j5kne is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same time. (5 3r ljt3 d;ovrvfvx hjkupm r5,v;/5
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone i4olcgyh8w p6 /d/ f lh1 318k5uelmgxxs 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 velocitp g4l he/ klx8wlcudxf3165h1 o8y mg/y 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 w2:nacp p75 ;kmz drlo-ould 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 zc adpol7rm;2-pnk:5 ? 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 belt to send the dtiue* 0;,,* lej ee/o5d gocfburgers 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 sutcf*5d ejeo,l *;g/,0ioeedpaced 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 timesfv1mkx m 8i38ylxhz 7b zwq,dv7u t7w50w 3ro( faster than Joe can. How many times higher will ky 73wf zd 80(m57v 8xz h1rov7xut qwimwb3,lBill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground belws3ds l54fv d/ow you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws sw5df /d34sl vit 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 a bar)skledgu)+gs19m+ w; m)vaffometer. 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 0.3 s make d;fgalmeswmk +v)us 9)+)g f1 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) Is 04 : caq.czlhcthere 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. cc:0qcha zl4 bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?