Does a car speedometer measure speed, v m,zcq y8s - 3zsblcecmo9j71/elocity, or both?

Can an object have a varying speed if z 7b53ae h:rgbits velocity is constant? If yes, give exam 3hgebbr:a5 z7ples.

When an object moves wi2r m*txf12jcjq r*zl 3th constant velocity, does its average velocity during any time interval differ from its instantaneous velocity ajzt2jr1**f l mx rcq23t any instant?

In drag racing, is it po,em0bqo4j)3ramhd/f b 4(m tgssible for the car with the greatest speed crossing the finish lb/b)04m hej (dat mf g4mor3q,ine to lose the race? Explain.

If one object has a greate8xvh ae;bzd+r49hxa; r speed than a second object, does the first necessarily have a greater acceleration? E e xb;raxd4z+;8vah h9xplain, using examples.

Compare the acceleration of a motorcycle that ap9x 8 avhv r:tc/k ijlk-*0kq8ccelerates from 80km/h to 90km/h with the acceleration of k 8ah0*-vrj8pkk/ci 9xvq: lta bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northwdc p u 1i4r/oj)(gqkn6ard velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is p jv+ y /c umjw*o: ;2n8zh)5zvavlai.lositive? What about vice versa?vn v u lvw5+ljz/*8ja z;.ia2)cho:my

Give an example where both the velocj8qj;ndiz+j7hd ;i9q ity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car p9d ( i)l ix*d -hnoa6owv76auA 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 .po6 i a97-nw v 6hil*dx)o(dau Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasie ( j47emp,3v fes;rmn4yc 5xfng in speed as its acceleration decreases? If so, give an example. 4cerffe;se,m3pm75nj vy( x4If not, explain.

A baseball player hits a foul ball straight ozoikn 6y )44pup into the air. It leaves the bat with a speez4pkn4o)oy 6i d 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 speed/36 upnxjcep. s up, what is happening to its acceleration due to gravity — does it increase, decrease, or stay the same?6 j/up.xencp3

How would you estimagm m.5:e8x;ui0m8jp c c5wk adte the maximum height you could throw a ball vertically upward? How would you estimate the maximum speed you couwkjd5a;pu.mi8ec m0 m:8gxc 5ld give it?

You travel from point A to point B in n, )(lsuzv3m.,/ aghz e)jn(xulv 0lta car moving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 9v(a)g,l ,jh0 l/xvetl3 zuunznm ).s (0km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstratio5 nrcdsc)5m-+rj pnw ;n, a 3.0-m-long vertical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string rrpn ;m5-5ccjsnwd+ ) 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 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 consbgi4bst)2+ xfh; ny)r tant acceleration: a rock falling from a)txbr 4bhn;+ i)s2g fy cliff, an elevator moving 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 upwartwel32 m-sb5 td will return to its original 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 acceleratit es tm3-l5bw2on due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzerog,j8r: krcw mrcg 5:b5 acceleration at the same time? Give ergwbjc m:kr5: c58gr,xamples.

Can an object have zero acceleration and nonzero c/siv 4(5 :f bys/usu-wb 6bluvelocity at the same time? Give examples.:5b /uvu/lcs-b4(bfsy wiu6 s

Describe in words the motion plotted in Fig. 2–28 in terms of v, a,* 21 *o.io*jwlrgfo ep etc. [Hint: First try to duplicate the motion plotted by walking or moviri p o1lwe*o*gj2 .o*fng your hand.]

Describe in words the motion of the object graphed in Fi jo30g0f8v dtog. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.k1in1xq:bu v.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 1h 4e tzhnt1cigul299; 5 km?    h

  If you are driving along a straight road and yl:vtg5r7 n9 akou look to the side for 2.0 s, how far do you travel during this i7av5 l rn9:kgtnattentive period?    m

  Convert 35 mi/h to ohvbj6n3jmrl9 2- c;u
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from sqgr,-3 mb e590cuvk ptm-l 5v$x_1$ = 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 beg f;t wzd*w g0fyjx16)cins to rain and you slow to 65 km/h You arrive home afterjf)wtg; x1 dz6y* 0wcf 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 flas8-el2df zitx 7y 0xom)h and the following thunder gives the d2z i78 x-ydfletm 0)oxistance to the flash 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 complete laps arouov(9+ np.gy p:.ltz f1xp shj6+ouhu/nd a quarter-mile track in a total time of 12.5 min. Cgu6hupopyt+ ./hjo n(+p.1s9vf: zxlalculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straig sqnhg:s5og6oq si:dgp18 ))xht line, moving 116 m away in 14.0 s. It then turns abruptly and gallops hgqq):6p5i8d o)hs:o sng sg1 xalfway 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 on parallel tracks. Each has a speed of 95 kydssx+v)ns7)u, h z/km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).hsxz/ s+v) kn)7 uy,sd    min

  A car traveling 88 km/h is 110 m behind a truck try)6 am*wyf g*paveling How long will it take the car to reach the tr*mw*yf)ap yg 6uck?    s

  An airplane travels 3100 km at a speed of 48 a5d(zvgn oi790 km/h , and then encounters a tailwind that boosts i8i d(4ang vo5zts 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 averagex5nh2aj(kk0 umsu)b 8 speed and average velocity of a complete round-trip in which the outgoing 250 km is coveredu kx80u(h)n5abk smj 2 at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hit ge /qu.lj*k/a /laf+js the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the bkjuq ef //l+g/laa *j.all hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95sx2 b6 krydj( 4usfo4vk4i)7k km/h in 6.2 s. What is its average accele )4rsy44k27 bvfdkos6 j(ixkuration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. Whatb q,y ;f+ :c1jxrxab5d8qp 7rp is her acceleration r:cjfxbd+17q qxy,rp 8ab5; p
(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 acce4 7kzvowo t+,cnv0u7 ileration of abouvzv 4nu ok 77ti,+0ocwt $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s. If it tjm-hc o0jkvir)-c w:*hen brakes and comes to a stop in 4.0 s, what is its acceleration in:j- c)vwmi*o h kj-r0c $m/s^2$ ? 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 atxsx0fw6ov :+ v 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 exfw6ovx 0s: v+ach in a Table and on a graph.

  A car accelerates from 13 m/s to 2 l4 prk1fn/ 0:v-qr1 arjzak,p5 m/s in 6.0 s. What was its acceleration? How far did it travel inv4qk1 zl:pk,p 0/jr-raf ar1n this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a :j;kp pd7m:tgz /vr/(2gb dgsdistance of 85 m. What was its acceleration, dv2r gt/ s:7pmk;:gdb(pgz/ jassumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runzp7w*vsjq); fway is needed if the (constjs zpq*)vw;f7 ant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter c;r 5ajunmv :,r t5 lvfq9,pa.eg* 7ssban burst out of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the racva *5v :unr.m, ef59jpssgtbla;7 q,re. 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 6.00 s. z6hqab7t0 z0mHow far did it travel in that 00 h7ztqb6 zmatime?    m

  In coming to a stop, a car leaves skid marks 92 m loni.rej b4p /,ayg on the highway. Assuming a d y /brejp.4ia,eceleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 k bc.o63eesd,b+m8 t bgm/h strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What eb3,8 gs tcb+ob6e m.dwas 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 initial speed of ::b/c9rq/pbv0/ wt trsyj j2uio-x fl4z+ lt595 km/h and human reaction time of 1.0 s, for an acceler o9qzl b j/t spv/rutc r lw04yj5:+:tf/xib2-ation
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distancec/ad 81 jx/xdp of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s drivers 6w5yq,eqbb( looks for an opportunity to pass, guessing that his car (se,bb qq65wy can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 min. After exaci-ttpq/nl u8if (6fp 2tly 27.0 min, there are still 1100 m to go. The runner must then accelerate at6/fit ip8-t l2(qpf nu 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 the8,v g w89+ zqsud/w5z,maubmb 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 twm8d 5+zgbs vubza89 m qwu/,,urns 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 tdpc71m h 88j lqjv(vjib9/k w1op of a cliff. It hits the ground below after 3.25 s.mj18 79q vkibjl/jcpdh18( wv How high is the cliff?    m

  If a car rolls gently eqilgck l8 (icjxz4r4 0 pv :8kh:mk8g*8ms*v($v_0\,=\,0$) 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 withav 4,h sbz-+xo:iinq: 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 verti-uudz y+) nzusbq75bep1+ju (cally upward. With what speed did he throw it, and what h(ubnz)1 pquy-zu+ 7ed+bs ju5 eight did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Dru y(ny 5uwqw9x bgaa*k/v n*0w: mlw41aw graphs of (a) its speed and (b) the distance it has fallen, as avyq(u*9g45 0ww a/luww:a n1yn*mbkx function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a f czje8qas g/jes x9*e4 cip5i+cq y). pv85z-speed 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 heli*8ix+c j sce v qppzsq/cg4-5z)j5ey8 a. 9eficopter’s.] t =__ s

For an object falling freely from rest, show that veq3 h(3b wmf/the distance traveled during each successive second increwe(fb /mqh v33ases 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 (algebraically) thatpla/*xfvi:j 2ao 2v+b:u xk/l a ball thrown vertically upward with a speed fx o/x l k+bi2vva:*2ula:j p/$v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vep4v2 a ehn) *rfypv;x4rtically 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 photoeqi (7udq g 0.zawd9y/flash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple pi 7/.ddwgq0q9a uyz( eositions, 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 2.2 m tall (zb vrs6ty69 -pFig. 2–32). From wh 9ryp-6bzvt s6at height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound1 a18 fpl.pkee of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how1ee.8k1 fal pp high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard strea rg;yjsmj q4:q 6 :kqa).qw4jpm of water. You point therjjkq.44qja sy :)qp:gw ;m6q 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 the nozzle?    m/s

  A stone is thrown vee,zd+s6hgj ;2 *lwddx rtically upward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34l*, +xwz;h26e dg sdjd).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the street with a klgvbk:a 1w0bl4j* q zk):iz.vertical speed jb4z v1lq:)k0 akk:z *wb.ilgof 13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a trailmjw 1j++e)q d3h,ut lj7kpc3n 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 acceleration constant? (d) Wh lm,+luq + 3d7wk3jc )je1jphten was the magnitude of the acceleration greatest?

  The position of a rablzd)gq*m3gdcqa )u bt1x( 1s8bit along a straight tunnel as a function of time is plotted in Fig. 2–28dz gduq11)*bgla)8x (3c qmst. What is its instantaneous 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 approximately as shown in the velol/u )wkv 3; z)bzjic h9fu1 z.to+(,m wrlw:eecity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of thefl +w:mrtjv) z/b 1hez 9e wik ;uzu3,c(wo.l) 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 nauo51k5xirfu wa(*v5j )2 sqthe car in the previous Problem (Fig. 2–35) wri(2w5 *jf n5a1qu)sx5kaouvhen it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance t r:w sa0ud -fl1t;xt;jhe object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whxj6n2d6rh3l*j, d k nsl+wv- sose displacement as a function of time is given by Fig. 2–28.lr,62w l j*sn +ksdjx6hn-3dv

Figure 2–36 is a position versus time graph for the motion of a-wje nvpi on4pe. -3jr8z17lcn 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 accelera3vp8o 1.7nj-4j nlpw-re zei ction of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story 4cdlv(1(r3gp (*uv jx oo s*dzwindow 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m bexpgd4jro1 lz **(3( scd(v uovfore 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 abojvj5dh .u13h 9 jnjwo-ut one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many od3-jwn95 1ujvjhjh. times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by trtm3t.q-va,v9w* z gh/lu e1 an over-the-shoulder seat belt has a good chance of surviving a car collision if 1 ttghqv-w9/.* zvr3utae , lmthe deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road below, and his pjsgicf5g/5y6 n- v dm8ursuers 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 t5fg6dcs-m vj/g5iny8 he 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 frop5/g6lc4g p,ur ekbs:nt-end collisions by hauling them up on a crane abk:p c rle64,g5g su/pnd dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth q*f: glpkm1(1uz,zwi travels 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. T3jym0 iawo 8e.he front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the work ywaj0 8moe.3ier? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’iod9:w.u pqwq1 v k8n3s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of th8oqpn3 wvu.q1w:i9 k de water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balance the averagg1o+ i0vag7fx smu+xnnb: k- 5, wuzo,e 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 1voxkog f 0nax+7:i-gu,n+sb wm5,uz 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 wingg8 fl(o /kchb2s and 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 committedol /c (8bkhfg2. 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 ar5fekv.hs ;/xj4vls:x 21hnstrikes a ball is planned so that the ball will stop withi/ aes4vn:r1. hx2f5v s ;hjkxln 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 difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at a constant slz6a16ua :jna0fq a.speed of 6.0 m/s Just as an emuja:a0zlas6f6q a1n.pty 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 the rooox+0 )m959t qcjtkois,gze u-f of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a speed of u-9gje0z socmt ,+kt o9iq5) x12.0 m/s ?    m

  A race car driver must average 20j0f,byo ,n7 ro/wta:k0.0 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 maintained for7/,: y jr0otabfn k,ow the last lap?    km/h

  A bicyclist in the Tour dmr+j 2 zuv8-eze France crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/e -mz8+2jzru vh . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bounce 1b php/m-0lv7( o,qgl/fn *w gp(hidj up one-and-a-half times higher p -m(d1*/h / pbvli0qg,njfwplh(g 7othan 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+mka4avp wd8; kxf04f km/h overtakes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have travele8wv4mp; ka+kx fad04 fd 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/s In throwing the basjcy2*eye (*s ig0a lr0eball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the bodyyc(j glais00 er**e2y 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 g a;j 6agxu,uyv8uvb(t0 ;(0g- dw o +sdvxyk-rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Ea8g,-v7jf1xd npy9 tygch intersection has a traffic signal, and , gt7 891vgydf j-pxnythe 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 consta 8 krxsxu7;8wyt 9j-hhnt 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a hty; -r7s9x uwk88xjh 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 f6+;zc).r (jhxrnj oc be5c0uv rom the roof of a building; 2.00 s after that, a second stone is thrown straight dowc uo6e0 cnzj5;(hc .v)jbxrr+n with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertica-hpvt7yk*b6d ol41ojlly up at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor baldo j*1kt4l 76 poy-vhbcony 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 itp9 0 dj4qg /rek 1pefbh-pao)6swir7. take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcor7e-.)p rf6qgoj/kw9pb d 1ris0 p4ehad? 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 , 0dtos: st8x0+s1c(4xiu p,tmh ocy ym 34nensend 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 spcs0o3xe(cspuo148 n ,iy m ys: hm,+4nt0txtdaced 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 thanw6pcc4 r5iq.7vfr /o u Joe can. How many times higher willvuprqi/wc 5r6f7c 4.o Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a v rh:ib+iv2u9((hfd acliff while your friend stands on the ground 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 and throws it up to you, such that it just comes to rest in your hv2uhabif+ h(9 riv (d:and. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular buildinkp1h.-vxr* cvec-ku. t i4r w8pi* e/bg 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, *.e8 e* vw1-/xkpkpc 4rhc uirb.vi-tand 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 kb3;i7v dgfn9x ,t0ud graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the7g,9vi kd fdu;03bn tx other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?