Does a car speedometer measure speed, velocity, o47m 6vq tnrk,+9*dko + 9fhkjsk dt.qzr both?

Can an object have a varying speed if its velocity is constant?m6aoh,oxkag5- 49ow dz9s ae) If yes, give exampl9 mad65 )xozw9g4akeo ha, so-es.

When an object moves with constant velocity, d6a+kjga k 1k0terwi 7gw)9iq.oes its average velocity during any time interval differ from its instantaneous velocity at any i0wjkta7+rqgii19a6 wek.g) k nstant?

In drag racing, is itc;v 8,li;r cyfr81wxhry(qj8 possible for the car with the greatest speed crossing the finish line to lose the race? Explj l(8 y;ch;rixvcfqr8 wr,y 18ain.

If one object has a greater speed than a secon1,6nhc i9f l-,sa-z9d jqpzvqd object, does the first necessarily have a greater acceleration? Explain, dp1nq,- ,jzfql9 h -icaz6s9vusing examples.

Compare the acceleration of a motorcycle that acceler ce 8ihzjm9jq8/;jc5( wy (r8s1owyctates from 80km/h to 90km/h with the acceleration irw cey9(( y8w ;j8sozq/tmcjh5jc18of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward accelj/d v0 r(1zl3 a/jvd1u c3pqpzeration? Explain.

Can the velocity of an object be negative when its acceleratio irvox7rh-co9k j0 3;mn is positive? What about m;9oc0hkvo3rr7 - jix vice versa?

Give an example where both the velocity and dfw+;liu .pj -uw jjpo1,4/hb acceleration are negative.

Two cars emerge side by side fromrr (x-ty1mzi j2(4std*lfc*8gtw.em a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tf.tlr8*cdy4*- tsgix jmewm( z2t ( r1unnel? Explain your reasoning.

Can an object be increasing in s+z hn*a7bt 0kb74rkqqpeed as its acceleration decreases? If so, give an exampleq+bhq akt4zrbn7k7 * 0. If not, explain.

A baseball player hits a foul ball straight up into the air. It leaves the bat( 1je8prb 3u iq5ngxb6*e6ecf with a s(g b3neu61p8 5 bjrcfix6eqe*peed 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 happening to its acceleratio t-xx9/j-s rdxhbmcuwzs/,-o58 xe 5 wn due to gravity — dwbd /c,o-uxx zs85/trm--j w95sx hexoes it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a bhvp6yb8 3x +c zl4h6xsall vertically upward? How would you estimate the maximum speed you could give it? x4hv866hl 3y+ xcspbz

You travel from point A to point B in a car moving at a constant spee5i47llxo(h tz a*0eta d of Then you travel the same distance from point B to anoth4eat*5hxoz( 0 alt li7er point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstrat -kh2oa2 j8ixmu( vb6xion, 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 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 equvo68jh( bx ai 2-ku2xmal intervals?

Which one of these motions 6bi .:9-lfwtl 4dexy3xcof+ bis not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a tab l4- d6.l:9+ ctobxxf eiywf3ble?

An object that is thrown vertically upward will return to its original positbigh gnk- 4;9zz.7tyuion 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 z-h;iuykg. nb79ztg 4so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero bf jer:hpun-0f ;ks0b ) h4ss1velocity and nonzero acceleration at the same time? Give examp0;p:0eu4 n)bkfhjrs fb1s sh-les.

Can an object have zero accelerati2 bbtua4*/ ryb6w,0zkr1g ec won and nonzero velocity at the same time? Give exampleeb4b1 bct6kwwu0r yazr,g*/ 2s.

Describe in words the motion plotted in(0f y/mlb a :i j;8f)aeevm,otel5:ma Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by ( b/vlj 05f;aaemo fy: teei8lmm):a ,walking or moving your hand.]

Describe in words the mo4vqv9h. ,0sxcs :ka p al8 -oqfsnx0j)tion of the object graphed in Fig. 2–29.

  What must be your car’s avq*s(c17p(y d kp, tkhlerage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long gbo8s/*vhx wb48 6c zqdoes it take to fly 15 km?    h

  If you are driving along a straight road and you look to lss:vnmj c 4+2the side for 2.0 s, how far do you travel during this nm:lc24s+j sv inattentive period?    m

  Convert 35 mi/h to 9n648s q ufy/ki/h ul+dl8dvb
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves l ga4ux:u7zv.from $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home from school steadily at 95 km/h for 130 km. It+ a y ,.ufr7d,oueyvd, then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20fr+ a u.e,ydu7vo,yd , 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 s15 fufpb byg -08+tqbfive seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arri tpyq5fu 8g0bsf +bb-1ves 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 around a quarter-ou.g;ecj. c jhd68tn;mile track in a total time of 12.5 min. g.ud6jc;eo.c8 jtnh ; Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its pazc+6/yjo +8q/mf2tyjv*a g trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4. myt8oayg jj6f2zc*+a+v / /pq8 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 wz kg + 31elwm1w43h5om6rc zo95 km/h with respect to the gre3mck z1whm or+w1z56w4 lg3oound. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How long wiiy(sy+vv1sf ,r s* ty1ll it take the car tov1y,1vyrstsf( +* iy s reach the truck?    s

  An airplane travels 3100 km at a speed of 79*vktzl2)93uneqsqeqe(( wo2,qjsh (d ny;7h0 km/h , and then encounters a tailwind3sn qh*wqlek(9(e2q hn )outezq(v2 sj7;d ,y 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 average speed and average velocity of a complete round-trip in9hdva ,w-yofg 66kj z0 which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour -a,9dfo66hg j k0 wvzylunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hit)2n z kulu5e d+duiax9/ +b:res 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 the ball is rez:udb 5r /2kduue )9in+xal+eleased 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 ka1lzhc,(hxld76j .x/h in 6.2 s. What is its average accelerati.a7l x d6lx( 1,kchjzhon in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from resx1)p:x9j q/smuzsh 98 mou1pem)9h hnt to 10.0 m/s in 1.35 s. What is her acceleration nm:oxs )999usu)xmhq j/e1h1z pm8hp
(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 accel)4o8xcu7ewud48 psz qeration of about q wuoc4z4s7x88uepd )$1.6 m/s^2$ 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 th6kaj73f s ds4 c-j- wn,tz-45flwofccen brakes and comes to a stop in 4.0 s, what is its7--fof-nzl36 wa54djsjwksf c 4cc,t 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 = 0gd.z/ly)r n012df vsk and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph. kd v2 ds1r0.ygz f/)ln

  A car accelerates from 13 m/s 139*nh8d5b eus uxhwbto 25 m/s in 6.0 s. What was its acceleration? How far did it travel in5* hsb nhu 8dwx39u1eb this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a-2bp-2r b ,x p3pu3;x nospgs/zpxq, k distance of 85 m. What was its accelerakz/p,; r spxo n2-,bp-bugp2xxq3s3 ption, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. Howmx f dxx hl2 p+p7ycn361g1u7t long a runway is needed if the (constant) acceleration is 7pmp ltc 3gx7u+xn1f2h6 1y dx$3.0 m/s^2$ ?    m

  A world-class sprinter can burst out ofv2d3+r4 7 yce3fy+1oj31kedkch yf md the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the averageom2+d 1cy 3j +d37ev fdfry1kye hck34 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 resbqr 7+k,7ok3i epbh:hzh , i5rt in 6.00 s. How far did it :7 ,kpiboh+ ikqh, z3r5ehr7btravel in that time?    m

  In coming to a stop, a car leaves skidcfj 83;9 dyizpf*u nr: marks 92 m long on the highway. Assuming a decele9p ; :38nfy*cirdujf zration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compress(11 wtvpxfh6viq4s6 kfx(-t pes and the driver comes vv1( ift txs61 phx-6 4qpfk(wto rest after 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 anc hjvcpkr(1(4 v2s f+h initial speed of 95 km/h and human reaction time of 1.0 s, for an accelerati+r pjvv4 (chch2 k(f1son
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equatia *qjrgcxmis+;)dw av;)h;ue 6 wjn:* on 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 the highway. The car’s driveh pqr/*zb 7;wzyo*lr(r looks for an opportunity to pay/pzol hb (7rw*; z*qrss, 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 than 30.0 min. After exac-x;nzhab- gve iz2 4(stly 27.0 min, there are still 1100 m to gh(z-agxne zb 24 -iv;so. 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 intersechn0kf8r w-,(kszr/m ation 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 sh/8,kwkh mar0-sn( rf zould 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 from the top of a cliff. It hits the ground below after 3.25 ngb7vue o4)(p s. How high is b)vg np 47ue(othe cliff?    m

  If a car rolls gentl7 3hllc8nzj +6 xx 0uelqx58dgy ($v_0\,=\,0$) 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 nea+*k:c1 3hposwi +fynv rly straight 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 afte5lj8 ig 4gocp:r throwing it vertically upward. With what speed did he throw it, and what height did it reachip:ggjl5oc 4 8?    m/s (Round to the nearest integer)    m

An object starts from rest and falls u9 /6h8tjhqzfd nder the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time fr hj 6tdf/z9q8hom t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with r, g-ya-5bu vn3mbeg4ti1fxs3 d v;(p a 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 formtrs ia34b;yuxvdfn(b g,g-5- v ep13 the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the di 2rb s 3 tj- y.d4yn*p0noefeu5hyd3k/stance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown yj eytbd se/-khfp0o42ryn 53*n3 .du by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neo-) fe1ko a97 vo2wi2ae.dc ju2v)jmcglected, show (algebraically) that a ball thrown vertically upward with a 9 kfwc 1o cja7moov2)-eid)v2. 2ujaespeed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a sp6x4 -s 6eu.i-pwd vcgveed 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 (ox: guj s3tvq/voh7j3 7r number of photoflashes per sectjshvgvx3/ u 7o73:qjond). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to trxq q kver1*mk/m,*ae 2+6iuufavel past a window 2.2 m tall (Fig. 2–32). Fro mq1u+u , v*6kmrx*ieeqkf2a/m what height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it strikingp2y za g f(idko0v*o25 the ocean is heard 3.2 s later. If the speed of sound is ka22dg0f5*ipoo v z(y340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a harhw2gfqxr 7m* d7cc2* gd 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 the nozzlchd *7g rfg7* mcx2w2qe?    m/s

  A stone is thrown vertically upward with aez4 x ou4 n*f;ly91ohnik*6aoq4cjx( speed of 12.0 m/s from the edge of a cliffknqa4z4n jo6xo;1e9xlc * y oi4h*u(f 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 pass upward by a window 28 m above the street with w5 jpue 6we:(3dg-cv 7mhbgt 3a vertical speed of 13 m/s If the ballhm3v5pcugwt- d7ej gwbe: (63 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 timwkb3hv3 a2.r:tie+c ih oa4 87 k6unxje. (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) When was the magnitude of the acucrko.38tx w+bh aai n2jhi k76ev:34celeration greatest?

  The position of a rabbit along ash2 du(0ekdu. straight tunnel as a function of time is plotted in Fig. 2–28. What is its (edkuduh2 0.sinstantaneous 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 appu9 .) lct0vd9eqwsta-gd 6xn1 roximately as shown in the velocity–time graph of Fi9-au t69dx1 elg)qcnsd . wtv0g. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the c rljqwy8z- vm.8*6-ewky 5b wwar in the previous Problem (Fig. 2–35) when iy-w8z*jwwv 6e. myr-8wlbk5 q t is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveled during xjb49 m; +u0t-9gzy7 zqx pz5q) oidzw
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose disp zpys zt2v /2mot2g47g jzhr0.lacement as a function of time is given by Figvtg20z zy2h .ptj rm7z4 o2/gs. 2–28.

Figure 2–36 is a position versus time graph for terb)q3 ;ip2 ex0sujw8he 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 pes;r28ewq3p xij0bu) ositive 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 -aty q1,nmyof, i5u0n 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m bef1n-yao n m ti5,uq,y0fore 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 isuwen37 ge0vh 7 about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it wu7g0w he7e vn3ould on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has a govhv:k*k fi2n: od chance of survnkvi*:vkf h:2 iving 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 bridgam;;3u ajq 31vtu 4teue, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the teleph34 qu;1uvtt;ejm3aa uone 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-end collisions d ew*, 36c5tjvo-a4lv(w(tteb (xsq gby hauling thead(w s(6 3ex54 t( we,j v-tbqotvlgc*m up on a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels abog,0h28 26x wruz8t 9aql .wqelxyfb -mut $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train bel4.o w kvp +4,mgycuv)gins uniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m yk,4) p. u4movclg+ wvfrom 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 f03jt:-iz03y ehtdy gboard 4.0 m above the water’s 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 per3yytegfhi3-d0t 0j:zson 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 thrwkevfnf4hu-o we473dt5 0z / e 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 trieh75woedr 4tuz wv-f3/n4k 0fp in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for kag 3jip8q7mcb1+has.; uap:)5j, bd3tfmt gfish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican .a7):adbj i,pg53 mj8kfumc+ pab tq1tsg;h3to 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 thxeay3q2q8f95j7 mq0pmy 3tivq ,/ny jat the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is m3/j0 pm32 qnavqqyxfe8y7tjy,5i9 q 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 ; lfrn6tw) st,train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest an 6 ;nls)rfttw,d 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 mh5*5zj p;srx roof of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has rs5h5p;*rmzj x eached 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 las8 rr; gq5iy8mwu *os)mting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintai; w5yiqmugo)m *8 rs8rned for the last lap?    km/h

  A bicyclist in the Tour de Franmasi97/k c6 /d 6koqvbce crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . qas7 kc/m/ ov6i9bdk6 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 chgtwi6 ar*b(8 4jkk8g mild can bounce up one-and-a-half times higher than the second child. The initial speed up of the secon(m kg a86t*bwji48 gkrd 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 o6hxy h7m61s-o.l x2ug vq xv,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 dovl 61 sxhq. 7xhyg2oxv- ,omu6es 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 baseb 6q;q 9hj(xljtza/z2 d-,qxghall with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a disjjazz 9d qx; (hhtg,l-2x/q6qplacement 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, witdwwl 0 cetei z:gb32:6h 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. u+75na 5m g2tywlccc 9i *f)ncEach intersection has a traffic signal, and the speed limit ismn i*5c 57alyc nu cwt)cg2f9+ 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 constant 120 km/h takev o lvc,:n8i7d ks2.pes oi ,vdp8: e 72sc.novklff in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after th4m nl;r/jn;wjg7tt apt7 ) .7)zstm qiat, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stong7n ttrt7)lj4 nwqis.z pa)mjm/7 ;t; es land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first0a:wu8w avant.0zlb0 stone is thrown with an initial velocity of 11.0 m/s from a 12th-al0utwb. zna80 0 wa:vfloor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how bouhkvw3 hs x7/(yx+) long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to pby)+hxk/ x(ws u7vh3oerhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through a 9 cxr+ocr fu,/ns+fy *grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the con +r,c9y+/rusxfo f* cnveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faste wteb4zi*cd8:(su8 p fr than Joe can. How mancs4 wib (8tp euz*d:8fy times higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on tn6xfqd *1tof+ mq.9 8fhzdp:ahe ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit th q: do9* n1fqffxaz+hp.d6 8mte ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked tq)y ( vub,wwrr;4zqxk 2ef ; z.mi4o;mo find the height of a particular building using a barometer. Instead of using the barometer as an altitude-me) ;q.rimv m4eb4uwz;x yqowrzk;(,f2asuring 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 for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph rg 7 mwakdc+t4(0p;hi 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 the other? (d) Which bicyp+ rwcd;mh t(a7g0 i4kcle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?