Does a car speedometer measu-.pcdf(vg )kh re speed, velocity, or both?

Can an object have a varying speed if its velocity is (,-v gy6uvjt.m mgop* constant? If yes, give exa6(.tjv gmvypgo, u*- mmples.

When an object moves with constant velocity, does its average velo 1eom1f+lzd vqf3. h7nx /uwhq:edu-9city during any time interval differ from its instantaneous velo9-fmqunf z1h7he1. q: +uew ovd/ l3dxcity at any instant?

In drag racing, is it possible for ap)yw9n3c:pk c(h1m r ;32hzljeqo5tthe car with the greatest speed crossing the finish line to lose the race? Expl1tccomyr 53h (;ea9npl)wkp:zq2hj 3ain.

If one object has a greater speed th dni*+q gca;9:otsi6 dan a second object, does the first necessarily have a greater acceleration? Explain, using exampl acg 9i6st+ n:;did*oqes.

Compare the acceleration of a motorcycle that accelerates fr +j 0cknp:w :x7x:imvb4f3cqjom 80km/h to 90km/h with the acceleration of a bicycle that accelbi x3q:mp 0cjk:vwcfx :+47 jnerates from rest to 10km/h in the same time.

Can an object have a norttmt-w/xh-wx m.db,eid-;6 tvj i u. i+hward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive?s0e mug+yh2. q ox6+c-ifv*st What abo60ftui2e sv - +yqgx* so.h+mcut vice versa?

Give an example where ssvt 36l k2s4brc4wjt )6*oukd6;lh gboth the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveli 6 fvsq8z.uu1mng 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 amv u1 su8q.fz6s they come out of the tunnel? Explain your reasoning.

Can an object be increasing in hrta3qy*63ze )g vxl; speed as its acceleration decreases? If so, give an example 36 xegq3lt;)*hyvr za. If not, explain.

A baseball player hits a foul bau),g:)ji*j*g r rfbwsll 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 travel r s)bjw ,gi**guf)rj:ing when the catcher catches it?

As a freely falling objea6mz,max -dqyf1 ly8. ct speeds up, what is happening to its acceleration due 6 8qlf1z-dya xy.ma, mto gravity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you c9:w:s ,ff;8bm bidlveould throw a ball vertically upward? Hobf;9 :vbmfids l,: e8ww would you estimate the maximum speed you could give it?

You travel from point A to p7p3 ppfnhjyl6;sb1 *goint B in a car moving at a constant speed of Then yoph; *b y l3p61fsgn7pju travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstratioc 9flh 9gij z)eb8r qhl(876qmn, 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 b79hmz9)c (frq h68g ll8jqieon 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 aj dgr61cd0l5s t constant acceleration: a rock falling from a cliff, an elevator moving from the second fl1cd06 j 5lrdsgoor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upwg1ewf73xxe du0-wu m2otb0i ;ard 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 acceleration due to air resista xg;7et u0fw0-i 32oem x1bwdunce is always in a direction opposite to the motion.]

Can an object have zero veloc kza0 n9edu:nz; c9jitcq372 ezuhs*3ity and nonzero acceleration at the same time? Give :*eucznq9d 2uac3i; hs 30nej7t9kzz examples.

Can an object have zero acceleration and nonzero velocity at the sg2fmlr dpm1jo w-:j1 2u)fqe-i* y47tslyf(kame time? Give exfo) y2jp: g(rki4q2lu-7t*m e1 y1d f fws-lmjamples.

Describe in words the motion plotted in Fig. 2–28 in terms of v,p* il8kru+f.zxmqdr;noc; 1.y 0 i/xf a, etc. [Hint: First try to duplicate theld*inq;/.0pxz.off8u m yxrr+ 1kc;i motion plotted by walking or moving your hand.]

Describe in words the motion of t w2*v0xo)rjvt)6zfrxosx)o; he object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.22lt8l- qakng2o1h qtg l, 4z/mv:5vsk 5 h?    km/h

  A bird can fly 25 km/h How long does ih3a/r- dr5 b df/c6eeyt take to fly 15 km?    h

  If you are driving along a straight k,c tbt+fy;b1*oyw3 blj1f0 hroad and you look to the side for 2.0 s, how far do you travel during this inattentive perio;h,by0clf+1 wj *3yttbb ko1fd?    m

  Convert 35 mi/h to iq)b:w n , tk(nl3n/nv a*z;c yoz9rp7
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves2vxt2- vtb h5a 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 tkvswv9v.ck ;3 hen begins to rain and you slow to 65 km39 kv vw.vc;ks/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightnino;ak6mnqk9 p 9g flash and the following thunder gives the distance m 9pk;n 9qaok6to 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 around a quarter-mile trajbwliu pk/g2w(;hd1r,c5 )l dck in a total time of 12.5 min. dk);r/blwch w g5 (2d lpj,iu1Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from i;s8 )i ri,x( 5dxft*(lc.pi tjkt l)mets trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly andt;lte *ixftp s d l8.,5(kr iixmc()j) gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each oth1 dx ocd.wdsq+/uf/4 jer on parallel tracks. Each has a speed of 95 km//.x /j1od4 dc+uqwsfdh 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).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How lonw+ -q8c u4k em/3kiuxng will it take the car to reach the truck?e wniqx8c/-m u43+ku k    s

  An airplane travels 3100 km at a speed of 7q2ht kmu+(:7 d-pflw w90 km/h , and then encounters a tailwind that boostsq tfw2dk: ul-(mp+ hw7 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 averaged t /ux* 9nvxj.-rwmelq wxsad5 9q9-( speed and average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed bysd /j*qtxxxvd.lwn9 m59w( 9e -qr a-u a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins atx7/7x 21nxybf3odel7. i kkbt the end of a bowlinbtn1 l o7xy.k/x b37kf2ie dx7g lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 kmkfjog-vjq(3ai8;c7(h. jx8 fch* wlq /h in 6.2 s. What is its average acceleration7 .c j*vg(qj-(fq8x3hfa8jic hwo; lk in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acceleration2c ng/4llky nx p+h5a 0wr-i0a + kx5parwhyl4 -lgac0in0 /2n
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particul(7su aa(njatk3mtipgqgaa8 wu,c: b *60u1j: ar automobile is capable of an acceleration of abou1 w,cpna :g(a:a3(ua0q sum8j*7tubi agt6jk t $1.6 m/s^2$ 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 iz y/+vcwe9.x bi5/p9udi 9li at then brakes and comes to a stop in 4.0 s, what is its epi+xauizicd95 bv ly/.w 99/ 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, iw8as: sy28ar which starts from rest at t = 0 and moves in a straight line, is given as a function of time 2i8 wyas:s8arin 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.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What .zb( eu:e l7dxwas its acceleration? How far did it travel in this time? Assume constant acceleration 7 x.u:edblze(.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its accerd7ic* wjbg* 1leration, assumed cond7cbj*g r*1iw stant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for taud w*xxk)otlmorh m39,.3l( bkeoff. How long a runway is needed if the (constant) acceleratio,(.*hb d wm ol)93k3omxx lrutn is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essrmf8 1e:)jgxua/*3ve j;bcohml42a-a /kysj entially top speed (of about 11.5 m/s) in the first 15.0 m of the race. W*amaeuj8fg:2yvh-kobjj 14 3cx/alsm; e /)r hat 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 10y.8:y pmknifaxl*iaw*i .q speed of 12.0 m/s to rest in 6.00 s. How far did itl1*m. .y ikapn:wf0a8yqi* ix travel in that time?    m

  In coming to a stop, a car leaves skid marks 8lnjhs abx:hl/e /0c 492 m long on the highway. Assuming a dec4ne:/0lc8xblhj/ ahs eleration 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.b )szq y.jjgquko(1s68 p;xq car compresses and the driver comes to rest after traveling 0.80 m. What was the s.gqyj qq);x(. obj8us16pk zaverage 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 init6s-m1+qb+ m qdd)zqou7c q8isial speed of 95 km/h and human reaction time of 1.0 s, for an qqqs d7mdub cs6q8) z+mo-1 i+acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation fojlkn90ee i 4,wiw;2qar 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’*9zs g c.d7 tx0axa6wys driver looks for an oppod 76a.t0xax*9z gyswcrtunity to pass, 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 t d bjx2o7s1a.ihe 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then accelerate at 0.20 xi21b.s oj7da $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h a903uc z md;pfvpproaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning z;9vcum3 d f0pred, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The 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 frue us4n;8 (k8hbgahu5fb .8ilom the top of a cliff. It hits the ground below after 3.25 s. How high iafkeh;. g8ibu48us lnuh 5b8( s the cliff?    m

  If a car rolls gently 0v+fxfvqg9artk v 5r:)ec0p cm;: pt4($v_0\,=\,0$) 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 :s/c)fc8pkp 7 r5;ycovf z4ooup 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 iwdh+:/s9h4t6y;z ;qmp1 y, lza;0kvezsq j jgt vertically upward. With what speed did he throw it, and what height did it r; m se ;szl 0hgqyzapj khd:q /6wyjt;9+v14,zeach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls underp;r4ubys5)p)+prqzul7- pr h 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 t)rb rzl5; +up7 qurpp4-)hpyso t = 5.00 s . Ignore air resistance.

A helicopter is ascendix q2enb* lc0+qng vertically with a speed of 5.20 m/s. At a height of 125 m0+lbqx* eqnc2 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 helicopter’s.] t =__ s

For an object falling freely from rest, show that tv;vqh k -pl(.uhe distance traveled during each successive second increases in thu.q kvlp;(v- he 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) that a balqo)j0/h jsm3) s-op9kptuux ) l thrown vertically upwar3h 90osqko/j-usp)m) jtx pu)d with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward 3m82jk1 l1 n ip,nfbwvwith 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 Fig1q7rm / rjshy8. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two app/r 8yj1q7mhs rle 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 2.2 m tall (Fig. 2–32)6j*w)qlayt j, . From what height above the top of l 6wqa,tj*y )jthe window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking tu9 ss0 rs0sy -*cfr-izhe ocean is heard 3.2 s later. If the speed of sound is 340 m/s , --0ssrs rsfc 09*uyizhow high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of waa,xh aso w/wc))sd7c0jf/p,bter. You point the nozzls/ sb,awxod,)ca0/pc f wh7j )e 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 verticall8u9g8 tnl kv:my upward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fut:kg8l8 9nmvig. 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 upwar0oz*0cq4rzrri sw3 6(a ,81fw ccjoigd by a window 28 m above the street with a vertical speed of 13 m/48 iow 0z rowrca(1f0 3j zr,*6scgcqis If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of time. (a) At what tdm5(gawq* d v8ime was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration consta5 8a(*ddm gqvwnt? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along5ox/bvk82i85w vwozn9 i ib.o a straight tunnel as a function of time is plotted in Fig. 259okoivb/zn.wibo vxw 858i2–28. 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 acce ka6 :zb:8xx0*urq pfrlerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots r*pa xf08:6rbx:qz ku in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in-yo:t q1t7l yp the previous Problem (Fig. 2–35) when it is in o7-1y lqtyp :t
(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 +3 eqn0pyl+wz traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object wh.ah 0ehkfb+ +l0yo9 fbwk6;qlose displacement as a function of time is given by Fig. 2bkqyh6.k+l 9f;ba +fwlho 0e0–28.

Figure 2–36 is a position versus time graph for the motion of an object alongu d6v; k4c u,+w1lp6ji devg0g 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 slo+djvg6 c,e6ui glk1w4;v0udp wing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-i:5ct 7v ev+db 9s*wzustory window 15.0 m above a firefighter’s safety net. The survivor stretches the nb*9ds :uc itz 5wev+v7et 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 tat hfhlr44)0ghe Moon is 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 would on Earth, assuming the same initial velocity?hrl a4)g04 htf

  A person who is properly constrained by an over-the-shoulde a19,*si:qja 7ywdn bwr seat belt has a good chance of surviving a car collisi aji71,qb: syaw9nw* don 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 bridge, 12 m above the road below, and his pg4,m8 cc k 4bvexr:3laee+3gdn i.r7i ursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that t8ei c:v ce4ggi.,xb 7dl 3m3erkarn +4he 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-end collisioneyy2c7pej ic i i+n4- wt.5hj,s by hauling them up on a crane and dropping them from a certa 4 j,te-y. 7+pw5ijcyih2 ceniin 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 travelsatwso4 u3v) q(a9q mu9y, nz;m /egijvvqr(9. 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 accelm m t6pgpy ibc0h3.744q/subteration 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 from where the front of the train started. What will my6pp/htmb 43qi7ct 0bu 4sg.be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a divi+ p-(shnj(awxz8xq 6n ng board 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.(+sp j8z nwq -n6hxx(a 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 tot6 a,i:bwnsw, balance the average speed of a train aiw :,awbts6 ,ngainst the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in 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 straigep( tpa,yhn4 /ht down when diving for fish. Suppose a pelican starts its dive from a height of 1/hp 4eny,t( ap6.0 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 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 plannh/*jswqb-s tpv+j-e 8ed so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assumh js s*pv et/qbj+-8-we 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 speed of 6.5h h8*stjt(2bpqucl6 0 2 *p ht8cht(6qslj5 ubm/s Just as an empty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high bui6u vkf sms0*u5q x6nu7lding. A second stone is dropped 1.50 s later. How far apart are the stones6mk5su7xn0uq6s* u f v when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trih 3ih2 6 9ss ekrtq6)zeb3emz:(s.;wl wvs3wjal lasting ten lapshs 6h)emqj ;we.wbte : lk323zz wrs6v9 si3s(. 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 Fraj6k uuv)4 -yslnce crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farthku v-4luys )j6er, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolinepf (5b ugscuq 1to2z.,s. The first child can bounce up one-and-a-haut(p.fgc1 bz, 5ou2qslf times higher than the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveli1gs9wn.oy lru*, nq1eng 95 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 traveled in this time? See Fig. 2–40. What are wuenl1*1,nsg yor.9 qthe 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 ofrd-7 zymww/-))g 3mmcmr6c rf 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throw)r -rrgmf-yw3c /mmzc )m67wd ing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accelpm/ cn(4g) wr/ pobyl9w9ad d/eration 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 intersectiev ipif d; qcm2n65yy3*4/uw ion has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west a; i/25 dcfpmyqvw 4i36i* euynt 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 constarl3 8au+k flf:nt 120 km/h takes off in hot3llk+ afu:8rf 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; 2.08) 2:/j(,tahmeu ntvz/vo+5mpyxu zw0 s after that, a second stone is thrown straight down ytzm5e )tj 8/w(2 u vzh/pmvn,+uax:owith 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 vertically up at the same time. The first stone is thro5/ ueuwn7t n6:r2,jr9 zwnx quwn with an initial velocity of 11.0 j znu ,qnu2xwe7:rn9wt5u6r /m/s from a 12th-floor 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 long would it take a free-falb 9mlt:evo-55znd mw ajz 3c,.m2uy;jling 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 s-c 3wmj5vzj,a5e;m :. nybzomt9du l2peed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers thqy0q (rpi4ksqn b+e(03o0cz drough a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apar3qd0 (c04q q(brisy+ zp o0kent, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertk8 9igvd fx 2i,msh-4 gdpv +:0+vjfyvically at a speed 1.5 times faster than Joe can. How many times higher will Bill’s balksv+ pi- y9vhfvd 8gjdi 0,vg4x2m+ f:l go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a clifw 3 5pin0,qkn4.m)koyfnqos 6 e:+lhpf while your friend stands on the ground below you. You drop a ball from rest and see that it take l3),.yqk6:nkfsi 0qh4p e+onpwmno 5s 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 hand. What is the speed with which your friend threw the ball?    m/s

  Two students are askedx: 2k99gxqw s1zw 5hxq to find the height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its 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 heightk g qwxxxq:1h9z9s5w2?    m

Figure 2–43 shows the po rdd3g-,p bkbny 5vk;xt5 r-9hc62mcisition vs. time 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 the other? (d) Whib ib ygd-5t6d k;v pc2r3xchr-nm,5k 9ch bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?