Does a car speedometer measure speed, velocityv4d28fz3fj hpv8-la n , or both?

Can an object have a varying speed if its velocity is constant? Io4tu(l;13gjj:sni vk f yes, give exampl l3v ;o:t (g4s1kinjujes.

When an object moves with constant velocity, does its average velocityqy0 epk6tc ce +c2 ;yuwy32+iz during any time interval differ from its instantaneous veloccezw ci+u;2c3kqy0y6+ p2e ytity at any instant?

In drag racing, is it possible for the car with thohsd8(fi); *jc8pl /r: lgsyme greatest speed crossing the finish line to lose th)g/mc(ri*8jdo f sp;ylh 8 sl:e race? Explain.

If one object has a greater speed than a sec w0tpdu:(pq:i5u* mlz ond object, does the first necessarily have a gred:um:w 5upz0iql*(ptater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90km//jpo2uz1 nq7g ye:w -fj -6togh with the acceleration of a bicycle that accelerates from rest to 10km/h in the same ti zwjftog-n6- uj/ p1o2qge:7yme.

Can an object have a northward velocity and a sou2* qiah8bx)zj, mwsrz91ns3 gthward acceleration? Explain.

Can the velocity of an object be 9x1 js twfv19j6tq f+rnegative when its acceleration is positive? What about vice versa?+t69jqr 1swf j19v ftx

Give an example where both theld+:hyu 6k-a-di*xih hz. ee0 velocity and acceleration are negative.

Two cars emerge side by side fr vdjir32-*yc hom 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 h -i* ycdr2v3jthe tunnel? Explain your reasoning.

Can an object be increasing in speed as yf7bhk1j 0 xm o-,*qorits acceleration decreases? If so, give an exajxr*kmh7yqfo b , 1-0omple. If not, explain.

A baseball player hits a foul ball straig c:lp*y k2gha- 85sjlxht up into the air. It leaves the bat with a speed of 120km/h . In the absence of air j g5l8s y :lkxh-pa2*cresistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its acceleration due)(jzimphmdb3f p6r00 ,lt9ihk:t6u k tz3:)6fr,ipml960t(d 0hukk hijpm bto gravity — does it increase, decrease, or stay the same?

How would you estimate the maximum heiv jdcej :tal ,b*g )y8pcb;k/9ght you could throw a ball vertically upward? How would you estimate the maximum speeal; bve/py,*jj)d8g kb ct 9:cd you could give it?

You travel from point A to point B in a car myqqe8w0).mnnurbpn ns, )1hoo v t:75oving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h)v,owy8r 5pqhmb n7 n)0n:sq.oue 1tn . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-lonyh4tvkp6.i9g g 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 pgyvk94 i.6th plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant accey(kxfd159r ns leration: a rock falling from a c1 r9k5sf (xydnliff, 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 upward wilun-)tctw( y w+nfs/ *ql return to its original position with the same speed as it had iniynt nc/ -suwf+*t()qwtially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration ayyk;u9,ii sg4l. g2ryt the same time? Give exrk yg9 i4gy.2l;ys,ui amples.

Can an object have zero acceleration and nonzero velowvasct 8yt**sf*kjgle )9 i*6 city at the same time? Give examp8 *6cf*w9vt*)se iak* jylgstles.

Describe in words the motion plotted in Fig. 2–28 in2/vdfj r 04bnk terms of v, a, etc. [Hint: First try to duplicate the motion plottfrj2 kdb0vn/4 ed by walking or moving your hand.]

Describe in words the motion of 8;rn0n khdh/oz ;eu*f the object graphed in Fig. 2–29.

  What must be your car’s average speed in ordon1n 7zfh bm91.ie xb:womm*8er to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fllw p568bdm4z7ktzbhokr(rs4 s,xb xz:) x0n)y 15 km?    h

  If you are driving along a straight road and you look to the side fk6z gcrkmh /llw36pr; qn -:v:or 2.0 s, hkl6 pngc:/-rhq z l;v:r 6m3wkow far do you travel during this inattentive period?    m

  Convert 35 mi/h to kl8ia yx8nex mph )595; 7plny
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from f7xfvi g)6mh( $x_1$ = 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 stead)eev3+96e qaso sy9wo ily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home aft9 o qoa 96eys)e+3veswer 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 01trthd099o otr*oqy3odahz86yck, seconds between a lightning flash and the following thunder gives the y o rc0 dad1ot0hkorth99y t*6,q o38zdistance 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 around a quarter-mil)8tib ;jkklq/uv1,b w e track in a total time of 12.5 min. Calculaqv8; )bk jui, kt1l/wbte
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a strr38si0 8jb56tceb bqvhn hi(,aight line, moving 116 m away in 14.0 s. It then6, r0se b(q8b5vcb 8i3iht nhj turns abruptly and 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 other on parallel tracks. Eacqt z5q/ o ( jehm(la03ac2f(ivh has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apvq 5 fizm/3 (lo2caa0(h(ejtq art, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m bex f3he2 96kfnlhind a truck traveling How long will it take t l 63ef9hfxnk2he car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounteaso)2ol5yjq3 9 uixr *rs a tailwind that boosts its speed to 990 km/h for the 3 5iju)2aolqr*9sxyo 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 +iq n5zie mbdd);eq/.a complete round-trip in which the outgoing 250 km is covered at 95 km/h f5m.d+e/e nq)dbi;iq z ollowed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pinc iu 45 z2/e)eah-sgxss 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 relea4gsc-) i hs 2a/ux5eezsed from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates fromygc 2qc/z- w+k vi)zf9 rest to 95 km/h in 6.2 s. What is its average acceleratio2cfiwqk9/c- g)yz+ vzn in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest gn:/joo/ olyj e:y-i59bz: g jto 10.0 m/s in 1.35 s. What is her accelerationo /5 :ojl9yn g:-:bez g/ojyij
(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 a*7 muzy5uh ok9241 do9xrb)ldfnb 9wln acceleration of abou4uz9 u 5dh1wo7d9n yfr)9lbl* m2oxbkt $1.6 m/s^2$ 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 consd*hnvw f 2d0p6fc- m/rtant speed travels 110 m in 5.0 s. If it then brakes and comes -26dw/ cfhm*fpv0drn to a stop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts f)plaa4 nz(gk/kr5 3 zxrom rest at t = 0 and moves in a straight line, is given as a function of time in the followin)krxaaz/g4(p3 5 nklz g 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 m)jrz :0r)* xxe m5evpq9 i*k* cvv3lmto 25 m/s in 6.0 s. What was its acceleration? How far didjmxclz3)* ierv*m9 epqmv0krx 5): v* it travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s tdx /uu; vj)xxpa3m t3+(6hpi: ok )emeo rest in a distance of 85 m. What was its acceleration, assumed const:/6)etmp dvxuk3x(xj+ 3moh uei )ap;ant?    $m/s^2$

  A light plane must reac*,dwg g*ftw* s7euv +yh a speed of 33 m/s for takeoff. How long a runway is needed if the (cond*7sg+,gvueftw * wy *stant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst )3dlv0ho(bn wout of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her t3 n)lov b(w0dho reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from5+d8 tzw u8o4lhxxi2d a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that tiohtd xw825+uzd4x8 l ime?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assuma m:td9 o ho *)(:4uplgq0nrefing a dec )qatrgn4:loo:0m 9 *pe u(dfheleration 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 ca iczd( abyxn,+*m/)rzr compresses and the driver comes to rest after traveling 0.80 m. What was the average accelb/my n(r)cad*z+,xi zeration 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 spe;mwt8r+n o3ub:9lpn q ed of 95 km/h and human reaction time of 1.0 s, for an ac 3bm+nrqnoul8wp9;t :celeration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance of a car is x;8/+wtknyu10n-w l- ievn+l9 ak cqe$d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , 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/:d+6nb h( vbxpp+tsh)) fb wj;s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car can accelerate at 1.0sxvw6)+ h+t;npf b( )d b:jhbp $m/s^2$ 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,-k hhnf9)ha /h6 p/xfc000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then akn fx- 6cphh9)hhf/ a/ccelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection just as tybobxjjo5 0 g9sh2 g.q.a*i o;h 7p;yyhe 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 shyj7 o. yj2b5xh*bi p sqhog.09oa g;;ye 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 r pm(zojh)b5 j f 09glqo(m+2bthe ground below after 3.25 s0f(jhpbq o2 bo+mgrm)l5j9 (z. How high is the cliff?    m

  If a car rolls gently ltyyf8e7b , m+($v_0\,=\,0$) 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 ne sobp yimkz+(-k/n 1e+arly 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 after throwing it vertically upward. With whs1o00m +v vo;x48;iu lezx ephat speed ;i0lo+v xm1h uxo p04 vs;zee8did he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Drawg 0qa1uk1x fp9 graphs of (a) its speed and (b) the distance it ha0kx1 1af9u qpgs fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascen1 t vw3z6v1kfjding vertically with 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 for the package to reach the ground? [Hint: The package’s initial speed equals v6vwkf3 j1tz 1the helicopter’s.] t =__ s

For an object falling freely from rest, show that the diste *f,,/oglai* op5zz zance traveled during each successive second increases in the ratio of successivz*afe , * o/5gizzlo,pe 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) thatkgyi177pzegf6m b;u z/g )p l7 a ball thrown vertically upward with a s/e1 gp6 fgzk) lu7b7z7; impgypeed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed 0ewj.(pmi a:ch;i6l h7 vlsa/ 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. n(- x z-favvp,ky4lz62–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear onenla-,f4kxzpz6 (-v yv s at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tag4ijfvi/o:db )ej7 i *ll (Fig. 2–32). From what height abo egf j b7/*vj4id:)iiove the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it strik7j mg 352azj +n716nazmruolling the ocean is heard 3.2nl2mo5z1j7 g 7mz6a3 +lau jrn s later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your gakdn7j9*y53meqku y k ,rden hose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). 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 le 7qkkmeu5n9*y3d,jky aves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 1khom(fs*g8 yn(br rh*jh r192 2.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34gh so 8*rm19(h kf*b(rh2 jnry).
(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 t0f95ur w0ro dwindow 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from thf 0o50 r9wdrtue 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 fu2i oh6qoei/l3 nction of time. (a) At what time was its 6 iio 2h/3eloqvelocity 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 acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of:dj/6/ avpbayl(w yoo7s) w4q time is plotted in Fig. 2–28. What is its instants(a vb)pqo//wadw ly :6jy7o 4aneous 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 lm2*t) vgz*guz z+yk2 the velocity–time graph of Fig. 2–35. (The short fzgu* v)yz2tmk*2l+gz lat 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 gahh p: 2zq +wj+yr.i:the car in the previous Problem (Fig. 2–35) wr2a+p zi h+hwqgy:j:.hen 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 the object dy mhhhm ;7afn;4s;5mtraveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the ob97vq hd mab1n91i6 icpject whose displacement as a function of time is given by Figp1n1vb 9 cimq97d6ah i. 2–28.

Figure 2–36 is a posic8 raa8tva1q z*,me nuo ,ln2-tion versus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or nega88tn *muv l ,1o2nczaqa,r- eative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a;tk 5na6 4dthq fourth-story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m beakt tq;5h n46dfore 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 w wq0sg7a3j9j0m)e zb 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, assumiqs wj 93eba0jm7)wg 0zng the same initial velocity?

  A person who is prop +nyiej5s 0v4m9mo7n( rio;o gerly constrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the decevr;gs9 nmeji 7no0+4oyi5m (o leration 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 brcqemi)61/mu p3/c*r f g kzdf2idge, 12 m above the road below, and his pursuers are getting too close for comfort. dcqg*6/u2izr )mkmp1c/e3 f f He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond 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 by haulinxws7)nczw )s;(o vb6 gg thenv;b )wwogsz 7xs 6()cm 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 tzfuf2z71ce s7y5lnc qzma08 4x/vs c)ravels 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 acceleraml 2pz+*5s-b elysi g1tion 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 tryz m*1l 5sbe2is-+ glpain started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s)rv.qlc: hyghmhh.3 kc5v,t9 surface into a deep pool. The person’hhchtl9h5qv3, )r.cv.:ymgks downward motion stops 2.0 m below the surface of the 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 transizqhy31a8jmyu2vq1 7x t system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a traiquhv2ymz 1y18aq7xj 3n 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 straight down when diving for fish. Su jwk5unz o.swid 1.d:(ppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If id(i:w.1odz k.u wns j5t 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 striknc/*)ko5h9 zc)x; qk ivvazw-es a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, ihkc9ozkz5/vxw)a v n;- q) *cin 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 fr8(k)k 71 lrl;ahi6rwv tnk q5jeight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, t tk(nlq5 jr;8r167iawlv kk) hhe 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 building. A second stone is droppedpmb;u2 0vjv08p thh)d 1.50 s later. How far apart are the stones when the second one ;tu)28bpp v0 h0jd vhmhas reached a speed of 12.0 m/s ?    m

  A race car driver must averan y0p.)fgox2ir,qwi6 7y yzv7 ge 200.0 km/h over the course of a time trial lasting ten laps. If the first nine xy.7v0yqz76,pw iiy2nf o rg )laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at 18 km2 byhfde)nt8v:+ wi-rbe/ui */h . At thtnb :*w)2+befeur-iv/ y8i dhe bottom, 4.0 km farther, 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 playin7:dk7s- jz7hph si7 bc*gpd8ng on two trampolines. The first child can bounce up one-and-a-half times higher than the second child. The ini7 * bp7hdc8pd7nzjshgi- 7sk:tial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train traveling in lz1pszg7h vnb,:tj n2h104yvthe same directivhhj,bn2 sgy4l0zpnz1 7v : t1on on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are 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 throwsegp79cea ;o x- a baseball with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball throu e9e7ca;-gp oxgh a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from r9l b/wr(z)bo sbz,hm0 85bqs zest, 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 htq llvp*- 3hi.8h4 ff *zv4jiin Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn grezv* th*hi4lijv .f38 l 4-hfqpen. 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 takesm- naw*7*hawa off in hot pursuit. The police officer catches up to ah7ww *am*an- 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 c2i n6ha1xzz v 9me5x0roof of a building; 2.00 s after that, a second stone is thrown5zvn01cxx9ze 26imh a straight down 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 vertically up at the same time. The first stone is d iv(y*w vr8wy-tm8*j* k k2r nwp9ru.thrown with an 2yr*wmwr 9( 8np iud-v kr*.tjkv w*y8initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial 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-fallin9sj**v:c9nz q)acpswo7zu mt) ,x2kp g parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speedtm**o:7asz)s9zp2cjvp nx) kw uc9q , 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 cony5os o7ae lp( ,+b(aglveyor belt to send the burgers through a grilling machine. If the grilling machine is le (ag,+(ysapoo5l b7 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 tiqrigk;ax;z/k1 pzl m psucamd:t 1q+1,/r (i7mes faster than Joe can. How many times higher will Bill’s ball go tharlmk+ ;m :cx1gzd;1r/ /i,u1 zktaq7ppsi (qan Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground bel2 ;yzivo 5t+mcow you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your fvc;oz y+im5 2triend 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 to find tcn(kd+9 77a. mnpdy85y k tktqhe height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof otkp79 k7.dm(+t5c8n dynayq kf 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. t3 bdbk9 at4xxwh4,2qlime 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) Which bicycle has the hixaq4lh d3t wk9b,b4x2 ghest instantaneous velocity? (e) Which bicycle has the higher average velocity?