Does a car speedometer me upfyez5:g6.r *dleyhs )mm27asure speed, velocity, or both?

Can an object have a varying speed if its velocity is cons60 7* kwyk2doz 5mgzxmtant? If yes, give exam mdy25 m*wzx6kgzo7k 0ples.

When an object moves with constanp.e:c/ u.:usc 7 jtqrp.xwas8 t velocity, does its average velocity during any time interva.erj pwx8u:ca7su / st.q:c. pl differ from its instantaneous velocity at any instant?

In drag racing, is it possible for th6ly/lskur6o 8 e car with the greatest speed crossing the finish line to lose the race? Exp y8 rlul6s/6oklain.

If one object has a greater speed than a second object, does the u/+reb8 qttyaf7y 6q80 .a z0mwi0y gefirst necessarily have a greater acceleration? E88ye ift/qyurgzambw6e.ya7qt +0 00xplain, using examples.

Compare the acceleration of a motorcycle thatwh828u. vkynr accelerates from 80km/h to 90km/h with the acceleration of a bicyclh.ywk2n vr88u e that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a souzbjs d ;6nng39thward acceleration? Explain.

Can the velocity of an object be negative when its acceleratiolxxv4wo1 r y 9ps2.g1kn is positive? What about vice versox1 vrl 4gyps1xw.9k 2a?

Give an example where both the velokqx q+vjyu526+q3cg29 qs hdwl- e/ar city and acceleration are negative.

Two cars emerge side by side,*k.(razfc2vgal3wa from 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 kkv(lac,. a2wag* fz3rm/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed a:nupl pck4s+o 05a wc sxnc57wd2h-a)s its acceleration decreases? If so, give an example. If not, s7h)s kp2nw4wodccp u-c:xa n l+a505explain.

A baseball player hits a foul ball straight up m)f*b/pxm w-p 11ei spinto the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catchexfw bes ipmmp p-)/11*s it?

As a freely falling object speeds up, what is hap0lf7e9 6kvkd vpening to its acceleration due to gravity — does it increase, d6v9v0kf dk7 elecrease, or stay the same?

How would you estimate the maximum4,.bzlrt*mn-a, xaz b height you could throw a ball vertically upward? How would you estimate the maximum speed you could givbb ,tzl4ma*n,. zr xa-e it?

You travel from pointdy n:7:*w-ku5k (f-tbllfy hg A to point B in a car moving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire d: *k(ut- f :ll-7hkwn5f gybytrip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts tied feb pp2(wl5) to dhvgq07 zt:5to 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 zg(5ftbw hd lp0:7q)v5otpe 2 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 i 7yhjt5,mqhm irlgbp,i5 dc8 l,i//3rs not at constant acceleration: a rock falling from a cliff, an elevator moving f m5hrgt, ,mic,ldli5/3r /b iphqy87jrom the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown verticallyglh2lon n u8d *q0h4x3 upward will return to its original position with the same speed as it had initially if air resistance is negligible. If aihun0 8q xlnl*43oh2gd r 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 velocity2r1m;bp5n a -)mlqi9on98d ysr9xad y and nonzero acceleration at the same time? Give example2 i a ;b qmda9m9 dr-s15)p9yy8rnxolns.

Can an object have zero acceleration and nonzero.z:u0( gz2rd vh 5y yi)hvp7bp velocity at the same time? Give z zuhyvvp7pd.25hg:r)bi y (0examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, eh1hvd c9l28y mtc. [Hint: First try to duplicate the motion plotted by walking or m8dc2 9vy1lmh hoving your hand.]

Describe in words the motion of the object graphed in Feheab b3idkl9a b4s c :*t,ejk5h0f2( ig. 2–29.

  What must be your car’s average speed in order to travel 235 .u7ylt 3owa -x d8an3jkm in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it tf+rm5zru v:6nm;5 uy(m/h*sam w:(ta2djr cdake to fly 15 km?    h

  If you are driving along a straz 47gzhm;g6jss.fli*n 0*y d sight road and you look to the side for 2.0 s, how far do you travel dur g.yizzjflhds;s6m7sg*40 n *ing this inattentive period?    m

  Convert 35 mi/h to ee*ikuxi+-3 k
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frpn : vi:hg-ld1om $x_1$ = 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 sc+ce v:uu, gt0y3 hqbpk5hm d6,hool steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after drib5u0p 6kqheh,vm:dty3u g, c+ ving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning flashh;u -+tyx/kzq12aso )t rcn8h and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arri1h r/q)s2+o n-tyh ct8kzu ;axves 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 track in a total time ok- )w;uv, qbxxf 12.5 min. Calcul ),xu q-bwvkx;ate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a sxr -g 74 ;h7g. trxhzjypv5yg,traight line, moving 116 m away in 14.0 s. It then t7y.;-h,7x gyr 4xgg pz5vth jrurns 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. Each has a d8vsq+(tywszo + y.m5a t-v0x,2oe paspeed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it qs ,8a.v+y(p5voayew t0x - d +o2mstzbe before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck a8ct.ldq)h )g traveling How long will it take the )8 qtaghlc .d)car to reach the truck?    s

  An airplane travels 3100 km at a speed e: :6y3q1f8 bmewzkizof 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800z:ife6b m: wyk8z3q1e 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 in whi/.t- . gozclv k5v/qejch the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch gl j/zvck-e./qt.o5v break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at the end of a bowlhe/h /j9y r.jqing lane 16.5 m long. The bowler hears the sound of /. 9hhjjrq/yethe 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 km/h i;qgka8z7 vdu:b6t * uan 6.2 s. What is its average acceleration in 7qk *bdv u 8aztg;6u:a$m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 7yef-jsz 7u; juw87iw10.0 m/s in 1.35 s. What is her accelerationj7jfy u7i-ew 7 w8z;us
(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 agj/m4.gqf mz7 i6 rm8gcceleration of abourgf8 46z .ij7mgm mgq/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 5n oqcar 1fx-;;cc9ud:.0 s. If it then brakes and comes to a stop in 4.0 u-xd;:f no1c;9rca cqs, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 /j,;zyt .hdgz and moves in a straight lt;zjz/g,y. hd ine, 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.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceleration? 6sy:0y lhx*m qbclok, b 3r1/aHow far did it travel in this time? Assua3* ysk l hyqxrbl:01,/6b mcome constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. Whu 7pmw4nxu 2,6phgc2i at was its acceleration, assumed concix, gn wu2h2pm6p4 u7stant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takj v 0y2v .qs8vjary.5keoff. How long a runway is needed if the (constant) acceleration 2svkajv850 j .yyv.qris $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed (oyp 0d355ke qkmbh+s6f f about 11sedkf 3bmp+k5y06 q5h.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 to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest inr .5 rqir:ur-t 6.00 s. How far did it tra5qr i.ru-rtr: vel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. ,q8efs 7o(8 ,jm1go- evfc undAssuming a decelerationf vu1cjfq78d 8e-g, ,n(mosoe of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h jp mo98ocf s11drbx45strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi j5c m 8bpo xo9d4r11sf on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 95; 5;ppts4 gttegi pjvg070+ytip4h0z km/h and human reaction time of 1.0 s, for an acceleratii p4 jp7tt p;es z iyg0h+v;ttgp0g405on
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distan tb1ohosvs/iomw*sy; 5*z 2- fce 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 dbyt-m y h3uz)wp(a;+d; 4nkpu river looks for an opportunity to pass, guh up(w; t-a+mb z);3ypynd ku4essing 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 le j 8t*dha9sief*0a 9ekc/j d,9 6nfuauss than 30.0 min. After exactly 27.0 0, *u9j/8seju in9 a*t9f d adfkea6hcmin, there are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her caa0sw3fr h;zn1 ip).bar at 45 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s befors ap13w.ha)fbin;z0r e turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light 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 f)j1n)lmgx6q3*dvo:ma dl t k,rom the top of a cliff. It hits the ground below after 3.25 s. How h6ja vt),mgndm1ql3 d )o:*x lkigh is the cliff?    m

  If a car rolls gently (l1jgi h-5+we q*r 6une$v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air with a s69mi e 7yvdx/rus:p(kpeed 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 hrkf7aiw -7)(1gvfub it vertically upward. With what speed did he throw it, and what height did iti7whvga (u7f-r 1kb) f reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw grapl eu9lee8nldc+)r 32 ouc7p)lhs of (a) its speed and (b) the distance it 3oenc)ll7ec +9 l82)dle upurhas fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of jall 20px8b;n5.20 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 g xp2nal0lb; 8jround? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance yu( : y,bt r3x(*a1wu+cwwhcd dc,pu8 traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shobx(d:8cwwp3drhy , 1 u,*w(utay ccu+wn by Galileo. See Figs. 2–18 and 2–21.

If air resistance is y+osbcgy.rz.u;j u jz :. *f4lneglected, show (algebraically) that a ball thrown vertically upward w:yu4c*j+o;.r g..sfljzy uz bith 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 with a spe0z*h p s4v2(ggh (bi,1cl iyqred 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 (or number mq- a;;zm6e lmof photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the a6mm;; -e mzlqunclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0/d/d3th0 vn)rp -g* izw,sqo n.28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above 3o v,z/w-) tspqg*/rn 0idhnd the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, anv 4f0gnh/q 4ibd the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is v4b0n igf/qh4the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of wd -ygjq ; olohag1,(u+c;)nppater. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the n;old gh ,)(c;u- jgppyqao+n 1ozzle 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 vertically upward with a speed of 12.0 m/s s0p: ,ihbw/uzfrom the edge of a cliff 70.0 m hig/ih s, z:puwb0h (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 upwa9qx-i :9h 6zps+ alzjrrd by a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown fz z6a+9qj 9:p -shlxirrom 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 funcg)5,yu*/.wxvhoh)fm 1ewmz3sc/ z uk tion of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceles5 yu3*/oghm/m u xk eh.c)ww),z1fvzration greatest?

  The position of a rabbit along a straight tunnel as a function of time is (e:sq9; egqzs plotted in Fig. 2–28. What is its instantangssqq :;ze(e 9eous 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 auto).v4k;* tjwriz *pwdkmobile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve)4w. v*kdw k*;jpitr z 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 u-b(syw 8o*6 n kq-lriacceleration of the car in the previous Problem (Fig. 2–35) wh*oqubi8 sylk6(w- r-nen 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, estimate1:yq x z/wgv,k the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t g)c12m(u k-yfejq-m -u ihv if7raph for the object whose displacement as a function of time is given b7vh 1qmi(yf-f ce)i-uuj km2- y Fig. 2–28.

Figure 2–36 is a position versus time graph for3 rnejuksd/k9 j 8o(n2 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 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 positive or negative direction? (e) Is the object speeding up 9rn28o3/ jkdk nuej(sor slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a fir 0 6lycwml(ke5efighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Figc6e5llw(m0 ky. 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 gravv) tvtf4-crk 9ity on the 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 samevk t)-f4t9 vrc initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt ha4 ;e:ei k/t rgxvl)m67*zzhk as a good chance of surviving a caxzi e*tza: v6)/he4mkg; 7r lkr 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 bridge, 12 m above the road below, and his gj9jbbpsp057 u4tcm xrk-z 8a3-i xi2 pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles 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 p49g8 xtspjbz-37-5m ribu0 jacixk2 many poles is it?    poles

  Suppose a car manufacturer tested its cars for ynk;1)f/xd d +zg,mwzfront-end collisions by hauling them up on a crane and drod1)fdyk /n, +wmgz;zx pping 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 about p g cn9v32et7qpn02 rv$10^9\,km$ 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 acdcoynz0l-iaymg( 0 /) c,n w8pceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who i many)0p,d-lzw icg (8o0 cn/ys standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface into a deeq 11 oib).u 3mlq/1sg:g1b wrv.utxbmp pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person whi/w l s) xqvrbt.1ouggbq m1 1m:b.3u1ile under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapidng99n,r k0yht transit system, it is necessary to balance the average speed on ,0ktygr99n hf 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 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 dm5di +0j(dvn6a: acw ziving for fish. 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 to escape? Assume the fish is at the surface of the water. icjwna+ z( a50d:6dmv    m

  In putting, the force with which a golfer7z; egr;/t okw:l.:w -wem t w;xht;gm strikes a ball is planned 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, assume that on a particul :w. oz;e;whgw ;eltm-k:r;tt/7gm w xar 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 tr w3ovt, zz:mw;aveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest awm , ozvtw3;:znd 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 6:79vrnzhk dzgg0 kk3of a high building. A second stone is dropped 1.50 s later. How far apart are the stones whenr9 k63kz vgdg0 z:hk7n 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 tr4whzie326 m/fm ll3k qial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for thql4h w eim3m z/32k6fle last lap?    km/h

  A bicyclist in the Tour de France crests s1urd2- 1i(iep ;bvbee5 k)yxa mountain pass as he moves at 18 km/h . At the botte-x5(vy ie ;)1 1pbuek srd2ibom, 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 playing on two trampolines. The first child can bounce up oe -wxbpao5v4cnk: )g :ne-and-a-half times higher than the second child. The initial speed up of the second child )5xc- nag:k4:wo bpev 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 overtajyz x j*b-a;:iwb3 5lzkes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed i;jzw*:x yb zl ji53-abs 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 throws a baseball with a speed of 44 m/s In throwing the basej0 p-as)diczhta 9bmz ; ik45)ball, 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 t4 bh)5kzzas;ij-9 c)ta ipmd0he average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertical1)wu/dulqtux :hn,ll f 60bx)ly, from rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each intersection has a tkgv62 :x /v b-tzedg)nraffic 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 greb e/g vdg)ntx 6z-vk2:en. 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 byxwl+( 25rdk h(ztup/(1 cbrhd a speeder traveling at a constant 120 km/h takes off iwz(p+c h(x51dhb/ 2rru tdk l(n 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 b5asb w d0:ig3that, a second stone is thrown str 3a5bd:0bsiwgaight 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 thrownq+nf b-gd7-m3z(q pdm vertically up at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should q gn7 pqbdf3( -m+-mdzthe 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 nn b2.xjub lclu ;:-q3free-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-:bq3ljcn lxuu. b2n ; her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conj649j5bx8euzzq-v r e veyor belt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production erzeq5jx 6z9vub -48j(in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball verticallg7/ ada-l j(xyfk8lj0 y at a speed 1.5 times faster than Joe can. How many times h0a(faljy/gk djl7 -8x igher 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 the groutkjk9 - s.bc7mnd below you. You drop a ball from rest and see that it takes 17 -bmj9t .ckks.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 asked to find the height of a particular6 3 ohxn3ni2dybv5x1n 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 diff53yibx3xvn2 n nh6 o1derence does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for j+ warb6v9p+vtwo 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 v+6vrbwa9 pj+bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?