Does a car speedometer measure speed, velocity, or boz mzp,d t))lf/th?

Can an object have a varying speed if its velocity is constant? If yes, give n/kk1a1uk*je* n2rrl examples1*1 2rkjrln/kuea * nk.

When an object moves with constant:v0zgums15zh7jt 7svf eqf 0s. 6s*pi velocity, does its average velocity during any time interval iv7f usjp * 5vsf:meg0.0t1 h6szsz7qdiffer from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest sai j jcj9p7nb9 ); ,q3r6uwmimpeed crossing the fim,u cpr m iw3jji9n;a)79bq 6jnish line to lose the race? Explain.

If one object has a greater speed than a second object, does the b 7i lv*lw6:jz.wj(lcfirst necessarily have a greater acceleration? Explain, using ejivl * c (jw:lz7bw6l.xamples.

Compare the acceleration of a motorcycle that accelerates b:ldae2c )3br from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in tr b )eadb2:c3lhe same time.

Can an object have a northward velocity and a southward accelerat osz:er:8o6+k vws/q pi8ok 7jzqbg-po /9tm+ion? Explain.

Can the velocity of an object be negative when its acceleration is positive2 arte:hfu82kqbvm:y nt262p? What about vicf:hvan22ykuqm2 :8 btr te6p2 e versa?

Give an example where both the velocity asrm7)/j mm2ah1cwn:end acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is t+hkg4;+z*rwsjmegll0uh+- d raveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnedzu4jrk++gl s- lg0w hhe*m+;l? Explain your reasoning.

Can an object be increasing in spee(a 5g o 9xstl3+qqz4cyd as its acceleration decreases? If so, give an example. If not, explai3 ( yqx+9cq4tao s5zlgn.

A baseball player hits a foul ball straight up into the a7hj,ufh l bej450kh7rir. It leaves the bat with a speed of 120km/h . In the absej,ku f lr hh07j74ehb5nce of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds)lt6mrzhyp zxkg(,* *l (t gx: up, what is happening to its acceleration due to gravitylp**lx(:) xt(t6gzzhym k, gr — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw ig 83;n6trrkia ball vertically upward? How t; ri 6rn3gik8would you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed of Tq 3 e:zl.hw*nfhen you travel the wzfn.:q3e*lhsame 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 demonstration, a 3.0-m-long vertical string with ten bolts tied 7.pl)yov7s rdto it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of thpo7sdvr y .7)le fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant accelepydd)/3 m9 kx:3bvbah ration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, pk3:ab/d9)bdymx3v h a dish resting on a table?

An object that is thrown vertically upward will ret ztuwsi-4r0v2 urn to its original position with the same speed as it had initially if air resistansrvt- 42ui wz0ce 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 velope2ox ndhn+;4 city and nonzero acceleration at the same time? Give ex 42+phd e;noxnamples.

Can an object have zero acceleration and nonzero velocity at tm p -m-0wvbl9mqmg0e1 he same time? Give examples.0w1lbe m-9m m0q-pmg v

Describe in words the motion plott q1 e2,vo,salied in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicol21a iv s,qe,ate the motion plotted by walking or moving your hand.]

Describe in words the motion of the obdzf 4o:oh/lo4ject graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.253 i9ata)f,rak h?    km/h

  A bird can fly 25 km/h How lip , s arrd,uui/e.+7 j(oxbp,ong does it take to fly 15 km?    h

  If you are driving along a straigyt5gq1; c7dayl, p/j qht road and you look to the side for 2.0 s, how far1/c ,la;jqq 5gpdyyt7 do you travel during this inattentive period?    m

  Convert 35 mi/h to iwp8ash;:i;ew fj z9wmw- .)b
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fromr0jb 8lzazo i-h8 49pv $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

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

  You are driving home from school steadily at 95 km/h for 130 km. It then begsu;5 m,vo:(ky -pxclx ins ;-pv5yxs,l(xu kmc :oto rain and you slow to 65 km/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 lightning fl+ -pd z.4pvdxbash and the following thunder gives the distance 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 thi-d4x pbp dzv+.s rule.    m/s

  A person jogs eight complete laps ap7kw 4/s mrq7lround a quarter-mile track in a total time of 12.5 min. Calculak7sp q7lw4rm /te
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a strai3w xv-r;qsmi*1 d udx)ght line, moving 116 m away in 14.*i 1x);srwumdqx 3-vd0 s. It then 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. Each has a spe5kqwvzy27lx qjh42d jof a3f wo4172red of 95 km/2 5d4qjqwvx71o37jhl 2y f4rozaw 2k fh 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 kmm:fo7i 3rig* h/h is 110 m behind a truck traveling How long will it take the car to reach the tru3*7:ihmo r figck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a tailwj3fm47 ajy :faind that boosts its speeda7fy ma:4f j3j to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity 6eavf6/xq:6 og;eup h of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at :6qgu6xhf;vepoe a/655 km/h.    km/h

  A bowling ball traveling with constant speed hits the 67jr ks ,h6qsztomhry3j5v4; pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s aftqs;smrto j6zk,y76 hhjv435r er 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 acceleraj6pl*k(ca4g8pp : .wi bq; mbxtes from rest to 95 km/h in 6.2 s. What is its average acceleratioqp4:p(j 6kcglxw.ib*a pb8 ;mn in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10ns:pt*n* jn t;.0 m/s in 1.35 s. What is her acceleration ;:j np**sttnn
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automo ls0.qb:8l pyq/n o+kwbile is capable of an acceleration of aboutbl08 qply.k nw+o :/sq $1.6 m/s^2$ 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 twcu) q.fhnjhk /dnj:s,0 -oz;ravels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.uohf0)qws:;d j/z.n,cnk h-j 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 from rest at t =6-9wyi )bu )z4s8d8ekgws4nh9p d vhi 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleug-ew8n4 iz ih )kvdyp6 s99)whb sd48ration 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. v5ef/.ejdj56jmkjl qn l658 vp0a1my What was its acceleration? How far did it travel in tj50e5qk6f6 1edlnljp y8.vmjma /5 jvhis time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distang3 cmwa6zd4utigh - jmh/80(h ce of 85 m. What was its acceleration, assumm8a(ti34 j zhhg0 gmc/ -whdu6ed constant?    $m/s^2$

  A light plane must reach a / )a58w//bsygyk f;zryyi p -mspeed of 33 m/s for takeoff. How long a runway is neeyaf/wz yks /5-y8)p/; yigbm rded if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blo kw6t (j,lme:q(xxn/mcks to essentially top speed (of about 11.5 m/s) in the first: e(m(qxktnm6l x /j,w 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 frorayb ym6 89t5dm a speed of 12.0 m/s to rest in 6.00 s. How far did it trav9b58rtd yamy6el in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assuming 7u 5l(c/ rioima d7( i5mouil/rc eceleration 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 ofrj2 2gpjr 3 :+map.t+ pbc*m-tvfx;ym the car compresses and the driver comes to rest amr y:m3ctvpfj gj.rpabt p 2;-+2*m x+fter traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed o4n)tr h/qztdn;n v 5bptv;w* 6f 95 km/h and human reaction time of 1.0 s, for aqhnbtr 4*v 6zt ;)n;d vptw5n/n acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation forn42n /9sxsnb u,on+9kj c.lzx 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 highwnwo(un-ic, u0 vrn)4 xay. The car’s driver looks for an opp)n4(rwx0vu ,o unic-nortunity 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 sld*z ps 2xo/1the 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 acs*xo/1 z s2dplcelerate 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 ao1ozn 0y) to,ts the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the inter oz,t01otyn)osection (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 from the top of a cliff. It7sfr d hp0m*-i hits the ground below after 3.25 s. How high is the id-rf*hp sm07cliff?    m

  If a car rolls gentlyf f rj.916yxjaxxf8o 7 ($v_0\,=\,0$) 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 wit+/(y*k*g ehg9y,qyk()fwcsbi l2 y7akhs 0n lh 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 i+ *p z6agge5fkt vertically upward. With what speed did he throw it, and what height did it rea+5fp6zk g*g aech?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the ; py/s :b7tuv g(-vsswinfluence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a functionugpvv; /tby(s :s7s -w of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. Attshq 8v+h-s ntm4fs65 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 gt6 n vhsts5 f8ms-qh4+round? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from/a ;pr6ip* mbhq)k 9*+bfnkqh rest, show that the distance traveled during each successi;6a/f h)mr 9kp b*i+qbhp*nqkve second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown ver t4pdrha45wcd z*lwk02wfo2n d s(n-(tically unrp2sfk*d 4o5d(hzw40wcn (ad2t lw-pward 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 with a speee f3o+ er*c.a +fst3:lpgf. hud 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 betwe ua.l/p,ovvl (e*j p6een each photoflash of the apple in Fig. 2–18 (or number of photoflashes p olp uvj/6a( e*,.plveer second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel d*bo uv9tt .(,m d.k ptom ,06ymulbd+c43uv cpast a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did tv+ mbblu cd(ott 9ok,*p. v.,mcd6 ymu4d 30uthe stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the oojm(5ju 83qtl +gwtn4 cean is heard 3.2 s later. If th34 w+ goqutjjnlm5(8te speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You point osv2d*2c 3jyq,e y7gn 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 spe22 y se7yqdg,v3njoc*ed as it leaves the nozzle?    m/s

  A stone is thrown verticallbyjwl6(r fx+oy4l-f 2en) h4ky upward with a speed of 12.0 m/s from the edge of a cliff 70.0 m426k wl b)fjhrlfeyn4yo-x (+ high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m abkns2 do *vf*3dove the street with a vertical speed of 13 m/s If the 2k*ov df*snd3ball 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. (fn* a88kdgtp6 a) At what time was its velocity greatest? (b) During what periods, if any, was th6 k*88gdfn ptae 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 fj237 kn1: ukbd7 2ma5knoylj irl-1yqunction of time is plotted in Fig. 2–28. What is its instantaneous velocl lryuykikb 2 -5nq:jja1d 7o312n7 kmity
(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 accelerpv 1h) ws+cdeh1 zn; 4)pfhd)adyuhp;,+ 2vacate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)fdhzp2sapp1 1an4h)+d w)yeu+vd;,;hv )chc
(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 the previous Prowt/azc cr7m2i/,o /t bblem (Fig. 2–35) whezc/rt/ba2tc/o ,m 7win 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 the1yt7ox i-snj 3 object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the objectc 6+6 qowqwx:a whose displacement as a function of time is given bo 6ww6c:qa xq+y Fig. 2–28.

Figure 2–36 is a position versus time graph fin,id,p :-h.aij mek6or the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positi ,aikmidp j-:en6.h,ive 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 or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story wo6o jecyw7 v: x f8;l+cv.8qooindow 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37o8qv oxjoe8yvfc ;l+. wco7 :6.
(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 grvj72oreuu0a2zfo btu 450ap y9 fml;/:5zg t uavity on the Moon is about one-sixth what it is on Earth. of;o5aauj7:95 veuzm2t lfzr gu20y bt4 0pu/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?

  A person who is properly constrained by an over-the-l::js r t, 0 fqcd8:tzp sbfny/)7f2ceshoulder seat belt has a good chance of surv t) jez80cycdf:,tf2fs7npqs:b: l/riving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing uogj7y 9 9e8ios3v+j2p. pj foon a bridge, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of t+je j j9 f3uygois pv.o9o8p72he 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 colliar;y4uy h.e)ut79tj vsions by hauling them up on a crane and dropping them fro vh9ut7jt; yy .)ru4eam 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 c pgnu 2-q5io m0bmo:*about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from rest. The front of oq r8zpg(e ; jpyh+ju3yl 42t8nza;a. the train has a speed of 25 m/s when it passes aayp 8qyt; 3o;jlha r84 ep zg(jnzu.+2 railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surfap 9vna nq-/ pe2ciu4e5ce into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person whiv2ni5eae cqu94/p- pnle under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necls;/*;(8t7 tho4 xyy 4ystfbtq 1ycilessary 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 l; q1cyyho ;(tytl4*fs/4x 7s 8tytbian 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 pd;8i-2nd t5y-pf xwch4t6pr diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path orpt2nt;6fc -8idw p py xdh4-5nce 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 planned so that th-m2y*(c3.g rmoy ra rze ball will stop within some small distance of the cup, say, 1.0 m long or shoraymryrzr 3-c o* 2mg.(t, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at a constant s on41i;.h1y mgmce2 itpeed of 6.0 m/s Just as an empty box car passes him, the fugitive sti g1i2nth.4mc me;1 oyarts 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 dropped an(bz fk1y*/k a mz*b+,9h yxy1.n,*y (k mba/a 1h*+byy xfk9zz50 s later. How far apart are the stones 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 trial lastidmv8u pby87 7sng ten laps. If the first nine laps were done at 198.0 km/h . what average speed musty 8sdpm77b 8vu be maintained for the last lap?    km/h

  A bicyclist in the Tour de France1 0ujxm i/n2*lsyt.dg crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 ksxyu/.*2m j l1ti0dgnm 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 onent v*tm r8 zuw6vr-(b)hxv569y(is jc-and-a-half times higher than the second child. The initial speed up of the second child is rv i*b-t zyj wvr6s8u96xnm5 t) hcv(($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 e 159iikfyosjj cv21 x tgx,2: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 9sv:xjyexg1 2 5kj2fotic1, ipass 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 45xvk9jx- zwh j-6x vjwith a speed of 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 poik-hvj6x 4jjwxx5zv 9-nt where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accelerati-jrp3 sp/z r+lon 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. Ey xi:el7-m j4f kv1wb1ach intersection has a traffic wiyxlk :7vj-f1ebm14 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 green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120 km/w gcs,2w igtig 0fo/,7h takes off in hot pursuit. The police officer catches cgggiso ,w,w/0 i7 2ftup 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 rhn;l2l8sau nfle7-1 5bh cv n;oof of a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the twon2 ls le1u cbah 5-vf8;lnh;7n 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 * )-d:,-jivs9zgbw ef n uqoy/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 the second stone be thrown fru -de:/zbgj-yiv w sfo*9n)q, om 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 tae+ui3stal/n,qj q/ p 2ke a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistaets2,3 iuqnqj/ p/+ alnce will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses ad )rxjefl955rvs6kk5 conveyor belt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5fjx)k 6lv s rred9555k 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 times faster than Joe can. How m b-yuyo4m9t c:any times higher will Bill’s ballu4yb 9:t -ymco go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while j 3cixyg fof7)mv4j4co6og-q m)aq30 your friend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed withf a 34 jcy) mg coq4-jo63v7qgfm0x)io which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular(ja dbon5 ya-4 building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the b4do (aan5byj -uilding and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicp :uwu.6p +pa0dyeb;dycles, A and B. (a) Is there a6.p e0uby;dp: dwp u+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 highest instantaneous velocity? (e) Which bicycle has the higher average velocity?