Does a car speedometer measure speed, velocityoeymg* zei1keww 63+) , or both?

Can an object have a varying speed if its velocity is constant? b*d t/n;)eo -pf)k:x8u qqpqxIf yes, give exampldfpxqet8-:;) k*b qu)xnq / opes.

When an object moves with9 qh gl5t9d6gc constant velocity, does its average velocity during any time interv6gtc9hq 9 dgl5al differ from its instantaneous velocity at any instant?

In drag racing, is it possi n(fcn9 a.2d1g h sep1yobp*t)ble for the car with the greatest speed crossing the finish line to lose the fcgs1anp*2(o)p .bney1d9h trace? Explain.

If one object has a greater speed qww;0udq3hu79g c lf /than a second object, does the first necessarily have a greater accelerl9 qdq/3huuw7 ;cwg 0fation? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90km/hb;akg 9w0j d4x with the acceleration of a bicycle that accelerates from rest t9j;gd 0wa x4kbo 10km/h in the same time.

Can an object have a northward velocity and a southwa . -trw.hcrag+rd acceleration? Explain.

Can the velocity of an object be negative when its accelera(ttk v4- ryc93s thgl5tion is positive? What a t5tsvlt9y4- h ck(gr3bout vice versa?

Give an example where both the velocity and accelerati hm+jmkutj1waf(65 (hi/p 0byon are negative.

Two cars emerge side by side fromkg h* br,2r+aj ty/l.k 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 a/ak*b2+yh,.klr rj g tcceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasrxh;0d d2 ozb9ing in speed as its acceleration decreases? If so, give an example. If not2zxd 9bh0 d;or, explain.

A baseball player hits)emg(e/egs y *1vp.hu a foul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast p*gee1.(uev hmg)y/swill the ball be traveling when the catcher catches it?

As a freely falling object spet79bv/a 9 zrqaeds up, what is happening to its acceleration due to gravity — does it increase, decrease, or stay the s 97atqz9b /vraame?

How would you estimate the m 6wx/b 7jcm.4q60mhk wu0 drwcaximum height you could throw a ball vertically upward? How r x6bcudmhk 67.c /wmw00jwq4would you estimate the maximum speed you could give it?

You travel from point A to point B ina1 fiv )14vbbt a car moving at a constant speed of Then you travel the same distance from point B to another point C,v1ib4)bv f1 at 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 witodrh4z 0scx9 7h ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Whyhdc9o 07r4xz s? 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 acceleration:jfc/bpu sxn71x.x7,, ja duz( a rock falling from a cliff, an elevator moving from the pjjdacxux 71 .,zx u7(bfsn/,second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward*o ,awe mjp: 8wib3sf0 will return to its original position with the same speed as it had initially if air resistance is negligible. If air:m abw0i, *o3fj wsp8e 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 ac (yjm6r+hw3ef vs/3 b.vo7r cnceleration at the same time? Give exarn7hf+63oc.(bv y swvmr/je 3 mples.

Can an object have zero acceleration and nonzero velocity at the same tipka1imja4/9qb:bf f ;me? Give4ba;9/bqf jkm : ia1pf examples.

Describe in words the motion plotted in Fig. 2–28 is 5s zw3ja3pl;n terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or movsw; zp3l35j asing your hand.]

Describe in words the motion of the object graphed in Fig. 2–29 0h0grjtp :rm5.

  What must be your car’s avera;p-knnio(h- ,oqma 8kge speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long doessd) p9vj96:p d ql+cre it take to fly 15 km?    h

  If you are driving along a straight road and youlwkt8cm3om: dn- cq28 look to the side for 2.0 s, how fa :3lc8 mkmc2tq-dno8wr do you travel during this inattentive period?    m

  Convert 35 mi/h to .- sbosggh7hzm 2t, p4
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fro n5 pv oxpvfi1r7w.maz*e:n. n*(;l oym $x_1$ = 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 ubz4 b2jb7 wk;school steadily at 95 km/h for 130 km. It then begins to rain and yob ub 2k47b;zwju 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-thum5:4wq )id 4gu5reb a;5 jvg2xdrsn6s ab, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially nognqx r6a)5:2js; b5 siu4d4 vae dwg5r time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps a*.p afvrhlc(;eic jv9;qixu 5:m o1q1round a quarter-mile track in a total time of .fcjl1q xp5;*vvam ;(iurce9ho1 :iq 12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its traine p3cy p+ybj ;07l/edymr in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halppy/ ;cd0 7+be3 mlyjyfway 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 speed of +eeixg a;sn x-rp +v9/i/b/ bo95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach eacgx//ex+i b v 9br;i -soe/na+ph other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling H ix5vb+z ze57nl8hp+g ow long will it take the car to re7eiplz5+z8nxvh 5g +bach the truck?    s

  An airplane travels 316srg(-5 m akx6gdzo 7s00 km at a speed of 790 km/h , and then encounters a tailwind that 6m5s sgxzo6( 7rdagk-boosts its speed to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average v p4w/ce/3oqd aelocity of a complete round-trip in which the outgoing 250 km i //d e4qco3wpas covered at 95 km/h followed 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 pins at the endj iz;c-r vlwj233v-e8xaye3 b of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.5vcljv2jebxz3r 3-ai e3y; -8w0 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 in 6.2 s. What in5) mb9tt*f;zkix .k vs its average accelemkf;vtx .tkn9*b)z i5ration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from res n d-*3bey(npqt to 10.0 m/s in 1.35 s. What is her acceleration (np -3bdye n*q
(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 ad 6w nh99y*o,eswo6xjcceleration of aboue6hwyos,*onxw 6 9 9djt $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s. If it * dad 7o6i:v-5xhrp nwthen brakes and comes to a stop in 4.0 s, what is its acce6 d pna*hor 7-:v5xiwdleration 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, whi iujd9 .((mxhq8i/ng wch starts from rest at t = 0 and moves in a straight line, iugiq9h. xm(wj(/8ni ds 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 itlkwib(:lv2 ,ac g4 : oifa+h2hs acceleration? How far did it travel in this time? Assume constant acceleratio2ca f kal+o2 hgb:i(vi:,w4lhn.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of-vn(xd ;bim.b 85 m. What was its acceleration, assumed constant?x(bvb.;mn i -d    $m/s^2$

  A light plane must reach l)3ll tvp+xt vejrdtqff931i)e 18(da speed of 33 m/s for takeoff. How long a runway is needed if the (constantjtf)18t3dtllvfl+v 1 3rid(e)p9x qe ) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst x7j d7. i br)n2 nff:wny;zc:pout of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What)c wy: dnn j:pfzxirnf27 7b.; 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 in 6.00gi m9/ nmvp.:y,, fhmi s. How far did it travel in thatfh9ynm,i, pi mm: vg./ time?    m

  In coming to a stop, a car leavn rgw 1xz(95bles skid marks 92 m long on the highway. Assuming wxg 9(15 rnzbla deceleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h st 2u jrn1;8azc9tzlu0 trikes 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 cj 9t 0cra21;8ztnzuulollisi 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 km/bn5wz819 chanh and human reaction time of 1.0 s, fo5nwzna18 c bh9r an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping diszz95 ;r) 5znnd0vla rstance 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 d ivi86je -ad5priver looks for an opportunity t58p6aj dvi -eio 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 the 1 8(c(o0vdh6 z:vo8.mp cnl 9xia7hcsk0,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then acce :apcn9 d6cv7. ox8h(iozl(8shvc 0 mklerate 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,f)7d+uwee71 ny1rkol k6gkyx7 d l4v the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum decel7eu x kd71 d)6gwely k7,f+14konry vleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground below af/u35 yhnm5fb uter 3.25 s. How high is the clinf5/ y5hu mu3bff?    m

  If a car rolls gently+ojxl v2te+h oqe8-+u ($v_0\,=\,0$) 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 i ktxp2+(* n s;z*zwdptnto 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 t m6od5j g0zcy4 svuj8zk2l61bhrowing it vertically upward. With what speed did he throw it, and what u52msz l 60vb1 kjgd86zc o4jyheight did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the inppggn r+lv )ftv1s.q5kg2.2n fluence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function s1l.pg) .f5 2n+tgvrv2gnpq k 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. At a height of 127dub(mjk( 63fubz ( ro5 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’d u7b(b (3j mkuof6z(rs initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance travel9gmzz wla.- 4ged during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This.lg9gzw4m -az was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, sq*hh38jmy/wu t/m,;fou g *xbhow (algebraically) that a ball thrown vertically upward with a oq,uh fmb*/;3 /xm*8 gwjhtyuspeed $v_0$ 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 of j(-t+ wum6os*/tc8*w yzbqr jt1p5 ey18.0 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 betweehc4dv eodx,14qo sq/* 9tss v:n each photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Ads,tx s4o:v v /ed49s1 qhc*qossume 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 t kze 8.45cgsq.*rob/ m9+jwj4elv qmpast a window 2.2 m tall (Fig. 2–32). From wt+mjb el e./v8z .*swk9cjrmqo4 g54qhat height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, ant v zhdu 3257+yadbypj1q d1-ld the sound of it striking the ocean is heard 3.2 sd13 qybj5+up 2- l7t1ddavzyh later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose no n:z 2pmha9r/zzzle 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 leaves thzpz n:m/2arh9 e nozzle?    m/s

  A stone is thrown vertically upward with a 1 pk4s;q,ab zmspeed of 12.0 m/s from the edge of a cliff 70.0 m hi,sqamb k4z; p1gh (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the sta8bq,e-z4nw;l 0bh.shui+b k-tn t (areet with a vertical speed of l(wib. u;h ,bht-+atqn 08n4e k-bzsa13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity hb) rgq-z *7.s/6rmct r-erw wof a train as a function of time. (a) At what time was its velotg)w.rze -bqr*6r rc- /m7s whcity 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 time is p7xeaxia-yvw cv,d)67 lotted in Fig. i 6,ay a7cv)v7x wed-x2–28. What is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

  In Fig. 2–28,
(a) during what time periods, if any, is the velocity constant? t =    s to t $\approx$    s
(b) At what time is the velocity greatest? t =    s
(c) At what time, if any, is the velocity zero? t =    s
(d) Does the object move in one direction or in both directions during the time shown?

  A certain type of automobile can accelerate approximately as shown vw;k4u u5d7bd in the velocity–time graph of Fig7 kd;5u4 dvuwb. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average accele:;n7jj)dz2kx: b h aawration of the car in the previous Problem (Fig. 2–35) when it ):h;nj7bz x a :kw2jadis 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 q voj:u5u7+m ski nfm2c: a2z8traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graphzrq7gn2vyu )f(mc435jxg vb 5 for the object whose displacement as a function of time is giveny2uvfmgg)r3 5z nv 75j(qcx 4b by Fig. 2–28.

Figure 2–36 is a posik041 l5z1nkgvp leyk; tion versus time graph for the motion of an object along the x ax41y;z n1klglp 0vk 5keis. 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 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 fo2g+rf5wtl avast .ydo- mm00sx80ig+j 93mbxurth-story window 15.0 m above a firefighter’s safety net. The ss +wtf8o m9 m as+gx-0b i2lvmax0djygr5t0.3urvivor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sixth what it is on Ear i))cvhnim( 7rth. If an object is thrown vertically upward on the Moon, how many times higher wicrivi hnm7))( ll it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has 8pva: p 2z3ywia good chance of surviving a car collision if the deceleration does not exceed vw2yp zp:a8i3about 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 pui:uw44) askddrsuers 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.4ikswa)4u d :d 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 hauli kp* ,9/xhq63kc eqxudng them up on a crane and dropping them from a certain height. 9he kqx 3*6ud cxq,p/k
(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 aboutrg7 cih*tn2/ui jdn99s/; o8c0z grp w $10^9\,km$ 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. Th kqmu1o+u60u( i vh:bze front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car asu06iqo+:uu( h b zvmk1 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 i;43 gt1hd 5jqdqdl-m pgq+ 9nento a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of q gmd1 d 93n qqd;5jglh4+-tepthe person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to bala.hip (dy 0lk-m(z:f kd72qvponce 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 train to make a 9.0-km tri ql2k7 f dkpz.y(ip: -hd0v(omp 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 f4uww ux6* tvx6e :1vy n6hgf0yor fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it t0 uunt:e1*wy6vvxy wx4g6h f6akes 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 sbdi6db3o vn+ m/ 0ymd-:kodp: trikes 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. Accomplo3n0v :+miykdd d m/6dbbo-:pishing 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 co stft) 3y.nx4uals+8 hnstant speed of 6.0 m/s Just as an empty box car passes him, the fugitive+8x4lft.h y st)u3n sa 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 te3)i-.n gjs6zr wbeq f -pw58ohe roof of a high building. A second stone is dropped 1.50 s later. How far apart arp5wn rgb.s) f-83e 6zoqeij-we 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 coq3p 4orc 4jq7smjsyj; -7fuv3urse of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what avera3sq4u 7;fj p rj4cjqvs3y-7om ge speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de 5q q ka 9t k/duf1l..*daopqn+France crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 kmnkqf/p1.lauq9 o*d dt. 5qk a+ 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 onn,y-4 4 1er he5 xc-cofo)fgcne-and-a-half times higher than the second child. The initial egreoc54cn-cff h 4, 1o) -ynxspeed 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 )nffpwe;;flwud.zn4b92 *m fu w ,+hktraveling in the same direction on a track parallel to the road. If thewf*dz2u +mn9hww; ;,ne4 k)ff.plf bu 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 throws a baseball with a speed of 44 m/s In throwing the 3b hk f;gsmo0w( s lr;1q:xhn*w-z,kbbaseball, the pitcher accelerates the ball through a disp,s(b 3h -b;o:;xkzwm* khsn0rwf l 1qglacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleration octsa-x td( 1xptbnp4i;5 d )o(t8r.v 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 inf9y4xed22x;gi mef: q 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 green. The lights are green for 13 s each. f ;df 9x2g:yi4emex2q
(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 con:m l( uqy1 ut56uv/ddfstant 120 km/h takes off in hot pursuit. The police officer catches up to the speedmu/u(ydf: tu 61dl 5vqer 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 vg btfzry9) 5;that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at5)v gfry ;9bzt 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 u u/y c:zfjph706s rac6p 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 a0f: czupj 66c/shyr7and 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 resistam;:o,w ew;(cxkcla nz* /t ciw6, b+mgnce, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an g ;6+ebxan, c zc o;wwi:mt *m/w(c,klaltitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant sxqi 9 .ann4;um.vjc 6qzd1zyjm k1;2uses a conveyor belt to send the burgers through a grilling machine. If the grilling machine iz.vn;qs 2y;u 1nz j.qkjamx1 46 di9cms 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 times faster tmqbl4hr ) kibw19d(.ahan Joe can. How many times higkbabh)9(rm iw4qld. 1her will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while yourus7w y m/)srt4 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 jwrs7t)/ 4ymusust 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 t6- j) il7h ad;kpv1a3 rurwe3qhe height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timi3)urk7pjwv6d 1-3 eqhaari;l ng 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 bicycle+p;m7g m8zq lks, A and B. (a) Is there any instant at which the two l +kmpgmq8;7z 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?