Does a car speedometer measure speed, velocity, orc6z99gtn i)o .4 iydbm both?

Can an object have a varying speed if its velof-kvxc 3 tmewv (qdk z817so/7city is constant? If yes, give exam f1/mw( vzxqko tk7c-87dsv3e ples.

When an object moves wh4+no b.8m/on af g-xp(j3d loith constant velocity, does its average velocity during any time interval differ from its instantaneous veloci( + p8m/a-obnhon 3xdo.j lfg4ty at any instant?

In drag racing, is it possible for the car with the greatest speed crossing the d5a,wdjv2a;1bn w il; 5 2na, ai vdbw;wld;1jfinish line to lose the race? Explain.

If one object has a greater speed than a second object, does theq :r(hbu + l 2*(bu1r7pyroclh first necessarily have a greater accel:qlhcrh+ub l*byrp( 2(71ruo eration? Explain, using examples.

Compare the acceleration of a motorcycle that acfuvwk(0n kjs32ru. (ocelerates from 80km/h to 90km/h with the acceleration okw (k o0(rj2s.v nuu3ff a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward ve cd+u*r3 bw1czxb)pe ,locity and a southward acceleration? Explain.

Can the velocity of an object be negative when its accwu0x*x rnyyz,6y nj 9 24aduu,eleration is positive? What about vicwx u62j x ,uyzudyy 4,n09*arne versa?

Give an example where both the velocity b d5m-oe9g te1and acceleration are negative.

Two cars emerge side by side from a t(.12 rdr5at85u7zsrsuviz yk unnel. 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 an58rsu. zd( rzuis7 try 15v2kad 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 increasinm* + hmh1d bnazg;b5 4b1fp)w2,gbz bxg in speed as its acceleration decreases? If so, give an example. If no+* 5);wmbzbg 4pfmxbh11 n, hdgabb2 zt, explain.

A baseball player hits a foul ball straight up into the air. It leaves the bat h9wor cbgt(8,p; 3u cx+ni/x6ux zkv2with a speed of 120km/h . In the absence of air resistance, how fast will thxk2bwz,nr x8c ogv(9+pi6; uux3ct/ h e ball be traveling when the catcher catches it?

As a freely falling object speeds up, + jqruc31xhim-qu 9(4mm eu1hy vl 39gwhat is happening to its acceleration due to gravity — does it increase, decrease, or stay the sam+-hl1m4mqj xqygue3m3(h9 c9 1ivu r ue?

How would you estimate the maximum ) 0,6d /lgx yg;- ltzpcxmxrs2height you could throw a ball vertically upward? How would youl/p tx xy;6zg-rd )m,g slc2x0 estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speep7v qhaby6h7) d 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 spee)hb7v7hq 6 yapd for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long verticafnn16q uojfbwd-0 e8bm3*m,s l string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falme1funno 0 -jf 8s,q36b m*dwbls 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 the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions3kdji py t:01;pi d8i.z8ybvu ai z3k/ is not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the wayta iz 1y kv:d3 jiui3;08p k/byzip8.d, a dish resting on a table?

An object that is thrown vertically upward a)cg5f btsh rc17() 5jp0upitwill return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, 5t5ht0j1cuc(gs7rp p bia)f) how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same tim;xq;6np hgbl e0 uz:.te? Give n 0p.zq;6:t lbheg; xuexamples.

Can an object have zero .xi7*4nqdiv*tem 8 qfxfo-+r acceleration and nonzero velocity at the same time? Give exampl i-mf.xir4x * n voq*+detf7q8es.

Describe in words the motion p :uo+,g 0mrhlclotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the moti+mr u0cg,lo:h on plotted by walking or moving your hand.]

Describe in words theu6/ ,+uue fwcw motion of the object graphed in Fig. 2–29.

  What must be your car’s ave4bjv o)7 zu)a+sd3ybbrage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it t q1u0jooa *ew6rtz)b +9i,qte5orlq*ake to fly 15 km?    h

  If you are driving along a straight road and you look to eg r42 kotqxyv) p+:*sl7lgt5the side for 2.0 s, how far do you travel during this inatt+yv4l)g*lptorq7g ext5 s2k:entive period?    m

  Convert 35 mi/h to a ib)qhrmp33z 55(lfi
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frolzqq1m 2k,uxk1 m :xv1m $x_1$ = 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 fo9koon;6phx+as u71 dj0ap .zwr 130 km. It then begins to 7d1wh0 pajxup 9aoz;o6+n.ks 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, es6 va:(-;0 -f admyvop0ihdepvery 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 essentiaav id-ea6-o0pp ;hy(f0 dsm:vlly 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(io 7 dyy52nrz time of 12.5 min. Calcul2dizyo7r(yn5 ate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straigclbl p6nf+0y1y j* ;rjht line, moving 116 m away in 14.0 s. It thyrln;y0*pblf 61j+c j en 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 tracks2w-e9 ff2zbo e. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach e2wfe2 zfob e-9ach other? (See Fig. 2–30).    min

  A car traveling 88 km/osx30*rp/b fdhk ) pr5h is 110 m behind a truck traveling How long will it take the car toso5r0bd rh*3)xppf k/ reach the truck?    s

  An airplane travels 3100 km at a soo82u b y ;y)nbu:v6vqpeed of 790 km/h , and then encounters a tailwind that boosts its spe8uboq :y nvoy6vu2);b ed 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 averrha7(g6rf o cc-2e5zv age velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunar5re2vz7oc 6hcg-( fch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with consth-swcd :t,)npant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound ocw,h)tp:- snd f the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 sm ( sfvij pw8x/8xs8rx.ty77y. What is its average acceleray8fpmxxr /7isv7j8(x .tyw 8stion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s inj2em2;: o9vm 6 neol7c2anfkj 1.35 s. What is her acceleration v 7o6eja29cnm:lnkje2 o2 f;m
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capab--j +v,g+s e my0hpuzlle of an acceleration of about g +-l0sem+vjz,-ph u y$1.6 m/s^2$ 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, peu4w2nssfq(l4 +1 h, ;2 vjkjmknqs.0 s. If it then brakes and comes to a stop in 4.0 s, what is its lk2w2q p4s4v;h+kmj,nj 1, qf uss( neacceleration 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 star r,7keam*)s zv5bz/ 2ykhb9uq)f*lgcts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velok)rmz9/,l2qkez* h75 b *gvsycfau b) city 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 3bkq35c.f,z5g:zr z b : sqhaowas its acceleration? How far did it travel in this time? Assume constant acce,g o.zqs533brz: cfbqh :k a5zleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. Wv f+x4iwc-dv+8:f hvmz t *by9hat was its accelerav4 *+yvm xctfbh:fi+w-d vz98tion, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How l jjoof.r/s+*7c 5l daqyu52g*jk jo;tong a runway is needed if the (constant) acceleration. 7 jcqs*agfl+ku/5j o;j *t5jyro2 od is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially to2bl ;n5d ypay,p speed (of about 11.5 m/s) in the first 15.5 a2l,y d;pbny0 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 spe5/ s8.hcd* pmi3)ey/ knp8kue7hdjiwt1y :vced of 12.0 m/s to rest in 6.00 s. How far dud t1//yevi38:i.8ny5dj hpms7*ekp c)hckw id it travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m b5snt;tgp2 az32p uq)long on the highway. Assuming a deceleratiab)up;qt g 22 n3tp5zson of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of thed*v rr2kj2./yy abcn fbc)c43 car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi 3 bc) f.nyd2ccrvykrba2/ *j4 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 stoppin/qb43 pdql7ez 1:v3 jv8v pidug distances for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, for an dv 33v l: bp1qpviu/z8j7d4qeacceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping d wes py1znv+,if 37am73uh j4yistance 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 driver looks foqq wdxl sf z90/o/o-q/r an opportunity to pass, guessing that hisoqz 9 //q -xwsfd/olq0 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 r gprrgx)86dc3,i* oo jun in less than 30.0 min. After exactly r,jg*x68dicro3 )p og 27.0 min, 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 car at 45 km/h approacy)y7ebwh j (*dhes an intersection just as 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 intej(y)hwy *d7 bersection (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. It hits the ground below afterj pu,6c534;p a ydowx 0zqky.g 3.25 s. Howjgox ,u;p dq p0yk4.3wc6y5 az high is the cliff?    m

  If a car rolls gentlyaqoupg 8zt,*583vl nh ($v_0\,=\,0$) 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 speed of 2;c7,g ax tqp4y,z v8iy2 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vertically upward. Wi )u v*ws-k;2 eenit3 q6c97qbpf)z mojth what speed did he throw it, an-pwn69t7qk )jqbe uec3o v2;ims)fz* d what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest andiel* 9)cb,hz e falls under the influence of gravity. Draw graphs of (a) its speed and (b) the dizh bci*le9)e ,stance it has 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 5.20 m/s. At a height ke*k o*u :4nybof 125 m above the Earth, a package is dropped from a window. How much time does it take for the packagn b*k*oyk 4e:ue to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the ad66q2v- *jmg c p46eec spbo9distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Gs4j map 96o2qv6eg*-bec6p dcalileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown 5f/ilbl0;r8cd tg- mz0 q eynbybd8,6vertically upward with a speed6bl,cy ; q i/gr5t0d0yb-8 fld nm8ebz $v_0$ 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 gnj)dh,13lsh 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.uir :0 dno)t4iiumdo:2-+si h 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the uncld rhoiiuiim:0t u-4no d2s:)+ear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2 03dt4qmn9e ga–32). From what height above the top of the window didegn0 dq3ma49t the stone fall?    m

  A rock is dropped from a sea cliff, and r.v;um:--hv/e 1xlkhz 0 shhothe sound of it striking the ocean is heard 3.2 s lahh h-vo;mvxe .-/0h:k 1zu rslter. If the 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 ouevodkunf7/lmyvtg; 9t5, qi0b27c . f water. You point the nozzle vertically upward at a 77 qdeot95t;cgv flubi02m k ,v/n.uy height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a8 +3 9t)iv jt9lpurutf noss(of;(t8q speed of 12.0 m/s from the edge of a cliff;n sfv)olt tt(uqr (ft99jo+8upi3 s8 70.0 m 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 ov3u6yy teho2)dpay:j l d5,+a window 28 m above the street with a vertical speed of)vo 5y6+oh3 tudpyj:d ,y ea2l 13 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 of a train as a function of time. (a) At xeskyy+2jp5si i 6 g-,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) Wsp ,ysj26ik-i5 y+xge hen was the magnitude of the acceleration greatest?

  The position of a rabbit * )wugc(k)i hbu to-3valong a straight tunnel as a function of time is plotted in Fig. 2–28. What is its instantaneous velvt)uu )(gh boi*ck3w-ocity
(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 ash4u7 3y gmccw3 shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the c u34hc3wmy7ggears.)
(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 s6(-do0t;molx/iq .4oeg t fg car in the previous Problem (Fig. 2–35) whfq;t4oem s.tg /-g(xd0 l6o oien it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object hcgzeo 9cz.3( traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose+; lgdvog4h4 k4 /lrl,,mapdo displacement as a function of time ,pd4l/arllodo g 4;v+kh 4gm ,is given by Fig. 2–28.

Figure 2–36 is a posixu0 vjlgmbxb(u/f2 c76c syk61llqy/(ifv;8tion versus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or 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 f lc1kls 6;bi/ c yfv6yb2(0gx/mu(x8vuj7qlquestions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’s safetbnwn fow;yk)9(5 g2e5llx8 okmcc0d1 y net. The survivor stretches the net 1.0 m before coming tl;kfonbo2lcx w5k)e850 (cm 9yn1wgdo 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 .phnun .a zt7-gravity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on.pt nz7h.-a nu 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-shoulder4v3 , tdhzsy5w seat belt has a good chance of survivis,3wvyt z54dh ng 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 on a brid*s+r5yg dql s+ge, 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 the tr5+ys d+sglq* ruck 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 test:6z3z(q x 57dv9qaffhrhtnms / br6r3 ed its cars for front-end collisions by hauling them up on a c3s6tzr: qxdfm3r a6 bq9n7(h/hz5 vfr rane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travejz 4i.p-cmtb,w gtmrf 712o: bls 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 ms 5cqv0bt*)arest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be ttm*5 a q0sbv)che 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 abovegqj mv-kd65w1r)cty: the water’s surface 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 whilety5wg) jd1kmvqr :-c6 under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit sya30(zo*0eai;qzd vpa na*3sn stem, it is necessary to balance the average speed of a train against the distance between stops. The moronaqas0 ndi a*z;p3ea v 0(z*3e 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 sn6k o 0txxd0g-sn(td+traight down when diving for fish. Suppose a pelican stn+ xdx06-tdnk og (0starts 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.    m

  In putting, the forcjgs7vn76f ms4;wog g+n ;e j.xe with which a golfer 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 ingjg47 ons;mx jg;fv7+s . ew6s 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 gfy w7zr+kh; c*0ku xq/2 +mr9mn ,xelconstant speed of 6.0 m/s Ju, g;kcmx7z q*fewxk0+ r2yu/ lnrmh9+st as an empty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high e.oofyu0ce 8.cenm 8;building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached.y;.8oefncc eeu08 o m a speed of 12.0 m/s ?    m

  A race car driver must +pt oeei 6ot.sad ,x.-average 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speedoe.-+pdxt eait 6.,os must be maintained for the last lap?    km/h

  A bicyclist in the Tour de Fr fzys4 fk8;f6ilx+h-p-b 8fvm ance crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 l6ffxsm8 -4p-v;8 yizk+ fbfhkm 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 play qk- j,/q8wl ul0xtn2ying on two trampolines. The first child can bounce up one-and-a-half times higher than the second child. The initial sp ,q8/ llynu-wtj0q2kxeed 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 travhpfxz( f5o9n 8w +u6t .m/rvwteling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. xpu hft.w5/nzmw+oft896vr( 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 throwinap 2zx0 6tzw8l -z.fv/agt(nkg the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, f a.z 6(k gt-tz0w nzp8vl2x/farom 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 verticr rzwu.r -7oaq4si;4lally, 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 sqlo+xs t, c1q gr9:9bohown in 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 in991:t,o+ rcxlq o qbsgtersection, 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 o1mun3d:6c ib120 km/h takes off in hot purd 1 buc:oim6n3suit. 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 that,whhb.,vuptjiem .*au j adg;f882h 2 , a second stone is thrown straight down with an initial speed o ia8u2,p th ;amwuh*f d8e2b. ,j.ghjvf 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same tim3bzj,n0jz(sx e. 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 stonez,s0j b (x3zjn 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 gtoiz+3vq,bwg 9as d6ree1r4 vt57 i,take 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 resistance will rev,6swa1rggbe,r 4t7ve tq 3 5i9oiz+dstrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to 2+ *m lxr0tnpdsend the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 2nptm0*x rd+l 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 fas, qav ni:p.2uh1roq: xter than Joe can. How many times higher wqix.vrnp 1q,ha o:2u:ill 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 ground be6m. aa; a/cv*+ bksez0(dgleulow you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below.(0au 6 e/b.kzava +d*ems g;cl 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 particular buildin:eiv1 grv -ir*g using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the ri- *ev:v rig1roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the ponv 83*p0c+rp bhml4ymsition vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Whichmb0hcn ylr 38*mvp 4+p bicycle has the higher average velocity?