Does a car speedometer measure speed, velocity, 4y3df .pqk7a6p8 y7nsp x5kusor both?

Can an object have a varying speed if its velocity is constant? If yes, )sfar34efq ou ;sqa4 ye::le: give examp)a:qe4 su;f ql:e43 e f:aosyrles.

When an object moves with coi*)o4y ,fg laynstant velocity, does its average velocity during any time interval dif4*ag)l,yo yif fer from its instantaneous velocity at any instant?

In drag racing, is it possible for the carugq q4bms1dm/h rd9tz/2z* 8q with the greatest speed crossing the finish line to lose the race? Explainm*md/zhb1z9/ts gquq dq r482 .

If one object has a greater speed than a secondn3a 0wx z*h8tu object, does the first necessarily have a greater acceleration? Explain, using exampl0 wa3*xt hu8nzes.

Compare the acceleration of a motorcycle thaix k(do+v+c1xfsx. b 2t accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the samx1o+ x(sxvc2+fkbdi .e time.

Can an object have aqyovkm.pntc07veas+j sf* 4+ *7oy+ v northward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? mwhczj 3*h *(c ya o/8+mbr*wyWhat aboutycy *w (zjw8m3h*ho*c +/mr ba vice versa?

Give an example where both the velocity and acceleratil l2ur,*lpcz 3a/shr 7on are negative.

Two cars emerge side by side from ld 2ppcwje bbj;r(/;7a tunnel. Car A is traveling with a speed of 60km/h and has 2 rbdc7(bj/jpe l p;w;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 tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If sog +5cw o*iap *ihrb:l6ls9cs*, give an example. If not,* bo*s+h6 5slrcg ia:liwpc *9 explain.

A baseball player hits a foul ball straight up ime+z x4p*5z qinto the air. It leaves the bat with a speed of 120km/4mz*eq+pi x 5zh . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds7r2 xe 9k uctr(jqwi;2 up, what is happening to its acceleration due to gravity — doesx 2qtk;er9c j(7rwiu 2 it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertic,/pig5dp b;p 3aw+dw ;acv n*xally upward? How would you estimate the maximum speed you could give itdxd* 3 a aw,pbv5;+wi/; gnpcp?

You travel from point A to point B in a car moving at a yg;q q8-gt/ zijfn;5 rconstant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.jgirqz;nft8 g y/q-;5

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts tiqku+2 u)wrm( ded to it at equal intervals is dropped from the ceiling of the lecture hall.ukum +q(rd w2) 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 the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at con 7y6hsq7z+e xdstant acceleration: a rock falling from a cliff, an elevator movin qe7+7xshz6ydg from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward wz dw )f6w-z i,znjyd,+ill return to its original position with the,-yw zzd)wi d+,fjzn6 same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleratio;xa(148 rixm2hgnph tfd7x8. y, pxvnn at the same time? Givem .;(2x pp,xhtrv axdf8478xyn hni1g examples.

Can an object have zero accelera .x)pm3wh5x 0wa uru.ntion and nonzero velocity at the same time? Give examplerm.xwu nhua0w .px3)5 s.

Describe in words the motion plotted in Fig. 2–28 in terms of /:ygxe:z tv,gv, a, etc. [Hint: First try to duplicate the motion plotted by walkiggtx,::ve/zy ng or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–29. uql d07vw-k9 e7vai( 3)adel z

  What must be your car’s a2em p3-m9rdfbz6nfg ygv ua,o( g:a54verage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to flyzs.+otaue4yh 3x o +d* 15 km?    h

  If you are driving along a straight road and you look to the side fovvuqk 06c+9 luz;58rx.p9hr 1ojkj uor 2.0 s, how far do you travel +ljukuq vj r 59poux01 6.89ok czhvr;during this inattentive period?    m

  Convert 35 mi/h to :bd(2azj//yywxbmese6:mf s f. d1 z5
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves0jxnef f5ost0*0v 8lr from $x_1$ = 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 92c)nd4n0-em2e hzc m j5 km/h for 130 km. It then begins to rain and you slow to 65 kmm nehd2ezjn)c0- m 42c/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, eve:k yl5 u/lhb0ury five seconds between a lightning flash and the following thunder gives the distance to the flash ku:/hyu50l lbin miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in nrr7dt1pw m )em61n8va total time of 12.5 min. Calculne6m18mtnwd ) p1v7rrate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trains phtq*hj +gk2,t 7otmn8bi80er in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calcula8h ts+qk,0 t hbt7nipm28ogj *te
(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 trackstd,i49 hz0 rq.jjz; rb. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, hoz;, 9q4tj0 . rizjhrdbw long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How long wbgc4fss+ 8 k t9jncm66ill it take the m6g+ s9jkf4 8b6cstcncar to reach the truck?    s

  An airplane travels 3100 km at a speed oc/z 668tprk6 k3h;nihnd es2 of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 28003;h6erk pi czt6/nkho6 8s2 nd km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of y96ae i j**ow2 nmu0lla 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 returnla mu j o**6e0w9iyl2n 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at the end oiawb52s : 7xr(ny vid7f a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released fd5r by iv:xi27awns7(rom his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates*vbnui0dkt(a3/5 ob n/vz l*b from rest to 95 km/h in 6.2 s. What is its average accel*nv v i*b/50kt db3aozu lb(n/eration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her lj 4*h0bn(r9 ea8;6usjr wqzoacceleration baehr l 409 r*;z8jq (jusonw6
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobn:/u0h g+ikp vile is capable of an acceleration of abouv:g0 iu knp+h/t $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s. If it then brakes +qx4e bejcxpq7w:w 9 c9+5tmtandt79+c ewb jq qmpt 4c+x9wx:5e comes to a stop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t5;os wt2bdex( = 0 and moves in a straight line, is( 2 s;obdtewx5 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/*j: c yco8uc(ls to 25 m/s in 6.0 s. What was its acceleration? How :*c 8yuoclc(jfar did it travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/ss)9s zwl9 19u f(rn8vlu2jnrr to rest in a distance of 85 m. What was its acceleration, assumed cons1v9f 98rjl)r s(nsl9 wrn uuz2tant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway is neewb k90ifqn 0(ided if the (constant) acceleration k f0in 9(bq0iwis $3.0 m/s^2$ ?    m

  A world-class sprinter can*)i 9ls :s49v z*psc-hjdunxr burst out of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her tsps:d* jxi* vs -9uh)c94r zlno reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a.qibe7ig eb7 / speed of 12.0 m/s to rest in 6.00 s. How far did itgqb7i ei.7/be travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m3lcf -ck)eiz m/ f9r refaa8(4 long on the highway. Assuming a decele4cm/)( rafe9a r3 kfifce8zl -ration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strik6t,2wbzkymh wca x 7:2es 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 collisiawh k y,mx7w2:tc6b2z 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 spej- fd/r,f. jired of 95 km/h and human reactrj/ -j,.f dfirion time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for yuho nylq8:-s 7 1:0mfkitpp 7the 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 highway. The car’s driver looks for 73j.w a,aqekcan opportunity to pass, guessingq, aj3cwek7.a that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 min. After exjuhv82-0x-jz h wj 0wsactly 27.0 min, there are still 1100 m to go. Twjzvs wh80 -xh j-j20uhe 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 approaches an intersection just as the.zg/ n mwu 1zt-l6ppg ft)+;nk 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). mw-f t npg6zg.)pt/1lu;k+znShould 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 thevcg /7v:wm) wacg40m e ground below after 3.25 s. How high is the clivwa0)4 7vm/w gcmcg: eff?    m

  If a car rolls gently ( 0hdbmb ph o-82,w(mfi$v_0\,=\,0$) 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 upyne2m 6+:ps 2ff rr1cq into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s afte3d5xgpva o6 w*r throwing it vertically upward. With what speed didogda p536wvx * he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity sdcvn m42l 2ytmd 7 n5yv9)onax +:u4mfov-e+. Draw graphs of (aocand y4n9 7-:m5smvdye x v+ mvtfo22nl4u)+) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending wmlmcsrc -- 1*vertically with a speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reac-wcmlm s -*1rch the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling*l lavn:k oqhd9y. r6: freely from rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, e6h *::lkv9ny ldqoar.tc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is negleceif*mhp. udh -xu1- okb2ih1-ted, show (algebraically) that a ball thrown vertically upwai-2fd p.h*kh--1 1eohimbxuu rd 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 vertic m azf bzc2xw(:js9a29ally upward with a speed 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 eacpyq:mb w7j; wlzu3 r0,h photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 1qb: ;wyj3wm l0,7purz0 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 past a windj xduc ; ;y6x)vj)6qamow 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone fall? 6dj;mu;a )y)jq6 xxcv   m

  A rock is dropped from a sea cliff, and the soun 0/z.3 yfipfatd of it striking the ocean is heard 3.2 s laterf3f/ z.py i0at. 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 o ++,hvqbm7yc qf 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 vbmq, yq++7h cwater speed as it leaves the nozzle?    m/s

  A stone is thrown vertically up35b izww7kg 6cu9vx: cward with a speed of 12.0 m/s from the edge of a cliff 70.0 m3 9x6 bz cui5v7:wgcwk 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 wikqu z jqn;m8o/)p.a4yndow 28 m above the street with a vertical speed ofpo q/ kjq; a8u4.nm)zy 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 velo6ql:4n rtry8icity of a train as a function of time. (a) At what time was its velocity greatest? (b) Duringqr6l84itrn y : 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 t2d j -l7oxqd.y9m,upgunnel as a function of time is plotted in Fig. 2–28. What is its instantaneous velocity d,x dy. -mpl7 o2jgu9q
(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 acceaj, /lcmx+a,d b1n(wnlerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short (wl d1 na+jxbanc/,m,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 acceleration of the ca8mvt2zma77g zd6-wq x r in the previous Problem (Fig. 2–35) when it is in gm6vtwzd277amqx8 z-
(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 tylk4uy0j-(r pqv oa.*raveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacea :) tvwdq7:psc6qg (lment as a function of time is given by Fig. wvpd():qqclsgta6: 72–28.

Figure 2–36 is a position versus tvztq5 nm,o-3xudv*s :ime 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 5us3vvzd -:ox nm, q*ttime 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 window 15.0 m above a htjl2u2)d973qm 4he93 t ;tszusbu pifirefighter’s safety net. The survivor stret)43e;it9mu2tpq7l zs 3udhsh u29jbt ches 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 gravi:.ea5yw o(p7hf:eosmty on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?y .p(m5hfoe: s:w ea7o

  A person who is properly constrained by an over-the-shoulder seat belt has s. ftk3axbpb 4a k4in2 aa**d7a good chance of ssif xpa4kb3 tbk74d n2a* a.*aurviving 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 bridge, 12 m above the n c:s (5zq-cstroad below, and his pursuers are getting too close for comfort. He -s:(c czqst5n spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisnq5z )xcz/fl wyt,a )+ions by hauling them ya x /5)ftq,c)lw+znzup on a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth p0r* ttcsn8p)travels 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 theji pa-x+; d 8p2:shf6hhqm/zo;g;j uf train has a speed of 25 m/s when it passes a railway worker who is standing 180 m dmx2jph; a;-hp qf/;sf8:j+g6zuh io 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 abzi ;n:hrkv ki;k :3.pjove the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below zr.: ; ;:khinvkk3pj ithe surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transi-ug69 mrwl o;st system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.09ruwg;los6 m- -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 (m:ydl y -0vyu6mdu 8sdiving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasiu-yvlu :6 mm(dy0y8dsve 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 stri16kk,,dfvi mc1fj *ofcd)yhglh )z)( kes 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 co i*zv)cfk) 6f1(y,,dghj1 mhlk )df 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 fftnou*u: 3 ve dlq9y +jake7s4( 8(vstreight train traveling at a constant speed of 6.0 m/s Just ufq:ae3y (9eovt *uklsvj7 8+( s4tdn 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 building. A secj*dj* tc3r )5omoltbkgqeb+zo5-q7 4ond stone is dropped 1.50 s later. How far apart are the stones when thqet m 4k b-)gzo+r td7j*jb 3oo*qc55le second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the cours 64qcsx0id:4hra1t3i*mzh pue of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintaiirqi4 pu zsa 0c3 t*:hx16h4mdned for the last lap?    km/h

  A bicyclist in the To5p;1g nfu bzi*ur de France crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his spe z1*fpginu ;5bed 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 trampoliu-ezxx0fej*tz9 s+ b pf 8r1+63qrhscnes. The first child can bounce up one-and-a-half times highef hsz6rz9e1s+rx+*08cjpxu f -etq3b r than the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h ovc*:jizt/oaf0q gs,rl/ 9 1h wpertakes 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 pass it, and how far will the car have traveled inq1s watfo: 9/h*piljcg0, r/z 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 throwin 8sh1;d3ywkui p:kh( ( hgxz:qg the baseball, the pitcher accelerates th:s hy(dik puq(8wkg1:hx;3h ze ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from*c d(j lryzp f5,d1ah0z8j8as rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each intersectionqo cch3 ilqkd/-zh;rox,0+ 4 u has a traffic signal, and the speed limit is 50 km/s . Suppoihqz3,;d+ -k4oholcxu 0c q/rse 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 120tc:+1q ;axu7yy:ofjp5;n+kxo gr jg- km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant acceleration. n j:ptx7 ;c :u-o g;aygoxr+5+fyq1kj
(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, a secondt.6.ie)se szg stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same )g. sizsete.6 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 emk(d9d 27owoefd2b w l:o p2u8jf10stime. The first stone is thrown with a ed f:w92do2 (uop7f8l2j0d esb1kwmon 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 from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-falling paran10f;f39 y oufjmz z/nchutist 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 anf y; zf 0931j/mzuonft 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to se,0mcay t:us75mqbd1gwdj 8d5*6vyt end the burgers through a grilling machine. If the grilling machine is 1.11 dmd jqtb e50 w*v6syutya:c5m8,gd7 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 l d572)rb tbte1k 8p* ue*gxy91htscnvertically at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go 8 1yetgdu lxkn*t7 r 1ebc)2sh5t9*bpthan Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while;nypti7/zfa (kjdu)/ your friend stands on the ground below you. You drop a ball from rest and see ;/zjtiu (7dn /ay kp)fthat 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 with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular building using anm. vmpbu c(gk yey *3r*r)4 b+-h3tbo /fwyv. barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall tim t 3m4* r. yn/pc(f ye* yh-3ogv.wv)ubm+rbbke 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*dlyj:* enn0 2hxg: +5wz0hoo ame-daw uf4e- 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) Whicndaa-d o+u0wn0-*:xe2e 4ezj wh5glmf :ho* yh bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?