Does a car speedometer measure speed, velocity1wvt m -gfhl3/, or both?

Can an object have a varying speed if its velocity is constant? If yes, give e3d mck3 he4jte -z5s/lxamplesk/ js3et3edz-m c4l 5h.

When an object moves with constwa r )c*5c3sbdzsiv)7t (wan. ant velocity, does its average velocity during any time interval differ from its instantaneous velocity at any inswnwvb)5 .sa3st(7cadcz i) *rtant?

In drag racing, is it puaxs ee k17cy4 5fu(:j+koy29z4l (mohije 5rossible for the car with the greatest speed crossing the finisa5 k e (1e :zluuyoj4f49ij mcr7h+k5s yx(e2oh line to lose the race? Explain.

If one object has a greater se :pwc 3nmg:x.peed than a second object, does the first necessarily have a greater acceleration? Explaemp::nwxg. 3cin, using examples.

Compare the acceleration of a motorcycle that accelerates frm0dlu5c(*.)aoo9de e wpg chzh .lh.2 om 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest td0c wocl*2.u dm pe)ea9h.(gzhh.o5lo 10km/h in the same time.

Can an object have a northward g.d tk*pe8u q.0vckg8velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its accelh0mmd2si+bdm( b 2vfw/e e70teration is positive? What about vice vew2mvm+ei2 07dbf s0edh(bt/ mrsa?

Give an example where botnlvi6 *x xfa,*h the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling wit;jsr sw1u-lt4*hu 2rnh a speed of 60km/h and has an acceleration hr *ws tu12jsn4rl-u ;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 decrease60uhj ,qxah6gwdf h, ote +//ds? If so, give an example. If not, explain.h6 ,/j e6ghw /dqo+fxa0hutd,

A baseball player hits a foul ball*a kb;n) 9 *u4g kmrjqv8:jrcq straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling whearcqj *b; nk kqj* mug:94)r8vn the catcher catches it?

As a freely falling object speeds up, what is happening to its a i yii)nu./ox,cceleration due to graviti/)i, y x.nuioy — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a bal3l5pc7bpi h- eh3) lobd 2pb:zl vertically upward? How would you estimat7i2pzllb3d5oh3ep -b :)bhc p e the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed of The6ot ;ww) .uxjan 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 owx aj)6.t wuo;r why not.

In a lecture demonstration, a 3.0-m-long verticap+ai .w0(qm0zit ,nvzl string with ten bolts tied to it at equal inter(m0ii. 0nqv zp+w,azt vals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at.sm)0 *xciphb8t5hla c my6d4 constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops alop86c4c5xi b.mm0dyht )*hasl ng the way, a dish resting on a table?

An object that is thrown vertic+1l 80quc6 ps;dnabsh9jj cvc16 bl)s ally upward will return to its original position with the same speed as it had initially if air resis6lc91q6jscs1lsnu 8p;0jd v b achb+)tance 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 accelea1f *fa9ykel atk: c::1lcta4ration at the same time? Give exampa1ac kyaet:ckffal:tl941* :les.

Can an object have zero ah:k39y2fe kcfbxd.(d5q;u-s6wf fto cceleration and nonzero velocity at the same time? Givef (ky;6d3wtqo52fkebhf .s: u -x9c fd examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: .ab 5xnfm 9t:mFirst try to d.:axnbmt9f 5muplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the objec p 5c,jcw-ui. s)(kriw aj/f/pt graphed in Fig. 2–29.

  What must be your cat :bcb4gh(g8xr’s average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How la 0u.od hkw*-m7pm*jyb4 .b.hv, ssepong does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the sidewrgz34mi/asp2m , yhul0hi02 for 2.0 s, how far do you travel during this in0i 4yim2hu/3 a0wrp zlm2shg,attentive period?    m

  Convert 35 mi/h to n9vup 3c kfra;+ iw e1jr*e0m*
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from(f bs5i3.msou 3crl h9 $x_1$ = 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 steadi vs;8 eoel nw+okl o0zt7,v):sly at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 miv7:l0 v,oow os+) et;8zeksnl nutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five second 1blkfpk *.i0. lf4 )dvt2qby5w hen.rs between a lightning flash and the following thunder gives the distance to t5n0b42.kq ivklfbpy wf. r*t)l1 eh d.he flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a totai,fwlwyr9 ie* , ywo hf/3pb14l time of 4wy*,9 yeh opwbi/fwl3r1,i f 12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m away in 1 )0t 8ta;tiejr4.0 s. It then turns abruptly 8)rijtet0t; a 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 : h))b 3vdtjei0pb9n7tpo tw4pm -y0son parallel tracks. Each has a speed of 95 km/h wit0dvpjbm)wintey-b t p:p9 73s )t0h o4h respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behinzj6(; ire kn9znmi (2td a truck traveling How long will it take the car to reac kj izr (2n;in(em9zt6h the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters 0/p fwf tw9gij)up-y0 a tailwind that boosts itstff 9/-jwgwyupp) 00i 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 velocity of a complyvad*oyjrr /2h(vcv uu9;s*7 v(6a nlete round-trip in which the outgoing 250 km is covered at 95 km/h followv j ;ycav9u v*((l/6ovad7y* rhusn2r ed 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 l,un+p(dc (pouu b/.gep7k2 kat the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the g7pn/.k p + pk2,oudlbu u(c(eball 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 k)8n7 ltch c*ud)- bix5wqrx:9 grtd9sm/h in 6.2 s. What is its average acceletgr8 9-)xr5h b9ct d:ixw )csdu* lqn7ration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. Whk/ xjw7a4-qv*x5* js mc u6wjuat is her acceleration 6-mw x/qj4c7 ju5jk*xswv* au
(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 ,gh+bfnc:8 hye/usm 4 an acceleration of aboutf bgehs u8:hm+4 ny,/c $1.6 m/s^2$ 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 speecrmpvf( z0zqr,w l 023d travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, whpql 30,fr(zcv 0mrz w2at 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 to7ol)zt*1vzs2r 1h ltko2g3 8jf)o ai = 0 and moves in a straight line, is given as a function of time in the 2o*1l zt8zlotkso 2h)f3 )1ir7 avgo jfollowing 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/cznz 2qe+lj)dvgqji8 1+ r l9 to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume consta/zllqgzn cv)i9+jr 28q +e d1jnt acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. Whatd9bu9aa;2 :1b r)uxkznv:x tw was its acceleration, assumed consun1u k:z9b9t ;xbdav2 xwr:a) tant?    $m/s^2$

  A light plane must reach a speedi ..* 8v;liz.1l 8auwzr 9c,qmg,ccehhin vt9 of 33 m/s for takeoff. How long a runway is needed if the (cm.*,eg .ihv.cr98qlicvz zan 8l;1huwc,9i tonstant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprintee cf-9gptl zl33i,t;2-n lk ukr can 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 does9,-fce;i 23 llk3npg- tklztu 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 6.00 s7wlhnglt**+o . How far did it travel in that l*goh* w+lnt7 time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assuming xnpd dr3ln*h h)kz6z+v+o6c /a deceleratih +z ckolhvrp /z)d+66dnxn3*on 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 the ca v 00vrt hwii:69t*kecr compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collic6it*vei : hvt krw900si 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 wi 4drcvm :cf0*qth an initial speed of 95 km/h and human reaction timem4c*v drfc0:q 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 the stopping di : ,rfipz9e,3q1qjfi gstance 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 fy c7)7c l/tzzdriver looks for an opportunity to pass, guessing that his car can accelezlyt/ f7cz7) crate 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 10,0nvvvx+9o /6 :,p vryobpw(p0q00-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must t :6yvbw9x( v,/p roq +vn0opvphen accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45b1x)i/(ucrontlzm su*u-d f;o7o f34 km/h approaches an intersection just as the traffic light turns;cu4ido/b3tosouu7 fr-1 nx( )z*lmf 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 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. Ity :/hd 1md7epe hits the ground below after 3.25 s. How high is the cliff?e1/py:m d7edh    m

  If a car rolls gently p*omq7ff6a8oe l vbm7 uzhqon;,)*(j ($v_0\,=\,0$) 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 uyszo5dm v ;i74p 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/19c luyphy-4eg bif/: y5bob after throwing it vertically upward. With what speed did he throw it, and what height did it egyu/hi4bpyby c9/1: 5 ob -lfreach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. t65w zjyy ukq:7fxir,h* -h:cDraw graphs of (a) 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.jy5ru :k7: *-,chz qwhtxiy f6

A helicopter is ascending vertically with a speed of 5.20 m/s. At a hei/d j.a)zfa)h,qp*l ao0m8 yh 6vnffw*l 5wj5 xght of 125 m above the Earth, afypndz h,5a*xjm.) 8 6a /wq0 ojfa)h5fvll*w package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from restxc 2)9(x hrom: qp5z;wisf7 bn, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). Thii(x;q wm )pz7 hfs25x roc:9bns was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraicalta7b olgh ;pm9)l2:ms, cco7 tly) that a ball thrown vertically upward )tam9o, clh;g7l :t bo m72cspwith a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically us.p d6v99iocy i0;h3 dl:fn mppward 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 each photoflash of thvas +(x (2uzfpe apple in Fig. 2–18 (or number of photoflashes per second). Avsx(ua2f( zp+ ssume 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 past a window 2.2 m tall (Fig. 2–34heqa)b 3 bsy28 bfc2e2). From what height above the top of the window shae42b)e fqc3bb28 y did the stone fall?    m

  A rock is dropped from a sea cliff, 6aszn (zb7/ waahn7 q7and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how higz/bnz7nqas ( a7wh7 6ah is the cliff? H =    m

  Suppose you adjust your garden (pgju,lu7 waljqm2b ,v(l6 2n hose nozzle for a hard stream of water. You point the nozzle verti7j,q2l nw(pbu(a v,u2gml6 lj cally 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 the nozzle?    m/s

  A stone is thrown vertically upward with a speed oug+vd.goy;9n dr:/ 0wdxs s w8f 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–3dw yosgrs 0;uvw:+8dg.x9n /d4).
(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 m6 nmb iuh69km pney/1- .n rtinp6-4oupward by a window 28 m above the street with a vertical speed of 13 m/s If the bkmtm69pnhre1 6/no6n.umi4 p--nb iy all 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 velocit:g, 5-jsgbvgyrwq10u/y c .lay of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what-cly :g j/ygb guvw,.q05ras 1 periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tuno7y :cnc9b6, v7a5c wyptq8ob nel as a function of time is plotted in F t5o qw:6 vcy7obpny9c8a c7b,ig. 2–28. 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 accelerategr*dfz 6 bj2rcyj:c:- approximately as shown in the velocity–time graph of Fig.z2:: j rgrbjd*ycfc- 6 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 acceleration of the car in the previous Probl)w,6 h:i9vm,gjlcr;4 wmxyb r em (Fig. 2–35) when it is in ;ry 4m,:xlmb w,)cv 6rhg9wji
(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 tr2uw5h cv, 3 bse.ewv3qaveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph fodwovz 55uqa-.ckg4ly6g*:j f3 erg 0dr the object whose displacement as a function of time is gief:qrl5g *6 30-gudcavz w 45od gkjy.ven by Fig. 2–28.

Figure 2–36 is a position versus time graph fowmwe/.1fw )w( vnaw(ur 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 uvwwm(.fa1w ne)w/w( acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’s f 8g/g(hj2ssl(x zg3rsafety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2zj 3g2sf(xg8rhgs l/(–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 duebtztm:59i in3 to gravity on the Moon is about one-sixth what it is on Eart9tb5 m izint3:h. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained x x u y1q92zcf0cmz:,uby an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed aq,uzmc u cx1:2z fx90ybout 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 brizb7 u v4:7;hftwmk* cbdge, 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 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;*7z tfu7wb:khm c 4vb is it?    poles

  Suppose a car manufacturer tested its cars f nriwh y+ 1+; asulb5dp.c-tt8or front-end collisions by hauling them up on a crane and dropping ; -ny. 8ltts+ +r5dacpiwbu1h 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 tranmr6 h6cy.ce*:cn6+ d onxhg9cc2j/uvels 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 the train acp soz6;;:)bdn+fib has a speed of 25 m/s when it passe ifp6osnc+bz: )ab ;d;s 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 as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above theur3r6ml nb1 7ok 0v(xv m(mkz5 water’s surface into a deep pool. The person’s downward motion stopsr1rk km6(l ov unzx370m (m5bv 2.0 m below the 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 transit system, it is necesc/ c da z1+x(/p,:8h k3zzx6kyikwzmksary to balance the average speed of a train against the distance between stod , 6/h 8wk cxkxzic3zk yzzk+a:(p/m1ps. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and f7 by wi(*a.slwnop8 0)-rydnbree fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once commnbi.s n8 (o7*ydwp -0l yw)rbaitted. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a balaj b 0guij(4p)l is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green tu() b4j0 aijgphe 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 at8macls4e 8i e, a constant speed of 6.0 m/s Just as an e 8e ,lca4emsi8mpty 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 bjqnd tll0-zhqxx32 -ge77kz ,uilding. A second stone is dropped 1.50 s later. How far apart are the stones wl 0qxn7dzz 7-x e3gh-kt 2,ljqhen the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h ove.d* vm2yv*+a* mfb go jf;ikn5zz8wf)r the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed muz+* im.*o af*2bg 5vm 8kfd) j;vznwyfst be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crestsv:symnxx /vd x p1c8p sa*aj5gts):2, a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed i: jpystv:n vx1s,g2cd s8x m*p5 x/a)as 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 canqgj/ iyvd5sz0 4 ru0r2 bounce up one-and-a-half times higher than the second child. The initial speed up of the seco ry 5 02r/4viuzs0qgjdnd 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 1.10uqua;+dlk8k ;i qf/g/ -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 in this time? See Fig. 2–40. What are the results if the car and train are takdf;8/qkliuu;q/ +graveling 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 basebwpse v75i+ he*f0,uvsall with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, fromphw0*e7ev,v u ss+ fi5 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 acceleratibz; roz)s1c)v4ay wp.on 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 pa:3weg4 6hezlwttern shown in Fig. 2–42. Each intersection has a traffic signal, and wh63e4wg :ez lthe speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120 km/h pn( pu 9jev;a;-t1 l0+cexz 1xlhkw9 utakes off in hot pursuit. The polualwhc+vp(0xn;etu;p1 x-9e1 9 kzl jice 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 tha9ab4sy/rp7 yd w;a)x rp1 ;yvyt, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the sry / )vaywbyd a7941r;py sxp;ame 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 time. The fvv) l5u3 hws p*v.yw0girst 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 thep.wv)u05vylw h*sv3g 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 parazucd+fo(s4s 3 chutist to fall from a plane at 3200 m to an 34sc +d(uz fosaltitude 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 uses a co8* r;cvqg*1l:uxpyw 1fts m 9eu 3:csynveyor belt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how me*9u y;v*11p:y: u8x sltsq fcgrc3wfast 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 w75+ x rreu9r x0nsgb;a speed 1.5 times faster than Joe can. How many times higher will Bill’s ballrw5;0rgbx s7+ur ex9 n go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your /.,yln1 v ,b7nnw.pudno i spi3o66khfriend stands on the ground below you. You drop a ball fromnn.pnp6,17ln o yis3o hvi 6/d,w ub.k rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to fiiv/rkl:gg orgxq850ce 8 tn:5nd the 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 botg5k:/c eg 05x8rrnlig:8 qvuilding and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph fom7r9e2jdqu ac vgf( 0 m4e1dp/r 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 in9vf17gc p/mqa(u02 m 4dedre jstantaneous velocity? (e) Which bicycle has the higher average velocity?