Does a car speedometero-by xazp42 l7 measure speed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, give exai(ifx 8,k lz*z72 f(s- ur87uwknpnwf mplulwfz-*zxnw s(8k f(pr872,kui 7 inf es.

When an object moves with. o(ds-2ftndl t6nb vb1t idi fw):,*m constant velocity, does its average velocity during any time interval differ from its instantaneous velocity at ann*vw,bmffnt d21i d6s):(l- .tbodity instant?

In drag racing, is it possible for the car with the . h-me4c2jskvgreatest speed crossing the finish line to ljck.s4hv 2e -mose the race? Explain.

If one object has a 4ie3 3bzw3q n(9;dqgrb2ind9q.1v5 t u kdyqpgreater speed than a second object, does the first necessarily have a 2pu 1b3igy3d q(9 nvqndbt 3r5q9q.;zwked i4greater acceleration? Explain, using examples.

Compare the acceleration of a m cjkf01.zh :;bg m.samotorcycle that accelerates from 80km/h to 90km/h with the azabmmsh1. :c 0kgj.f ;cceleration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward a:o7k:mc5-qq fh wmls 6nn0bh7cceleration? Explain.

Can the velocity of an object be negative when its acceleragfuwj9viu zv,-ee, fm:3y*: ition is positive? What about vic- :weeyu9f v uvi, ,:fz3jg*mie versa?

Give an example where bgec5nw d:is6( ji:3jhspo87 joth the velocity and acceleration are negative.

Two cars emerge side by swruavqvz077w 5:4gaeide from a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car iv47qwe7 vgwz ra:5au 0s passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration deb rq3 1asskg)fck; t7 (if.)ud srvr 2p2+if+fcreases? If so, give an example. If not, ) i(r.3sstfk)vi2 urs7p21+f+dfrkq; acbf gexplain.

A baseball player hits a foul ball straight up a1(pc .n(enmf into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast acm.e(n1n fp (will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what + ffyg; n(vjy.is happening to its acceleration due to gravity — does it increase, decrease(.+y;jgfy f vn, or stay the same?

How would you estimaqw09 8 jbuk7vgte the maximum height you could throw a ball vertically upward? How would you estimate the maximum speed you could giwu8j90q k bv7gve it?

You travel from point A to pointjs1l y3lagt)biq5*j jso )08 z B in a car moving at a constant speed of Then you travel the same distance from poit08gis a3q) jb1 s lylz*j)j5ont B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string witqp4 sre q6z2,r)*lduz h ten bolts tied to it at equal intervals is dropped from the ceiling of thee2lz)qu zp,4qr*r s d6 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 nx0j ;ko 0- e;:uhcx:xzgol2 o mxy*an9ot at constant acceleration: a rock falling from a cliff, an elevator moving from the secondoh9ko; 2nx x-ye::c x;azg uj* l0mx0o floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its ori* k: 9amlj(nu r(mo 3q:9tfbrcfjqa/+ginal position with the same speed as it afna+r9m9(3*j b/lor(c jkt m :f:q uqhad 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 acceleration at the same;fas; l p2d)3 fpmyxp2 time? Give exalppp xm;fd3;2sya)2f mples.

Can an object have zero acceleratio/ m i(if*pa7xube8c31(knqi kn and nonzero velocity at the same time? Give exampb m(ixic n1aukk/*qe37i f(p8 les.

Describe in words the moti4govx s7u cl:7+wfdu 6on plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try touv 6lx+f ocwd7s74 gu: duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fiy eai0rlds0v*bseybfumn.1/: 2)6 b5pi;e xcg. 2–29.

  What must be your car’s average s: qjyx4(k+l gi s,gaesb+,,yqfo/ 3ld peed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h r pko4gmv/q3( How long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to thks6b opsu;hy98b- 2idhvoe )2 e side for 2.0 s, how dvboph 2s-u2)b8;9k so6heiy far do you travel during this inattentive period?    m

  Convert 35 mi/h to c vp2- 7ae hgq8;(7zc;8reoimxl:f si
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fro9oy)ze 2w1 s/p n0larrm $x_1$ = 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 95o(a+7ols /f7jis a- qce20jtp km/h for 130 km. It then begins t0(tp qs/a-7jas2olc ofje+i7o rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every )iq,zl7*s o/mg 8zyfzk+a hrtyux:00five 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 essential0zxuz yyhm8 rfzk+sqli*tg /a7:,o )0ly no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete l(f-nh;5 qqbnoxm6x2n0 j jebyz48 w*laps around a quarter-mile track in a total time of 12.nez -nbf(ohy4qj;8 *x5wb 6x 0qjn2lm5 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, movingc-s) y c/x7xo54orfx) r grf7f 116 m away in 14.0 s. It then turns abruptly and gallops halfway back incgx xs)o/r oxy f7cf47-5)rfr 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each has a speedy: ;j/can1ap kqa7*5m/ tgx - ppsx(ph 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 each ot*pg:m h7 jx -;pt1a/x sq5anca pyp/k(her? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling 3py 1;yvjx(seHow long will it take the car to reach th1yesx( p;3 yvje truck?    s

  An airplane travels 3100 km at a speed of 790 km/* nz7fkbry z8;jq9h)lh , and then encounters a tailwindy)l z fz*7k;98hrbnjq that boosts its speed to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete rounodhl-e *ba2xh 3k m;x5d-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the rkebadh; * lx-ox325mh eturn 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the+2zdljk;n 8co pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is;k o+2zjlnd8c 340 m/s.    m/s

  A sports car accelerates from re bsj8(/jsi: pz; ei2nvst to 95 km/h in 6.2 s. What is its average accelerat/s ibjs zn28pe :ijv;(ion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her wg:gnn3b;hr k wyi 40l-z +v6oacceleration y wbh-zv04kl :w gr+;3nn gi6o
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a partibn es lk1 ld5its*k0),66v rfncular automobile is capable of an acceleration of about fs 5ek,d)s 6n60iv bn1l*lk tr$1.6 m/s^2$ 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 then5;2hwdnbjb1mf 15 gjs brakes and comes to a stop in 4.0 s, what is its accelers 25bmdjn;51f 1bwhg jation 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 5 a)ujg7y47uotg4e f lcar, which starts 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 47foaeg4yt5ul) u 7jg velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What wmh wogq-as:2gwh 9 8446pyzz.xpyd6 sas its acceleration? How far did it travel in th zyxs6.w8hywpapg9s4zmo6:4g 2dhq -is time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. Wham9a;cyq..jgsba 2t 9 ot was its acceleratiog. .2sm9tabao c;j qy9n, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a ;xnvb)tap.v8 runway is need.x )v 8bvpnta;ed if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blockhrjab9mb)1dh* drx 84s to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average abjhm4h8 b9 x*r1 ddr)acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest in 6.00 s 0rp3h7hii+ifvwm6-aj: axf1/ gatc +. How far did it6caga0 m ixhf1 hv/+fairi+p- wj:t7 3 travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 vrn9372 0ptv7uyeefgm long on the highway. Assuming a decelerat7vgnye3u t7p 29vref0ion 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 alvp .d8 /pfcwkb*g,-tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m.,*w /-pkcafglvdp.8b What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car wit/rl-d( v/ iqi9rda2 m 4wtz8lhh an initial speed of 95 km/h and human reaction time of 1.0 svd dtir8/z-/m 4a hqr92 ilw(l, 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 stoppindd2agq)c4c ) pg 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 dr 0k 23mftn, kb:i+iol( zv /uh;n:bfsaiver looks for an opportunity to pass, guessing tha/ kku:tb2 a hn0,nmo ;( lsifbvf+:3zit 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 e s7c59fg*xqw hudu*acb13e5 than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runn9 d7 fgws** u5beacexq c315uher 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 awj eb 1q/;6mj/7hcesv yu86jcs the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m asy; j/1 6eecqum7j/ jv6c w8hbway 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. It hitszse5ibx.:9n91-) l ltfnlwaw the ground below after 3.25 s. How high is the : w l1x9iet9n .w sa-b5ln)fzlcliff?    m

  If a car rolls gently l4lqz biqxj9vemv/g+u534p 5($v_0\,=\,0$) 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 soqq56j+2p7/5tfwcn;q1 f ,ktfhi tv with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vertically upwardee s0c)h g0ln8raw+ d(. With what speed did he thsd nrela8gc(h0w e+)0row it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under tpq*:j+u qac6 yhe influence of gravity. Draw 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 aipa6+cu:y*qjq r resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a hekezc to4ik :m l.:**iwight of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: mlc:w*iz *i 4o:e.kktThe package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show thatf; (h: ht+ ; gtgwo8l j-jy q0tvfcbks)-e()tm the distance traveled during each successive second increastg0tf ; +8 y tjs-jh:(elq)hw(-gfkcvb o;)mtes in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown;pbho 3 -kcji 2hwn q5zv*e3j;ues 6x: vertically up*2:z-kwbqo; vn eh6sp5jiuc jxe;h3 3ward with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18.0 zm442kvhp1t0a e r7xxm/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 i3 3z zf8s( udni*:y sn)7makemn Fig. 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 unclear k 3 m*)nsas z7(8:ydz3neiumfones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a wi4vljbgdf+1e 7 kaf jv;;s: y3 q*rr.uqndow 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone fall?u4 ygdjv7 rq*ff. k+bal;s e13rjv:;q    m

  A rock is dropped from a sea cliff, and the sound of it striking thel-ull)bg)kn.qd (* t n ocean is heard 3.2 s later. If the s.)u k)g- ql*l btln(ndpeed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust yo qq83fplken/ )t*qd .dur garden hose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When yo qkdqnd 3) *tefl/8.pqu 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 of 12.0 m/s f9n / n5; ntiikd*n3cuq0 odci1rom the edge of a cliff 70.0 m h1i 5qon *t;di/nu kncinc0d93 igh (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 j8fhn eudr(iq) qqz+ k,l;v23pass upward by a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the str +n2qhu,zq)(3 fvkjqrde;i8leet,
(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)xl p )5tp4-qd+oixvm velocity 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)x mlt-oq pdx vpi45+)) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel e; l c/y4b ,dwmi(p/6mvm /zdwas a function of time is plotted in Fig. 2– / m mdw4clp//;bdwe6(vmi,z y28. 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 auto4/x/h*pz ce5 kqrg: bimobile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short f /ebc5 z4xr *khp:igq/lat 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 Problem (Fig. 2–35)jl4a i3q*z ynwy 0x98v when it is 3ix q y*v0jz8y 9lwan4in
(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 traveled durinjy xc;8 .3iyh qf3fd4mneb;g.g
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t gr 4 +y: ,qu nzkh;k,qj-lw:cvq uvw6u(daph for the object whose displacement as a function of time is given by Fiyqkckw+- 6(q :v;, z,hv uwunquj4l :dg. 2–28.

Figure 2–36 is a position versus time graph for the motion of anwj .r)pd nozquzd- 2,* object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the posidz)j -* dp.r n2quzow,tive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above 7 : ;usorn* os;80.fetcoexzea firefighter’s safety neto ; s.8 :*tozoru7x0en sc;efe. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on s* / u8pa/lxxhthe Moon is about one-sixth what it is on Earth. If an object is thrown /l /ah8x*usxp vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder idcp5t 08rp0w8z k6kn seat belt has a good chance of surviving a car collision if tp500r8z k8 nid w6cpkthe 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 roaw*f,/f qy3/ofk,9 b lnqfhgh2d 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 th fff*ok,blq 3h/n9q,f/y2gw he 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.udz lm4j/ r5bcp:r2)(otk c z41hjyf front-end collisions by hauling them up on a crane and dropping them from c ):t(or/2 fdby.lu p 4cjhrkmj15zz4a 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 trav ecx.bmxv(:+ mels 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 un5s9kaoclle) mezoe5 r7 q.4c:iform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who i 5:e c7)ea.lkrcsz9oo eqlm54s 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 divin :a3fsn- 4 hc jb02kjyf/t:ghsg board 4.0 m above the water’s surface into a deep pool. The p3sh/t:cbn 0ks yfg4ahjjf:2 -erson’s downward motion stops 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 necessary to balamp0y a2*a; nb*sl,ylk nce the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two syp* , l;san*kl bya0m2ituations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fish. Su )1 al/vc)*aes; qyciuppose 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 ev;a*ca1)/cysi ) luq to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so z .7) -h1mqy/ck:97fszjgz.bsia ptk jtl( n)that the ball will stop within some small distance of the cup, say, 1.0 m :c1az9 fknziytk7- z s/jgp)j..)b t7hq(sml 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 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 a88()rn .6rr+eq c a8lgi jbumo constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts fromrig+ejmcr(buro.8 6a88lnq) rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A second stone is dropped 1**zcrwhe:v +3y.r(ycn w0yrl.50 s latey y hr0 wrz3yrw.*c+v*l :nc(er. How far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the m)lge ce k(6xvh)9k:fcourse of a time trial lasting ten lexfkk)h: l)v 9e6(cg maps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at 18 kp21hm+gda /j aby sjzid +s2:7m/h . At the bot j/b h s1:ama+2dsi2jy+zdpg7tom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first x1crhn(xl4g,ab ,cn+ child can bounce up one-and-a,c1+4x a,(gnbxrhn cl -half times higher 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 overtakes a 1.10-km-m uo -x xo 5*o;8+mvy/wupkqg2long train traveling in the same direction on a trackg 2;+/- ky58vu ux q*oxmoomwp 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 traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In throwing the bajhk,o(q.ug p3:zd4g dji5 wb.seball, the pitcher accelerates the 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 3pi dk.qb5(: ,uhzdw4. j jgogduring the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acsl*-ku paf*n/ celeration 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. 2–4 la 0yw;lr1q sb/tjm7 *ve-1bffd,. by2. 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 int b jysma1.l07 yfv*w b/r,le;1t dbf-qersection, 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 spa6,jw 8wpe:u 1jo-l-9eled tteeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant accelerati6jwp do u8t1 teje l:--wael,9on.
(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 second)(wj. 9f.oa5ub pgj agj/nfd- stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at tha (go-9u)d. 5pafjf n.b/jgjwe 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 time. The first stone is5y.u smgj+: xs thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4..j y+s ms5:xug5 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 woulf i+ev 5+22zmg 0veajh4v n0sed it take a free-falling parachutist to fall from a plane at 3200 m to an altitudefz20vee2e +mjn+ vv4h0 gas5 i 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 cony0 dm6b cz6ok/veyor 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 cookdom 0by/ck 66z, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe can. How mt+ o)67 kd :zd4a+ zuukg0fyqlanq:kd + gak 0ydou)zt+6f4u 7lzy times higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cla;6kd( eqmz .hiff while your friend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend thadzkh6e.; (qm en 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 pa4cr6gk mzcuf)sm/ -l.6aj ef -rticular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much differef cs- az/rumg- k).j 4l6cfme6nce does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for tgh i ;j932pud zgwd, :iwcq6 wsn*j0f/wo 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)g zwhi*w2q,fpgjn wdd9c u:/j;i63s0 Which bicycle has the higher average velocity?