Does a car speedometer measu09rhjs.lm6gkbxfrk ; epv0 c1s1 n.-wre speed, velocity, or both?

Can an object have a varying speed if its velocity is cons dh20 bkr7dcp7tant? If yes, give examples.dd hc207kbr7 p

When an object moves with constant velocity, does its average fd34sw6pv,am)3 azcog7 , mnwvelocity during any time interval differ from its instantaneous velocity at any z ,34g acapw ds mw367)mfvon,instant?

In drag racing, is it possible for the car with the greatest speewk,ajrpp6o/ux i97rnwk3f*p 8sn7 ;w d crossing the finish liw8 ipjx6r9no7,pu/ 7fps kr a*3nww;kne to lose the race? Explain.

If one object has a greater speed than a second object, does the first necessarirteux67wsg r:e +*ugehf2 7 t5ly have a greur72e76* :5 g eftgx ue+srthwater acceleration? Explain, using examples.

Compare the accelerati l 9xrxg1t9y 0z zvz64klg0yh0on of a motorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicykzrx0 4l0019 g vzhgxlz6y t9ycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a uxb.ntn6. o/dx ri3z:b0adx 1southward acceleration? Explain.

Can the velocity of an obje lhjv xi3-n;.fct be negative when its acceleration is positive? What about v;n 3lf. vhjix-ice versa?

Give an example where both the velocity and acceleration ar:xj o)eil eeu an7b a y12w0qi012vpz(e negative.

Two cars emerge side by side from a tunnel. Car A is travelingxkqz(/7bw9. 1aub zsei4q 2uc 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 is passing the other as they comebcaxzu4( wsq .e z219qibk u7/ out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleratf2 ds/bc)l0 yib-mq65o t3bz nion decreases? If so, give an example. If not, explaid bm2y s53/lb)nqc0-tz6obfi n.

A baseball player hits a foul ball straight up into the air. It leaveszvz/gjz*)m )ab wk:0h the bat with a speej) 0 hgmvwb*zzk a/z:)d of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object 3;f.u*gm+)zxdwb ftwzl4. gnspeeds up, what is happening to its acceleration due to gravity — does it increase, decrease, z.b lz;x4u.fd*f)mw w t3ngg +or stay the same?

How would you estimate the g ,; 7hpd,qhelmaximum height you could throw a ball vertically upward? How wh;dgeq, 7pl h,ould you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at pz,nm )gmnl*;kf) (bta constant 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 ff(),nm )p*zg n; mlktbrom A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts f21d hxf ahjxc,79fltz ,u *q-jdd(k 8tied to it at equa (jat9u7* c dhlj,fd1fd8f,xx-2qkzhl intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. 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 constant acceleratie w:803 v nhyigue(k0/uo8qqdon: a rock falling from a cliff, an elevator moving from the second floor to tni8hkdy (0 q :we3ue/vo8ug0qhe fifth floor making stops along the way, a dish resting on a table?

An object that is thrown verticallymg8o g9c4 7qov upward will return to its original position with the same speed as it mg7gv oc98oq4 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 mhjjw9af0 :5m* lr +buand nonzero acceleration at the same time? Give exa+*mw :ja05mb9f u hrjlmples.

Can an object have zero accex/ 6k;xjwitvb1ja0 c )leration and nonzero velocity at the same time? Give exx ;v 6ij)a/xjbt10w kcamples.

Describe in words the mot0fmh,h,e8bny32n iui ion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the 3bi 2h0imnny8,,hfu emotion plotted by walking or moving your hand.]

Describe in words the motion of the objeco 2l d.njhbp6mud )q6x87tve6cag 3s(t graphed in Fig. 2–29.

  What must be your car’sxoisw 0s 16zu,).cyxk average 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 fly 15 km? sv vcu( bq:6j-   h

  If you are driving along a straight road and yo 0uj1o.1sjwtg0p+xhe u look to the side for 2.0 s, how far do you travel d1hj jwtg +ousp00 1e.xuring this inattentive period?    m

  Convert 35 mi/h to *mkfb8 n, jf*urx**qu
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from ce*wx4.mm26 csy b mj.$x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home from school steadily at 95 kmm tkv j),xmhaq2p/68nt 8.qkd/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after dr, 2 m xnt/aqtkh68.jvq pm8)kdiving 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 five seconds poerp25i 6c5 kbetween a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound 5ckpepri 2o65in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a qcmp,o088pgah y x 3/emi 2*sctotal time of 12.5 2 aqxg0c*8 p, ih8/ms3opecymmin. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in +p+e6h, xg)gocwqo*h a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallopsh +e,whc+og oxq gp6)* halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on param3(xo7bz iim, ok -s-dllel tracks. Each has a speed of 95 km/h with respkoi--zm s b (,dm7x3ioect 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 behind a truck travebf3,xx+ rx9d:q1yw p3imau* aling How long will it take the car to reach the truck? fb yw1p:*a3ix9 mr3xa+qx ,du    s

  An airplane travels 3100 km at a speed of 790 km/h , anpl8p uy-t3w :ad then encounters a tailwind that boosts its speed to 990 km/h fyt wup:pl8a3 -or 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 4y2wlmmy+/2 8q;ybe/ 11q f*z ecx+gazakvkrof a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-ho;1yqwy*/m+ mevkcqg+ey1 kl8af bxrz24 a2 z/ur lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant spu1pl0qbhrb2t 4/7i hoeed hits the 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 speehr 4hb7i 1pu0 /t2loqbd of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its average 4ppvl - g4*tw0hp7z r2keu+fdacceleratd 4gp2 -lp*4vwzkt0u r+p7efh ion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates frife umw-lk w)(- tb4m7om rest to 10.0 m/s in 1.35 s. What is her accelerationt 7u) mlebwim(4k- w-f
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular autos czcl4+1gvq: mobile is capable of an acceleration of about 1z lscc+:4gvq$1.6 m/s^2$ 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 tkvi7evt hj3f0o7r e 5l 7.x6gonj0z7 khen brakes and comes to a stop in 4.0 s, what is ij5 ge 0.77kin zv3xl hfore60j7kt ov7ts 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 t = 0 and moves zwai 7p a,2kkj j:y-bpi840gqin a straight line, is 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 zypqikai2,g jw7b4k8:-0p ajand on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was 1vj exeudn+.1 uu6a;qits acceleration? How far did it travel in t1eeu 6.v;+qaduxn1 juhis time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was itm7.lvo 4j ammv )gk3m4qes)h7s acceleration, assumed constag mshmq )lv vm)4a7m4e7k3.ojnt?    $m/s^2$

  A light plane must reach a speed of 33 m/s o.5r;-usj i cpk9dd+ p u:hct1for takeoff. How long a runway is needed i+p ph rcuj.isc-1k9 dodt:;5u f the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially t pwwu( )c8ikq;yr)q o7op speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this swoc(;8iyqr)q wu p)k7 printer, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformll -htxwo0 nnd)*9q mh5y from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that nnlowx-)0 h5dt 9q m*htime?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assumus84z4. -/jisnfrh pq ing a decen/ rs- i4uz.4j8 fshqpleration 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 fronu j5da4gd;w ue g+06mlt 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 collisi on? Express the answer +56;d glmu aj4wudg0ein 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 distancg4e-au1c/ q: y hi53.vnt9sde+kns,o 4oqtuf es for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, for-eku.v4 sos q1,dyo5t9f/t +in n egq 4:auc3h 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 distance of a car4 t-p. pr24ipgc tu7mw 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 cb3:,nbgt w4n highway. The car’s driver looks for an opportunity to pass, guessing that his car c,b3 t bncng:w4an 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 compi oz 2h0ngv s2.wqwb1kzl/2o 9lete the 10,000-m run in less than 30.0 min. After exactly 27.0 min, the2oz/.n h1b0wg9qozi 2 kw2lvsre are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection j 74tk r*9udx os-g:vkpust as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the 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’d9o-s4uxk rpv g: *t7ks 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 to+ htc56zdbbty u9vz;7 k+k/mb p of a cliff. It hits the ground below after 3.25 s. How+tz b7tbvub y;5hdz6 m9ckk/+ high is the cliff?    m

  If a car rolls gently7 i*wi /xhizt78d l5ml ($v_0\,=\,0$) 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 8rh.npmh, n1kinto the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vertically x,drkj5 b*uy )f: w;s ong/n1iupward. With what speed did he throw it, and what heigin,y)d;51 xk j*rb og /ws:fnuht did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the zz.bf-j7 dt -vztsx29influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 tv tb zj72sd tf9z.-zx-o t = 5.00 s . Ignore air resistance.

A helicopter is ascending vert mnn 8bc1 qhrd3b;o5,zically 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 reach the ground? [Hint: The package8b1rzcd h mqbn,;5n3 o’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled during s j5(:zprxm* ieach succi zpxrjsm5* :(essive second increases 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 (algebra4 eo4b/*h;copf8o8mrl6 mi ai ically) that a ball thrown vertically upward with ao bi4*8a8/h;cof4r om6 lmpie 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 : mpzol93utz -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 phx sq-vgx:b( q v;6f*yy k76exootoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume y(q7- seqv yvx*:b6gk;f6xoxthe 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 v6qw6(h:bnv1wai vj05m-okp a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone falln v(k:a661pov qj mw5 w-vbi0h?    m

  A rock is dropped fr 7 jdiscq(q*aqvr*)7w om a sea cliff, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how h7*qvr qdiws( )7*cqja igh is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You pointpve6g + cn4;l8kfx8 gi 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 strikg6gn;+ ci kxlpf8 48veing 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/szl zjt*( xc;0k from the edge of a cliff 70.0 m high (Fig. 2–3 zczk(x0j;lt *4).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 2 pm ibit5;re:38 m above the street with a verticm;p3 t 5ber:iial speed of 13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a functio k4jx8*xoqq v v2iw*k)rm e03fn of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of kjfq x)e*k8q w4ov0i*xr 32v mthe acceleration greatest?

  The position of a rabbit along a straight tunnel as pdag1f-c j0i8v/k r:pa function of time is plotted in Fig. 2–28. What is its instap:vr- c0d8pkf agi/1j ntaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as shown inm e) * ouaz.wlx p254rjdl(.js nnv;q( the velocity–time graph of Fig. 2–35. (The short flat spots in the curvawole(dn(. jp5;) nv4sjl*x2.muqrz e 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 accelerah e-a*ko9t5 hution of the car in the previous Problem (Fig. 2–35) when *kh-otah ue9 5it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object travel oc ,btemjq(2*ed during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functi)zgtwc n .vka5wuo(0k 5fp, 4aon of time iao , 0 awckupv z(5g)5tk4w.nfs given by Fig. 2–28.

Figure 2–36 is a position versus tuaazmk)d( 4b)+ edbah q+ 420mwroxpu r;r7 y;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 time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowko)uu4we;+hbp;r04 xdz)ba+ma r(ma27dqrying 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 safkt i/ui9rxk,ub+6 bk- ety net. Theut-ir k6+ibb ,u x9k/k 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 the Moon is about one-sixth what it ixhv+ d6j/2d vq.a,t xks on Earth. If an object is thrown vertically upward on the Moon, how many timhxxvda6,2j. k/ tdvq+es higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is proper- /v d1-vnbfgi2,owfply constrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not e fovg/b-1nf2pd w-,ivxceed 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 bridgn-gg9,uo2c j le, 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 b2cg-lu,9o n jged 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 dl b3ku0f;fc3mz)x+ wnom+fmt6 x2, q8) km yufor front-end collisions by hauling them up on a crane and dropping them from3xfu80 dkqm)b;l3o mkct,2+u nm6)zmf+wy xf 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 travels ab vzl4m5ao6 ic yy*+ yaa+ex0s2out $10^9\,km$ 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 traiq shp hv(+dx-fk()j z7n has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the phd+xs hfv-( zq() k7jspeed 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 2.i *pzzj1jhiq4x r as,e r4*mprz7)ethe water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimatem zj4zipr zia**h,.xe47jp 1r2rq)s e 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 syst )h.2* t t*du1 +*iuhfvochvhcem, it is necessary to balance the average speed of a train against the distance between stops. T2h*od *)u ft+thvc1ch i.h*uvhe 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 free fall straight downotr1qyu ut8eo,30ut 3 when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it tuu3reotyt, 308t1quoakes 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 bx26d7 4g9kkotbc1xm3.y - )mttzqhuo all 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 dox1hxkd36t2- uom k9t.mq47g cztbyo)wnhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at a constant;nfp e*,m rri8 speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest anirr,nfm;p*e 8 d 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 hir99aj rlm0mot56f ds9gh building. A second stone is dropped 1.50 s later. How far apart are the stones when the s9m9sd jr orm06tl5a 9fecond one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a tim l) o.kzsx9mf.p sf -3m)hsb;je trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for t)khz)j.. xf;m mlb-39ssps ofhe last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he m ;o*u8sw6.vft jdo,su oves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his.wsj6uu ,8 ts*dfvoo; average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The fo2d.56nigz f5jq( u ojirst child can bounce up one-and-a-half times higher than the second child. The initial speed up of the second chio56qju(jn5 gfziod2. ld is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train travev ,ey- b2g4tssling 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. Whaev -42ssbytg,t 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 thr5ma0b+fzv z)v ows a baseball with a speed of 44 m/s In throwing the baseball, thev+0 fm b5z)avz 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 during the throwing motion.    $m/s^2$

  A rocket rises vertically, from restvn3w:vpbl 4r: , 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 intersectio-gqu.ka edx:2 xt;84uhcme0r n has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green 0x;a -8r dexuh2cqmkt.4u: e gfor 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 consx j-(,d,os9v mrzfyoq)e :pk3j .+fimtant 120 km/h takes off in hot pursuit. The poli-fik:(vfp.m)e+ rojq3xd o,9yj ,mszce officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that,7j.(n gkagq 0zw rja5f nk))0c a second stone is thrown straight down with an initial speed of 25.0 m/s and the taz.0ngjf )k75 0agqj n(cr )kwwo stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same timeyuk:ky. s /aql ,h *beqpew7/n10 tun:. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With whatqqlnsuen*kuy: ap/ y0 et:hw b/.k1 7, 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 paracl+pu9 mub2u(v+c: m0gn+wx lc hutist to fall from a plane at 3200 m to an al9+b(lg wuxmlu+mc 0 +v2npu:ctitude 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 cwngfco)76n 3f( drxz* onveyor 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 fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in bucrn6x(7f3f ong zwd*)rgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a sopih,s s q/w2,sy 6pb)peed 1.5 times faster than Joe can. How many times higher will Bill’s ball go tha,iys qpo b,sw)26/psh n Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend standsup kbriq,/c1: s9g .7mfah:be on the ground below you. You drop a bal1 hr g:/ .e,cqm fapb7:9usibkl from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it 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 q- t:km-6 qh9adtkbqq;cdc0 )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 building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. qkm);qtc:0 6 q9ckdbha- td-q How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for tw12;3 zp glemq0ac4a;md z/4kxl6a rj bo 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) Which bic0lp64 remdax ;3alc1;gzm z/2baqj4kycle has the higher average velocity?