Does a car speedometer measure sp68 g-c39vcgjwvp a +qeeed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If e0w- +g: a8g3hhucjdd yes, give examplejhdca 3 uggh:d 8+-0wes.

When an object moves with constant velocity, znkxv/: ,k6xh rq6uip. yg+i-dno 07c does its average velocity during any time interval differ fromoh0.gdz,qn/u6: +-i crnx 6xky ikp7v its instantaneous velocity at any instant?

In drag racing, is it possible for th.byp6q pblsa2 ,w0dmaw8/k63 lgd7 lhe car with the greatest speed crossing the finis,3 abd lkgl76s/pqbh0d2w.la p8my 6wh line to lose the race? Explain.

If one object has a greater speed than a second tw36w/mcp z4t:hkx3u object, does the first necessarily have a greater acceleration? Explainw pw6xk:/u mt433zht c, using examples.

Compare the acceleration of a m;vipiv:c +dczv33. hls e;oo: otorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that: oic;zp+oh:;c33vsld vvi.e accelerates from rest to 10km/h in the same time.

Can an object have a northwarde2f . 7jfuw(dg velocity and a southward acceleration? Explain.

Can the velocity of an object be negative *4*9n7 dmug u2sy0,rmrnuq yu when its acceleration is positive? What about vice versa?umq ymu*,rnsrdn0g yu79* 42u

Give an example where both the velocity and accelerati6pgty;lpm)cy you2j.t5l 8r9on are negative.

Two cars emerge side by side from a tunnvnq vi:u)7;gjwk ::h(o ( pgydel. Car A is traveling with a speed of 60km/h and haphw g( 7y):;:(ougdjqk:vnvi s an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increagl4 u4ern -4mcsing in speed as its acceleration decreases? If so, give an example. If not, explr -cge444u mnlain.

A baseball player hits a foul ball straighto32z-+zg.k 4 s8r*kdb29ngoceszcr z up into the air. It leaves the bat with a speed of 120kg24 28 zb3+zden*sczzskg oc.9 -k orrm/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happ6be 8c:ekf; 3 :jdctjjrg0 zx,ening to its acceleration due to gravity — does it increase, decrease, or stay the samj:cfrd 60:g 8ejk,jt3cx;bze e?

How would you estimate the maximum height you c; yahy0wxit)hr4m*e ,ould throw a ball vertically upward? How would h 4ma, *xe t;w0r)yhiyyou estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed of Tzr660fe ob7myabr2v 5hen you travel the same distance from point B to another point C, moving at a constant speed of 90km/h .5zbvm66 r ab e70f2oyr 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 with +pygq as.+ xc7ten bolts tied to it at equal iqca p+ +.7gxsyntervals 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 accelera2q :ir u/l b;w,bdq3iz3vr c60ubtj0e tion: a rock falling from a cliff, an elevator moving from the second floorbe;:rzlti0/ ibqr3cj 20buvq,u6 w3 d to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return tlbr ; rvwycp21-gtccv+e:+ 4p o its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, ;l+p1 wg:r2 by r-c+tpecvvc4how? [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 tim2 glu--+)bj 35hmpakkzfaf+ c e? Give e)fa +k+k z mc--lbjup52afh3g xamples.

Can an object have zero acceleration and nonzero v rhobj998ksf 405ca h.g*bdrb elocity at the same time? Give .bga0 rf9j5o kdbsh4 8*h9cb rexamples.

Describe in words the motion plotted in Fig. 2–28 it 2; zouvn)zf34t;hgb3uz3 i in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or m 3i3;u; tbizohz)vu f4gtzn32oving your hand.]

Describe in words the motion *c/fpqqz:tf t 8 1zc3bof the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25 h cmk42f*dk77ci rig7q ?    km/h

  A bird can fly 25 km/h How long does it taum 7ul fk;vxk-mrx3f,) 3 *vvake to fly 15 km?    h

  If you are driving along a straight road and you look to tn ,p,nih1bwv*2d5u9 s j yiy7foz90 zkhe side for 2.0 s, how far do you travel during this inattentive perizsvyj, 0u* p yibof9 dwz2n1hnk5,79iod?    m

  Convert 35 mi/h to jix :bt-nian :,wo4a ,
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fr qoed/9 1*qze:pwziz* om $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

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

  You are driving home from school steadily at 95 km/h fole0:y 9bv7t /kskikv. o *r(hhr 130 km. It then begins to rain and you slow to 65 km/h You arrive7ht:svlk h0i rev*yk .b( 9/ko 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 five seconds between a lightning flash a*k ,i.-9 kjf 8vosluvmofxe85nd the following thunder givekkm-fos8 , ve*xou iflv 9j58.s 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 in m/s from this rule.    m/s

  A person jogs eight complete laps ajl b4or-l cm+)round a quarter-mile track in a total time of 12.5 min. Cal4) ll+rco b-jmculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainev5hkxs1rte; 4 r in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calculatx4 k1t ;s5vhere
(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 othg1 x*)pk i6*fdiq yfh1er on parallel tracks. Each has a speed of 95 km/h with respect to the gdfpy *qi1i61h kxf )g*round. 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 traveling How long will it takxb4a fok9. ke,e the car to eo9.k,4 bkxa freach the truck?    s

  An airplane travels 3100 km at a vp*,vkz(qdxc7ub61o speed of 790 km/h , and then encounters a tailwind that boo, (vvxzb1*o6cqk pu d7sts 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 round-trip in whs8ke. pfw jkoxy)rk6z5e6,zu 4(f* ncich the outgoing 250 km is covered at 95 km/ yos e *xzkfun8k.j,erz pw5(66c4fk)h followed 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 spomz z()sm.js s+i0fdkp4 d35 m2xg 7pkeed 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.0dxdz4mf2kpgs5sj k m ( 7+z)3mo i.ps What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from r m,ojs8-)afc78aizuhy3y x,lest to 95 km/h in 6.2 s. What is its average acceleration in , c ,a8amh8sxfl ou3y-7z )jiy$m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s ss/en )lk*fkf e+r+0pin 1.35 s. What is her acceleration 0/ee)*rkfpl+ss k+n f
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particulz tll, - dg2m:rrqm:h2n 1yg6rar automobile is capable of an acceleration of about g ,:2t2r6mnh qdy-lrlm1 gz:r$1.6 m/s^2$ 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 1)s m42l6yy wie10 m in 5.0 s. If it then brakes and comes to a i)y2we4s yl6mstop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing sbj s/;z,* bx2suuga/car, which starts from rest at t = 0 and moves in a straight line, is bs s*x;/u a/z2,u bsjggiven as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6lzw go2)rlb)*.0 s. What was its acceleration? How far did it travel in this time? Assume co)rg bol)*2zlw nstant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its ac*aex*fdui5 (gceleraufx ia*(*ged 5tion, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway iz qqsa5qd2 /i 2pcde8*s needed if*5daiqde 2q2spq/ 8c z the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to esseaeu7u*az.yk :v05h,rw 7 bc+ hkgp2 zdqny 3e1ntially top speed (of about 11.5 m/s) in the first 15.0 m of the race. Wu w5da.z1uzkb2:7 a+ g k yc*hyv0,3 qehpner7hat is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to r : b162 yiatquz;rnf8mest in 6.00 s. How far did itt6 zuf a;:r2iqymnb18 travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Asph 5r i;-j,2 jj0rmqaksuming a decelerata q, jjmk0rjr5i2;- hpion 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 themi 51vuk ec-*+dha5dp 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 in terms of “g’s,” where 1.005 duidm*c-ap5 v1e kh+ g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping dista2 glg )y .e(5pjd3uhomykcql:b;aq36nces for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, f:kg; bq5yyeq)l 3o.j3 6 ul2camh(dp gor an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equatiow3af-1z4a3 b2r vxsknn for the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck g z0 vlyh)p7sb/nf,5f yoing 25 m/s on the highway. The car’s driver looks for an opportunf0)p/ nvy,fhzlbs5 y7ity to pass, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 min. Afterwmtjgb.3a26 lbq,g3i sud. i 6 exactly 27.0 min, there are s2gibjl i . ga.,t6qbd3uw3 m6still 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 intersectve5),f nnc7*zyvi, op3hhx5 tion just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, an z n,v p)cvxo*efi357hnyt, h5d 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 cli2)mmfxg 3k/r20rifve ff. It hits the ground below after 3.25 fr2rvm2emfgki) /0x3 s. How high is the cliff?    m

  If a car rolls gentlyeijy35/te bz6 ($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air with a speed ob;zkiz -ihsve p-a6:8f 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a6iq3/ (hmfxcew(ohpqxx)+ g/ ball 3.0 s after throwing it vertically upward. With what speed did hh fgox/hqx)(+xce 6mpiw (q3/ e throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and f n.p:e3at; flfalls under the influence of gravity. Draw graphs of (a)f;la 3.fp: tne its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a height of 1q5ttoy7n /eehzl u21325 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 pa7 51uoyeztel h/nq3 2tckage’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled dur4zv tgqmgucr3i8+c0 , jq1 7jsing each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown bygz8c q1, 73vji 4+gutscmqj0r Galileo. See Figs. 2–18 and 2–21.

If air resistance is ne91;wjy8egh29h b4x k;yuub a qglected, show (algebraically) that a ball thrown vertically upward with a seykq 9 84 u1u9b ;yhag2hj;wxbpeed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward wit9/uxr)goija 5pli,3r h 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 the xf65dt;, :chtzp no +papple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions,zt;h:tn6, pd+fx 5cop but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 04ic vtp-qsrx5nyl3dl-v 7 )g5.28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the s5cqv)rlyg5dn vitlx s7- p3 -4tone fall?    m

  A rock is dropped from a sea cliff, an o ol2*icgss(,d the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how his*2 glo,so ic(gh is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard strep5. gya7t rzfmm57zuq-4 t9ream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly mo 7 gr-utzmz5mr9t f4y q5.ae7pve 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 7c ;wq;brlef0upward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fil;bc;0fwe r7 qg. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a windo u-b *+zn;ns uqs.n6o8rrr;wv w 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the streetr.nv *n ;rrowq+su uzbs6n- ;8,
(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 tr)y sfeg )-gfk3ain 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 periods, ifk3-)e)g gs fyf any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a f5bz n1keh2w) k,low k8unction of time is plotted in Fig. 2–28. z ,kn15 )ww8k hbe2kloWhat 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 acceleratebi8udx/k-q 4 w approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve repb- qi8u/k4dxwresent 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 ac4lr:68g5xkjer 8+ l 6 hkhqvbjceleration of the car in the previous Problem (Fig. 2–35) wlhj+6gk6rlxh jb8e :q8rv5 k4 hen it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object travl1kcdd 9t57 lgeled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph 7sruev t*-h.nfor the object whose displacement as a function of time is given by Fig-th usv* 7r.en. 2–28.

Figure 2–36 is a position versus time graph for the motion of an obj9gjdpo c(r44sbd; pj:ect along the x axis. Consider the time interval from A to B. (a) Is the object mopr4d9gd jo :pbj4; sc(ving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story wi3cdjtply w 8( 55th:dtndow 15.0 m above a firefighter’s safety net. The survivorjwc:t 5htty( ld85d3p 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 is on Ea p0q hyn.frx.ej516purth. If an object is thrown vertically upward on the Moon, how many t.0fphnru qx56pjy e 1.imes higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properlh 7jri8nq5/k7/ cialjy constrained by an over-the-shoulder seat belt has a good chance 5/i 8ic7kjan7r j/lqhof surviving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road below, and his pur(wei7.m* hp,sp hc g z9w8.zbysuers 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 wb(s.wzyz h8 ,ehmig7p .*9pc 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions 0p4hrks5h:lp cb+ 2trby hauling them up on a crane and dropping them from a certain ktph:4 r2sp +cr5h0lbheight.
(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 abouaownoyu64*35 wzy us: t $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins unifov/6p.kjse .ij;*i;lc+ah ch y wo1-frrm acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m fryrcc lj wh*fo ip+..sk ;ave6h 1i;j-/om 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 the v5cq6+ bo6 slowater’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the wa66v+ cblo5s qoter. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid t:nd-8c i d: u8ykm9sfcransit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations: d s:mn:u8i8fcdy c9 -k
(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 jtw4;e5(mrd i fish. Supp;w4(rjd5 ietmose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform 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 ball28+*h lq ebkif 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 put f*h8eiq2lbk +t 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 trly4.jvg5u8jhc ,9d d kain traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fug9 58l.gjjh4,u yvdcd kitive 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 c y8s sw:z)s i7cun-x*u-csv: l2fo*nof a high building. A second stone is dropped 1.50 s later. How far apart are the stones whe-nf -zuscswv ins::* y2ox )cul87c*sn 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 cied1dws.y3m g6zx0eum0 dnb d 6w-3 u4ourse of a time trial lasting ten laps. If the fiz.3nbd0 -x 0mugd3sm6ddy61 e4uwwi erst 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 w(g9.bu1 69askhyutr9xi; qx) fz) cb 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (in cx gbqrxb9au(;h)st zy)iw 9 61u.f 9k$m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bounce 56y x+ecr d/sxy.zot8up one-and-a-half times higher t+xyozc. x8 65eyt/sr dhan 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 overrgjt6 orusvm554 : prd/n,yq3takes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What arruvpgt6:j 5 /rq s,5or dmny34e 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 wip.m1y7sd0 rq4ik:u 4 wq2j qilth a speed of 44 m/s In throwing the baseball, the 2psj qluy 7k10wiq r.44:dqimpitcher 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, fr4nj8th9y9 wo som rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–p qi3saf/o:,xn bny* mskg.gw8hqt9u p/6 2+y42. Each intersection has a traffic signal, and the speed limitxsgn tupbkn8q2 * p3 fiyya+/mos,q 9.h/6wg: 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-p:tdjyk n )k8 takes off in hot pursuit. The police officer catches up to the speeder in 750 m, mainkpy-:k t) jd8ntaining 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 bu u,;g0 jbo4b+euq-xj jilding; 2.00 s after that, a second ston;bjxebj0ju4q, o +gu -e is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone is tki603 ,h)mn. i:t r-hphdijothrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the groundd:kih6m-tptohnii r h ,)j03. after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long w8 3e mvni( 9frf)vgsa.ould it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 3)vrv (m3si.e nf ga8f950 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to)f4 tv+c 3xffc 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 fa+c 3fxctf 4)fvst 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 nul/yw.ih 0 m2 -bvxz2many times higher will Bill’s bam0zl-bv n.2ix2h wuy /ll go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the grlcm/8llvs1p6 ound 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 then picks up 6ml8vscl1l/ pthe 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 tlk ;x ,ztzlk40vt7dg6 o find 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. How much difference does tttvg7;6l x0k4dkzz, lhe 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the p*/oj)g/s8/4a dxm ke*dm5 zbuycl:wkosition vs. time graph for two bicycles, A and B. (a) Is there any insts8d5uka ybz4 /cm/ emk*:jox lg/wd*) ant 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 bicycle has the higher average velocity?