Does a car speedomet amr 21axtt:*i* b(qpver measure speed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, give exa:lvji s)a0m5u v dro9h:udvn- y6v2f ;mples. vor : ;u5d2lm9 yv0sfjid:6v)vh-nau

When an object moves wittmyii ;g dw),2h constant velocity, does its average velocity during any time interiy ;t )m,idwg2val differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with ther93c s.ysrcb( greatest speed crossing the finish liy3r(9rcb c.ssne to lose the race? Explain.

If one object has a grear;+t3bj r0;yp ahpe t. cc)km+ter speed than a second object, does the first necessarily have a great;pk3+mcecrp+)a 0b thj.yrt ;er acceleration? Explain, using examples.

Compare the acceleration of a moh pg oec13o( ;pp-fi(atorcycle that accelerates from 80km/h to 90km/h with the accel(-phofec(ip ; 3gaop1eration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceler2bekyz8 a,p cl6 jz3s5ation? Explain.

Can the velocity of an object bewo3yy7tk)r ipsokh )g. -8j5u negative when its acceleration is positive? What abjo-p8s3ukw ihy).k r5y o)7tgout vice versa?

Give an example whereuh f*t*hsl79 h both the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is tral8gr9wjj+ culz 7b8 q,veling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed o87 gl+9zq cr bj8u,wjlf 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its a5 d96el cs+qvxl ho z4pq/8p:rcceleration decreases? If so, give an example. If not, exde4:rp8lc +/ hxql5s q vopz69plain.

A baseball player hits a foul ball straight up into the air. It leaves the bat lvwz-vmh5/ 2s with a speed of 120km/h . In 5vvmshw- /z l2the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object spem p5t bie oaxr:;c9:gy2)jdy5 eds up, what is happening to its acceleration due to gravity — does it increas59 atyrpeio g j; x:bd5m2y)c:e, decrease, or stay the same?

How would you estimate the maximum height you cvk7l4,ev6z+ xtu gv(sr:yw4mould throw a ball vertically upward? How would you estimate the maxiuzt+ sl,m(v4 e:vkr6x4 gvw7 ymum speed you could give it?

You travel from point A to point B in a car moving at a co1:0niv6m s1wuk/d )7 cyhjnoknstant 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 a7ys k/n1:dmhck0)wnuo6 jvi1 verage 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 wit* 7ogh6c m2y:kha-q teh ten bolts tied to it at equal 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 6m-k27q yh:ahoe* cg tsounds 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 cw zmgv.2vg31 acceleration: a rock falling from a cliff, an elevator moving fr12gwvz mc gv3.om the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its origina*o;u8 xmkq ak,h7 no)al position with the same speed as it had ini ;,xa n)*ahoou kk7m8qtially 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 accelerr y xnc1tgiqgn0+r48*b(qjr/ ation at the same time? Give exagqx j/8b1(rq+0 * nrin4tyrcg mples.

Can an object have zerowei0h na ;+qy) acceleration and nonzero velocity at the same time? Give e +0yna)hiwe;qxamples.

Describe in words the motion plottedjtc / lbwk465/7wy9 tygpbh- u in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plohctbp6kw t l9w/uy574/b -y jgtted by walking or moving your hand.]

Describe in words the motion s. .-ax 7qmu3f4zxe;rz 4zzj1e d3te wz tq9-oof the object graphed in Fig. 2–29.

  What must be your car’s average smvy:hdqy 3ho;zxym5v.-c4 j 7s )dn+lpeed 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 1 *cdt5 dps3p-b5 km?    h

  If you are driving along a straight road and ym ul(6: ejh:lmou look to the side for 2.0 s, how far do you travel during this inalj(muh mel6:: ttentive period?    m

  Convert 35 mi/h to n-cu3k5j+dkb, loat5
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves spjsv(t/jb 3c -r ls-:from $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

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

  You are driving home from school st+s;k +hl:/m b.u rwafs, d)rj+rs(ugmeadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 minutes. rj;wk a+umfur r+s()+gsbdm,s:l / .h
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-ofb7v q8;dm9 n afs3rcw((e2p ks-thumb, every five 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 essentially no time at all, estimate the speed c;vw2 (ed(f79kpm snaqr 3bs 8of sound in m/s from this rule.    m/s

  A person jogs eight compkxy7 v6/ jfzfaciy b2s.)*lm(m) :ua glete laps around a quarter-mile track in a total time of 12.5 min. Calc z)sjxiylf.72 )ma(v6m/g*:f bckyu aulate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straigc w1nmuj16ew ,ht line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfww6eumn c,1 j1way 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 2sbv9p(sgmp. parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initiallybspv g2.s(mp9 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 behin .boei7iuy/sdkr +*j0d a truck traveling How long will it take the car to reach the truckiyksr07u/b+ eo. *dij?    s

  An airplane travels 3100 km at a speed of 790 dfz(soy aj/wx;78wa ; ,cw-hh km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next wyfs c7,o;az-w8 (ahj; d/hwx2800 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 completq0mbp d:t:cg- e round-trip in which the outgoing 250 km is covered at 9-pgqbcd:0 :m t5 km/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 rf7y zihu p5cpg6)l8b 3 -m,dvconstant speed 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 speed of theu6 )rvpcg,pb- zy73 mih5fdl8 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 8ux1rz d0e b:7zmoudwui (/(s is its average acceleration iws7ou:(1zmuz/(xr iu eb0d8 dn $m/s^2$ ?    $m/s^2$

  A sprinter accelerates x7w cfils4 ttu70: h.qfrom rest to 10.0 m/s in 1.35 s. What is her acceleration x .7l40s utqfitwc:7h
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is clxv)i97u9p77o rs5czc -o u e wub3 jm-.;fdwdapable of an acceleration of aboutu7.d-w -)u73wso9cv 5;o79d r czfumxbipl je $1.6 m/s^2$ 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 cuxhh ;t( 2d7: 4wv28 6zfumatyv2zsnconstant speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 smzytndx u2u(;z2tf v: wcs74vha2h86 , what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 and m9qr**xr -mbdnc txr(xlp i71 *oves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its lr9xbr -ip t1nxdrcq**7* m x(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. Wt0 9gz(qqd3n shat was its acceleration? How far did it tdz3qgqnt(9 0sravel in this 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 its acceler);e81bhtf 3dds zg0 tq4 odhk;ation, assumed constant?ehgskt )8;;413 tzdbo qf0ddh    $m/s^2$

  A light plane must reach 5iz l6)lmef a7 qz*v:xa speed of 33 m/s for takeoff. How long a runway is needed if the 7ivl x m :5qfl*z)za6e(constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the b++; o2ag)mzlikp p.,sap on934bts orlocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of thl+9g+oo mt p2 3az;,.ksappns4)irboe race. What 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 fnge s h5: f.ru1 /syx3e5izp0brom a speed of 12.0 m/s to rest in 6.00 s. How far did it travel bi hnf503g. 1:rxszes u 5yep/in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assuming b/04 fq 3oxax4n ,wywcanyaq0xw x 4wbc/,of43 deceleration 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 i9+ uizn(zc2i front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during th z(c+inu 9i2ize 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 dwz:;x bsgb*f5rfd 1*w8jg a7;fgf 2dristances for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, f*z xbfr*:2j fbf 5drfw1gsawg7g;;d8or an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the 39( aj+xtmiga 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 goind*1gu.t j.n /ms 1nvkcg 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his /*gm1v knu1 tncj.sd .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 imeq. fa.uh jvss9kxg 8l84+1 less than 30.0 min. After exactly 27.0 min, there armafje ku8 9 x s+qghi81v4l.s.e 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 7ix tcp) (vo+van intersection just 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 xv+7(cp)vti ois 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground be ylbqq-: 1okm.low after 3.25 s. How hiy . komq-b1lq:gh is the cliff?    m

  If a car rolls gently (qf+u1tla 0 tuuq/25h w$v_0\,=\,0$) 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 stra bbwu p4:oevy 13e7bvqf2 wkp;r l+f71ight up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after ykq6fba;bw+e( 3v 2ld.4ua pathrowing it vertically upward. With what speed diwa3b d+6vu4e;2pfb (q la k.yad he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest acql ;-by*tn.s2 ffh 5uzh8 gd2gf1vu1nd falls under the 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 air resistafgh1;2 d2hbutucgy. 8qvznl 5s-f 1* fnce.

A helicopter is ascending vertically withmn ano)l3;h m2 lu1co; 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 package’s initia2n ) c1ualnmoohlm3;;l speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distbkwgu7i7)vd 8ro,(a a ance traveled during each successive second increases in the ratio of successive odd inte7u b8a7 (i,vdo)kwgra gers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is negl lafmyw )(c)ia+ qk*-bected, show (algebraically) that a ball thrown vertically upwaqkm(*ifcl )w+)ya -bard 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 m.,7 do gstlud5g st8r:e:q0po/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 in Fig. 2–18 (or number ov:d6* 0swpryy*5i9u : tkmq off photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple position6 0mrtyd 9 u*wf:pi ko:5*vqsys, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2–32)vpnno-4m .tkq w q ).(nykwy7). From what height above the top of the nv(oy.4.pyw7 -nq)t q k)nwmk window did the stone fall?    m

  A rock is dropped from a sea cx8c e8fwv ht;/hbop/. liff, and the sound of it striking the ocean is heard 3.2 s later. If the speed of /vo twb h8;phc.xef8/ sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust youcb6 8kft4 *ypgr 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 you quickly move the nozzle away from th8 byp4g*t 6fkce 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 12.0ir l2 vpt/h9u8 m/s from the edge of a cliffil9/ 8h tur2vp 70.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 22i b0ju lr t2aqz/1byc.v08j5:4w yig6s y hap8 m above the street with a vertical spee wb1s50 rcyl2.zh :y28a6vu0/gjaq ib pyti4j d 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 function ybh*1z7/k ) tpc;-eq 4pw r9hq nlxyg-2s s,nbof time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periodkpl7x)/ ,nw s4z9 hc-ybq ebt*h2s;nrq-gyp 1s, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight f8r8mm:7 ob cetunnel as a function of time is plotted in Fig. 2–28. What is its instant o878mb: emrfcaneous 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 z4kj/8*c:o 8j0uxah/m p dsncaccelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the hxdk8/zj 4u /o8n*pcas: mc0jgears.)
(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 accd a wz1bk ok (t83krnj-cl,lvo 06,6mweleration of the car in the previous Problem (Fig. 2–35) when i v 0o66kt1k3wk abdcl-z8wr,j (,mnolt 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 traveled duringob 6 9fz n 91.po+6:oqjagu)qqz oldw7h;, hkc
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a,rh)1-fl6vq syjeb +7yiw 9gs function of time is given by Fig. 2–28.e,j g rv)9qbf yhl1y6ssw7-i+

Figure 2–36 is a position vzr)za o(ky.n1 wd 7t;u+l6e gfersus time 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 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. ny)k ;u1ot zelr+d.zfg7w6 a(

  A person jumps from a fourth-story window 15.0 m above a firefight:wuey m8lr5 fk +;:jjher’s safety net. The survivor stretches the net 1.0 m before coming to r ;+ hj8jlyfmkeu5r::west, 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 c-eh2kc. -1u fpkqag /on the Moon is about one-sixth what it is on Earth. If an qcp-c2eku k./1agfh- object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the yc0:0s:st eg qxqc*n2-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed ab0:ec*0tcqs n q :2sxgyout 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 be* *kqcdm 2ofqxcu95 w/ xos *+ekie33hlow, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m a9cxiq5 3hqm oe2 *+*3/esfd kcx*kwuobove 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 ,/j.qy:t,:;frtl so o(gqb6h /xvbpe its cars for front-end collisions by hauling them up o /y/o:o(;pjb.l r:,h,bxtqgs fv6qe tn a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels a-bq)c )sw7md / :kijhzbout $10^9\,km$ 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 rkbh1l * /zn8h1pgup* 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 from where the front of the trgppnh lr *bh 811k/uz*ain 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 hx-4lr/d:cppw41kfo c*ru ,vkxb-o 9 the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of tc-4u/pxcr,4 fxb rop-9:k*hol dw1 vkhe 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,d,yqkelle- e/3m y:d* it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slm: edye,k*/qly3e ld-ower 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 winz2r/54w fvxp /a8ang ggs and free fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once 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 wgxv/f5raz2g8pan4 /of the water.    m

  In putting, the forc4zdz9ph 4uw+gm py )8d:qrw0 le with which a golfer strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting dowpqhu4w:)m+ g4w98drpz d0 lyznhill, 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 t8wk .koh 3pv8v 2y9pi 8sb0dvxrain traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from 8k 8hw 28s39i y vovbpxv.dkp0rest 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.qifj- x sx: 8to8j/nr. A second stone is dropped 1.50 s later. How far apart o8 :.-xxrjj qtinf8s /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 course 8) yajoua-rw 7of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what aver-wo)87 urjyaa age speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he movb8zj s2s*c6zz78r8a y nju d:res at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What n 8csa rjrj uz:78zd6*z 8y2bswas his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bounce up 0ed:u1cu zq5hone-and-a-half times hig :d015equuhzc her 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 ;usx 4yvr/ ::5zeg zvgkm/h overtakes 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 v5:vz :e u4zr;x sygg/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 bo1z 0 mu3hrb7nr +5e iv6*monfaseball with a speed of 44 m/s In throwing the baseball, 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 during the th zm 53 brnf+76v0hi*enm1 oourrowing motion.    $m/s^2$

  A rocket rises vertica;ckr r.ki7i*blly, from rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each intersec)f c ul; znv,egovn0o)q tf,-5tion 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 1gtcv qo;-,f nfe), )5uv0zln o0 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 ku./+ )cvlkb6vx :9yoec t 2okqm/h takes off in hot pursuit. The policv.ov ux)o+c6 2c le9kqyt/kb :e 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; 2.0ayrfy()y656y6v mvhofaa( e amm92y6 0 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same time. 6 9)vvfyem(a h5m a(6 oymyfyy6ra26a
(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 f sgd .l(gm92csirst stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground(2 l cm.sgdsg9 after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-falling 9 d+ hq-w(y,kz -shkjfa.hhy) 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 350 m? (In reality, the air resistance will restrict her speed to perhh h (.hfjwdh, y 9z--kks)ay+qaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the blpkcykg:2tg ek6zb q 6p(6((hurgers 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 (g6(k(yl b26:kgcezqph 6 kt pbelt 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 3 rx8 o,wp bf75d(yu :s7uzfxkvertically at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go 7x u8x73fso5 (prd zkb,uywf:than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of apks/a j1 oa(i1 cliff 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 then pick 1(sao/iaj p1ks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular building usinf 9kgb k z*kna,qy1k. tad- k;fo+l52sg a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and dr-sfd ko*2fl ,gt9kk5bq; k+znya 1a.kop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph fj x a:f15:jp :q /telueoe*wi5or two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other?:fp *5jea/ o5et wqi:1lx ju:e (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?