Does a car speedometer measure speedni sj6r71c-8ao wex n-, velocity, or both?

Can an object have a varying speed if its veloi us g,. :yozwv.1v-qocity is constant? If yes, give examplu:o oqyvz- v.i 1wsg.,es.

When an object moves with constant velocity, does its average velocity fei0f 2o j.h cen384scduring any time intecf3 hj e.8n2eof4i c0srval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crost24mq 8xk1y3w4 -di rgudq5 rwml9 u5ssing the finish line to lose the race? Explag9 uwuqmdl-sr 4wy15r5 kmi d24x8t 3qin.

If one object has a greater speed tfa o 6fkrv;ev8o0q*9 dhan a second object, does the first necessarily have a greater acceleration? Explain, using example69vff;d kq vorae* 0o8s.

Compare the acceleration of a motorcycle that accelerates from 80/o/po kx7 y :ge6p: et)zakv5ukm/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the same time./kev6)egtap :k5 o: uxpo/y7z

Can an object have a northward velocity and a southward acceler8)v;s nu6+rfkd5rys q7k dg2 : ioj:ghation? Explain.

Can the velocity of an object be negative when its acceleo,h g+rh7raubed pd4k,4o r74ration is positive? What aroohkra7 eg,db, 4 p+7ur dh44bout vice versa?

Give an example where botn epda3hnj 3/1q*xh5vh the velocity and acceleration are negative.

Two cars emerge side bzy(vtu v0k1q.zg j)gon m*)f:y side from a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration v: v *)1(0 qztky)fz gj.gumnoof 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If sjj/m gx(5od ep 0aj,v2o, give an example. If jdj0 5g2o(em px,vja/not, explain.

A baseball player hits a fouu w(9js6,m*+ iw fesolew5vl8l ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistaje 9w8fl msi65*ous+w( v,lewnce, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its acr4adxfv;v+ ojglz )3 ;celeration due to gvadzx +ov3r j4 ;f;gl)ravity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vec js u 0.pbynfa7/c929o5lr gqrtically upward? How would you es 2pq ynaobclgc0/ 9u9fs5.7 jrtimate the maximum speed you could give it?

You travel from point A bxz7s+sl 7sk,r lvby8/ap-m/to point B in a car moving at a 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 entb m8-byv 7,xkz7r//sl+as lp sire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstrationux2caput;;6 1p s:qy142p obo:j zxkp , a 3.0-m-long vertical string with 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 sounacj:1q s;x1oputbp4z6 2uk:yo p p2; xds 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 acceleration: a rock fa bwx2b p 6mrmcw*1pvg-21b zh0lling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting onw*z1hvmpwcp2g106-mbrxb b2 a table?

An object that is thrown vertically upward will return to its original posq9*twxs0) 3ua avrhr cw5,)t sition with the same speed as it ha0tw c5urhstqa,)a v9)3r *sxwd initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and no;mifz 8wmegtpx6ykb i6)f 25uy)a /4jnzero acceleration at the same time? Giveixakfgy)ib/m5j6tpufz 6e4;m w2)y 8 examples.

Can an object have zero acceleration and nonzero velocity at t1cgdl8j c 0p,ohe same time? Give exac81jcopl 0g, dmples.

Describe in words the motion plotted in Fig. 2–28 in terms 1h 2 j6qjttzg4yf )y*sof v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving1gyy26hfs)t*tqj j4z your hand.]

Describe in words the motion of the object graphed in Fig. 2–29. -t4u.fc5tvcic ooy8v4ae f3 3

  What must be your car’s average speh,t;x8fv +/sgwg7 ci0 feya;z ed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How lonkm6ogcy32 wd +g does it take to fly 15 km?    h

  If you are driving along a straight road and yowzv2n nn; n9b;7znmru5t 5a3 ou look to the side for 2.0 s, how far do you travel during this inatte rn ;n mzn2 tv;w5z35b7onua9nntive period?    m

  Convert 35 mi/h to o4r mcyrx zcx. iu)8+3
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from9su2iurt qm;3pch b3) $x_1$ = 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 for 130rwra i r5 ib-)/.r2(mglsz9v l km. It then begins to rain(l.i5rgml rriaw-2b9 rz )vs/ and you slow to 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every fidy+fs ib7adb. fpq9+ 6ve 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 speefpy fad7d bb6.+ is+9qd of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in y+r +,y lfx5jgutt*1va total time of 12.5 min. Calculate +*lyjr5vuy+ t x1g,tf
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from 9vxnwme o4 .w:yy ws0*its trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway bes w y9v0wxo w4.:y*nmack 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 parallel tracks. Each has a s*wt m3.czx o5o76xaorgqs 57mj4kp z 8peed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30). 7kr stj xwz53o * 54m8c.agpoo7zq6mx   min

  A car traveling 88 km/h is 110 m behind a truck trax 4 bkvrw-4v6.wh u8bmveling How long will it take the cax4 6wukr b4.-h vw8bmvr to reach the truck?    s

  An airplane travels 3100 kmjh98g2cf-.s rpc8kl r at a speed of 790 km/h , and then encounters a tailwind t8.jglr2k -8c9fshprc hat boosts its speed to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average veloc k8 qt aikcm7w*- z64r+m5ehraity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the retur+qri w-zhm7ak a4 mer c86*k5tn 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constaro ;u *6b4u ;nqgji6hont speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound oou6b qg;ui rho6;j*n 4f the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates fsmgj9 s(g 7 acq4b f6i, l5ncads;5o,srom rest to 95 km/h in 6.2 s. What is its average acceler(sg sqc 75li 6mofgj;,cs95 ba,s da4nation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.ln ib+bxi* ah h*8ax5wse-0sg-y+ 5 wk0 m/s in 1.35 s. What is her acceleration 5ln-aa-++xxsh i*hg8w5 kwibs *eb0y
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capablzwkq u7;,w;4:r niizt e of an acceleration of abouti zw z:w;,t7kr qin;4u $1.6 m/s^2$ 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 travewltv0ymvv yv o*b1*uup5e ; *4ls 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what m ;*5vy0lo*b vvp14*u wytveuis 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 dqa/,x r, u9s1 .f5 hd;wusjmjmoves in 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 and on a x 5,s/dwjsjf. 9h,ru1um q da;graph.

  A car accelerates from 13 m/s to 25 m/s ib6xs.xnr(r: h n 6.0 s. What was its acceleration? How far did it travel in this time? Assume cons6.nr xxs:b (hrtant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest ihx)5 (cmnvpn7d es7 b;n a distance of 85 m. What was its acceleration, a77 h dspxn(mec b5;)vnssumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s m xd2,j 3pb1sudyi6-wfor takeoff. How long a runway is needed if the1m pddw y,6jix- us3b2 (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of tel+v.ac1 :jily kh; 1ehe blocks to essentially top speed (of about 11.5 m/s) in thve:j+ky 11 c leilah.;e first 15.0 m of the 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 from a speed of 12.0 m/s to rest in 6.00 s. How dno.ce2,v,kbfar did it travel in2o.bn,d c vke, that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highw.4n o61aey/cv9 ty uvway. Assuming a decelerat ea v 9cwuntyvo6y./41ion of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compresses 9ac lku)s syn9l ;o g9n5lnvs9u4xk .2and the driver comes to rest after traveling 0.80 m. What ;)uncvo9ls5sk9us49an2k ngy l.9lxwas the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with a.wn tr1q.tc*u: 8pqsw n initial speed of 95 km/h and human reaction time of 1.0 s, for an arp8 tc1q.s.twnwu *:qcceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation fo59iw bd9twxq :;0iv 30kyxi f jjem1w;r 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 going 25 sd- k a*/jkn*+iqnp+p m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car+*a-ds/ p +jqk* kpnin 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 mlz 9ax u+8ois:in. After exactly 27.0 min, there are still 1100 m to go. The runner must then aus+:i zx l8oa9ccelerate 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 i;tdvi iq y sh9p62u1:just as the traffic light turns yellow. She knows that the yellow l ut6yvsi i9:1;i2dphq ight lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground below afte+r2r5fo.qt/l3kmlrxkkv6 q- ruk ,:er 3.25 s. How hig rqeol krl /vq kx6kk5 2ru:-t3.+mr,fh is the cliff?    m

  If a car rolls gently ;c. v eh)6ol m+2u1ddh)3;p obkkuiet($v_0\,=\,0$) 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 s/b7. yy ijve;po+pg/ntraight 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 throwing it vertical(ly/si l/ 0n m65+qero;dwajlly upward. With what speed did he throw it, and what height did it reach? 5mwrd0l l+ ;iyjs(neq/ 6/loa   m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence ol(8 pq1zrcsw,w 6tomv/n.* dc f gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a fu1q.s tc,(*w6o/8 mrdv ncplwz nction 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. Aq/ nfu:t+fntc7b0: sut 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’ss0nuftub7t+/ q:n: fc initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance travel tsi5i g/nek(3vpy1 c4z+ vg2red during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was firsgce y35(4g ivsvtzir1pk/+n2 t shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown vertmsq onnt/g- 95ically 5ogm-/sq tn9 nupward 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 sp obgkf/59ihbo-nw 1 -reed 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 apple in Fig. 2–18 (or numbdzo4bt m,q(n0er of photoflashes per secmo,b4 0(qztnd ond). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s t--u r;fzeieemvr2 6+lo travel past a window 2.2 m tall (Fig. 2–32). From what height elf+i m-r6vuz2e-; r eabove the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it s3fmi, :5s)yrugm .ccutriking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how higfc:umr5) c y,sum. 3igh is the cliff? H =    m

  Suppose you adjust youoyy (ru*:qs r g+hs).5udv8u kjp-u 0mr garden hose nozzle for a hard stream of water. You point the nozzle vertically(q r)ousm.0uuuyd:j*g + -svp5y 8rhk upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the edge ofs83+xpe*tquf44mhdofcrip 2hikbk68 x ). 7a a cliff 70.0 m 4ik28 4 38kxdf.)uitoh+ b6c7epfpq rxhm*ashigh (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 windogit cx(i i,e0q(;cs3 hw 28 m above the street with a vertical speed of 13 m/s If the balt i;i3ch, x( (secq0igl was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocit.h/jtg; qj7 isy of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitj qs h;jti7g./ude of the acceleration greatest?

  The position of a rabbit along a straight tunnel a0mbqjb bm .gj53 whs4:s a function of time is plotted in Fig. 2–28. What is its insgmbjb40q5.hj wm b 3:stantaneous 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 automobjf954 )xx:jeb 4g h4 2h;gdz0yvfj caiile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.) 2xjd;hcjg0) 45y a4f:bj4gef iv h9zx
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Proble: xp8wrt*kpk5 sg;xs3m (Fig. 2–35) wsx*;kx 5s:wp8trg 3 pkhen 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 traveled during,bp yd6 z9w*br
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a function 92.ul2k7 + )hepot; 2r(ejwrtltufywof time is gk+ r yl r29wlp.2;o2(tfee utuw jth7)iven by Fig. 2–28.

Figure 2–36 is a position versus td.s8xb rlx.k e, 2qokc8 u1)exime 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 forbk2ulex x).r.8,skqd8ox1 c e the time interval from C to D.

  A person jumps from a fourtki /qw8.q* fcvx pu qn4i;smfoo3j7q5);l :fch-story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–3*s:nvqoq )w; qxqmpk ij75 3;f o8cfi4cuf./ l7.
(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 ona8-o xrs ur)o. Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming ther)8sroau. -ox same initial velocity?

  A person who is properly c24v kqdg56h cmonstrained by an over-the-shoulder seat belt has a good chance of surviving a4 gqhv26d mk5c 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 qxmx xt1))w c,bridge, 12 m above the road below, and his pursuers are getting too close for comxm ,)xxq)w 1ctfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its c6unc 1,ryxth, ars for front-end collisions by hauling them up on a crane and d1r ytcx,,h n6uropping 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 abouurts1u zg:kdlu:5 xr7*f* 6mh 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 unifo oy+ai2kbnwe 1:9l x-yu(efc8rm 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 train started. What will be the s( - y:+ki8e9lfy uwb1eo cn2axpeed 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 wat +6q/pck0nl 0uh b;fguer’s surface into a deep pool. The person’s downward motion stops 2.0 m below the suhu 0ck+;/ln bupgfq60rface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balance thk+i/ t,k 5rw7 nialb)re 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 9tkiir,nwa +/ 5rklb7) .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 wing 7l+r2 f/,b. p4tiic zvnbwdw+s 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 pe/ 2n7ri.+ zcdf,viwlwt pbb4+lican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planjkgr :zp:wngq+6v8 q4z ha;d, ned 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, putv qnjhk;z:,pw4r8 q:g+ dz6 agting 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 traic/y333b8w egf0w yhh zn traveling at a constant speed of 6.0 m/sh3/gb hyweyw 03fc38 z Just as an empty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof ojln0n k/ye m;b0 jw8pg.kt+;qf a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the secol t pjgy/kn+.b; k;0mqj8wn0end 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 time trial lastiubjk8m abf(+: ng ten lapsab+:j(uf m 8bk. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Toui;qyx n gh* ;-gyec.f+r de France crests a mountain pass as he moves at 18 km/h . At the b.nhq+ fe; ; i*y-yxcggottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bounce 2u(zh9o v.8pqumvx.2 qawyllgg4+*nup one-and-a-half times higher than the second child. The initial speed up of the second child isa.v8y zl.vm(22*ug9gwxq hl qu+ p4no $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 traveling kqm3 b; 1i;eniwdz:q,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 e,1 qwzib: 3;imnkdq;in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In g:a c0sggc-ibt dko(0le5n i(6lk .*cthrowing the baseball, the pitcher acceleratesc0-n: c.ektcg0d s5a6l(ki*bo ggil( 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 rest, with an acceleratj2janm:rly k*hu;0h 4w/wmr1 ion 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 show(l5e.xpv t(yhn in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights arp h (vy5e(.ltxe 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 ty qt4wd(fk4: at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant accele ywq4df(tk4t: ration.
(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 to-1ho;t1o- cyvl7k th he roof of a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones lan7ckhoh1o-vl1 ot- t;yd 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 verticalf awhhm9i0+ bx(2dvb7ly up at the same time. 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 what initial velocity should the sec d(9v2 xm7hbf +ibwh0aond 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-fall6+e: apd9lm*0vddx vr ing 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 xa r6v 9*+ddl0m v:pedto perhaps 150 km/h .)
   s
   km/h

  A fast-food restauran. 0me5pgvnhlf.,*vw g h6tek5 d21hzz t uses a conveyor 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 c,gne2te lwm0k5 zpv1hv. z6.g5d hhf*onveyor 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 fasy08 v:u ,v0ttoa +jlguter than Joe can. How many times hig :y0utgt8+vv la u,jo0her will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your f 8:o: d 0uuox1wiln6zmriend stands on the ground below you. You drop a baxuniuo8w0o lmdz1 :6: ll 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 the height of a particular buildinwe 4hhnt1+ yy/g 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, anty e/y1n whh+4d 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 for two bicycles, A and B. (a)fowyu.1r r1.7v9lb zi Is ther.1bo u 7ir1rl.zy9wfve 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 bicycle has the higher average velocity?