Does a car speedometer measure speed, velocity, ryo6z j2m-8 9 yvjc1qdqikw+. or both?

Can an object have a varv bzavj;:e1uvgx;fqns5 0b,- ying speed if its velocity is constant? If yes, give exasb,5nuj;vz;e :1 vbaxq0vg f-mples.

When an object moves with constant velocity, does its average velocity duriabfp but+x56 he+h c53q;y-xgng any time interval differ from its instantaneous 3 tyx+;-ph6bbgh q5fu c 5xe+avelocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossinymps 7c;vi;-z g the finish line to lose the zcp;y s7v -;mirace? Explain.

If one object has a greater speed than a second object, does the first necest +e kciji/ 1pam-cbp+ ur ;;3n2j9wzgsarily have a greater amtj9unp/ rz-cwaj 12p+gkibe;; 3+i ccceleration? Explain, using examples.

Compare the acceleration of a motorcycl y qs9z8 vhc2rm2+ta5te that accelerates from 80km/h to 90km/h with the acceleration of a bihqmr2a+9v8czt t 25s ycycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a soutq 3,r avskeru9.8 ;5vut 4pmbthward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is p - -om3rs pn0p*7fovn.(bb zfzositive? What abou0pv fo7z-bmfz npobrn.( 3*s- t vice versa?

Give an example where yn2vktu f8t8lu o*t1 .both the velocity and acceleration are negative.

Two cars emerge side b6i,ow)g83b p 0cnj) q5jzr oqpy 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 of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain y,j 8nj65wrp)b c0)3ogzq oqipour reasoning.

Can an object be increasingl s(7syyi 2b0j in speed as its acceleration decreases? If so, give anlij0y (7by s2s example. If not, explain.

A baseball player hits a s be4lceh; k2::q lj* x/2boxnfoul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the q c sol*:4he/j ;b2kblxexn:2absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speede7p qgt0j37)xb qi ji,s up, what is happening to its acceleration due to gravity — does it increase, decrease, or stay the t piq)gi7 j7 jb0,3xeqsame?

How would you estimate the maximum height you could throw a ball verkn o.hnmwe m3f r15(m.tically upward? How would you estimate the .fm.m eh on(nm3 kw15rmaximum speed you could give it?

You travel from point A to poinfaw da) gb ;1t*e+y:zlt 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 : a*agfl+zb dwey);1tof 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts tie ev: dum4vo: q(h4wq,sd 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 sounds will not occur at equal time intervals. Why? Will the time betweendhuq ovev,q s:4( 4mw: 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 constvxh ,7fg,m h+qr;yg1gant acceleration: a rock falling from a cliff, an h; gf, rx, 1ghygq7+mvelevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vvt c+)sx jnt 7* -1efxtq1arj5ertically upward will return to 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, how? [Hint: The accelerati+-1 q )vs*1rt 5tnctafxjj7exon due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nont *wugjn g)9:7 +rn*pufy d3uazero acceleration at the same time? Give examplesu*wn9*n) 7 tf 3aygrj g:dp+uu.

Can an object have zero acceleration aa zf86:o8qkml nd nonzero velocity at the same time? Give exa q:zlf6am88o kmples.

Describe in words the motion plotted in Fig. 2–28 in terms ono8h* 9 6xqbruf v, a, etc. [Hint: First try to duplicr89 6*hnbqxu oate the motion plotted by walking or moving your hand.]

Describe in words the motion of the y07sz(cpp3gn we8 a o88d uj-wobject graphed in Fig. 2–29.

  What must be your car’s average speed in order to travf;gem sc,c/wv nzb)( 9el 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 kai:i) -obmep4k ) 4/-nwvu,9bd qwl fum?    h

  If you are driving along a straight road andcl /gs6p 5ke7 q/f(f.adk-m- xvxjv4u you look to the side for 2.0 s, how far do you trak p/cdv.fea/s -7qxu5vm(4-lgjk 6x fvel during this inattentive period?    m

  Convert 35 mi/h to eyrfgs(1k w *8
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fro curw n f4:th0ab6k(b(m $x_1$ = 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 schoympnnn8 ,:k-q fwn8f3 ol steadily at 95 km/h for 130 km. It then begins to r pnf,8f8nw m:-ynknq 3ain 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 five seconds between a lightnin9m( lfpes u4w/bp,e: ;xilij 2g flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives 9ixeu/ s4ljm;ppl( 2wibe: ,f 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 around a qpudp z:dz5 j* 0oe(n :,h(kqjvuarter-mile track in a total time of 12.5 min. Calcula jp zzk:dn( v5eq(p*jdou0,: hte
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in g pjqjj6c(2 7z 59xdnaa straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallopnxqj6g(a7jc9 zp25 jd s halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives appr6j-pwou jwut :d8)y 7f pi(oayyueg2tb(0- (uoach each other on parallel tracks. Each has a speed 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? (Sey aybuiept dyw8(twojuo6j0u-fpg(2)7- (: ue Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind awu3 )lg-etbe3q sgj1, truck traveling How long will it take the car tg 1e,-t3 )l3eqgjwu bso reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounteb hfziy 8o98 nh,nnm .117le21jm ithors a tailwind that boosts its speed to 990 km/h for the next11j7mno i fn.bh9 18nze8m,hlty2oih 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 /nl4roz9b b:gspeed and average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 k/nbgo9b 4:rl zm/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 speed hits the pins at they61do3 3vfbxpdy0l9x . cz8f h ycs14i end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 mylc1hx0d4 c9dzfy b 3viy 13s6.pxf8o/s.    m/s

  A sports car accelerates from dgg 51 uvjlsku-( , )ur6.jxkrrest to 95 km/h in 6.2 s. What is its average accelerat j r.kk(uxgg,)-l1 u6uvj5ds rion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates fromjn.d /;3 ky/z zkly*9zexl ui( rest to 10.0 m/s in 1.35 s. What is her accelerationyyuz.*/kllki(z9/xd e;3 zjn
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capaacn op lxis8l gm np/7*sc9in371j9+ xble of an acceleration of about lcnm9 x17s9p7ipcnx /3gnoas lji* +8 $1.6 m/s^2$ 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 tra9c.wcoonj7 p9 6)+sn5sfz cu) gsti) uvels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its acceleraticc nu .z+cn)o9w9sfi sgo 65sp tuj)7)on 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 racutk5 9esl byw-y;j p*blcm(,8ing car, which starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table.*yy-8tsmekbjpl;uc wbl9 5,( 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 inkf-skb u kh+4v;a4te04x btk- 6.0 s. What was its acceleration? How far did it travel in this time t4bkav-k4- ;ef4kb kt+ux0sh? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m.(1dcv .kp6smh:z5 f rq What was its acceleratip(s5v.6r :qc 1dz mkhfon, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoffl (y*bsp( g)qlr)3imd. How long a runway is needed if the (constant) ac ys(gl)*b)qp3ld im(r celeration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top spx) v,1ttl)ezm eed (of about 11.5 m/s) in the 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?z1,e)mt vl)t x $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest ce: 3)cnhk g6sin 6.00 s. How far did it tc6k :cg she3n)ravel in that time?    m

  In coming to a stop, a car leaves skid .rzn+ ks6qh4)n jz,ifafmb) ; marks 92 m long on the highway. Assuming a ,n kn.b4fq jzfaz+ s;) mi6h)rdeceleration 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 ofq7w b7;kny2 h-h*ilwf the car compresses and the driver comes to rest after traveyq -h ;bh*2w7nkf 7willing 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an in2u+ x7ot t-kwu7si)kq8uh de5 itial speed of 95 km/h and human reaction time of 1.0 s, for an acceleration t5uewi2 8-x 77+ust hkd)ukoq
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance ov.l,k2oms zs1u46m lug( tb,o f a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s driver looks liu;(hen:cp7s0 dav, for an opportunity to pass, guessing that his car nl,pd iueh(scav0:7 ;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. After exactlyjw kubf5* bg;tj 9 fvk3vr122g 27.0 min, there are still 1100 m to go. The runner mubg vbk9jj *;t52 k3f2fvug 1rwst 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 4m-pvx meftx1 6kp 87+qw 4uyw*5 km/h approaches an 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 iq4 8xemxpt uv 1-w7wpmk6*yf+ntersection (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 aft yia3-a0i -fx ak5puz4er 3.25 s. zf3--pi uayak 5i 04axHow high is the cliff?    m

  If a car rolls gentl2fv - aa1mbc;ay ($v_0\,=\,0$) 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 near13dt):wpfn6zg5w1 )g;.hd pmy*ifjxynryi( ly straight 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 akq;o.oqq v3h 1 ball 3.0 s after throwing it vertically upward. With what speed did he throw it, and who. 1q vohqq;3kat height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the infv.x j )x9r2eubluence of gravity. Draw graphs of uv )j2xb erx.9(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 resistance.

A helicopter is ascending vertically with a speed ofq )ejqo8tv emj(s34o . 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from ooej t)q.mq (3ej4vs 8a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled duriw0r vv(ex:y3 nng each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–2v:0e3yrvxwn ( 1.

If air resistance is neglected, show (algebraically) that a ball xh+ hpl pz ;oerdq1-8)pd47)dw,k66n g sdnjythrown verticall n pz+dgjkpxlyhrhqd4-n1 ;e)6s, w68d)o p7dy upward 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 ww xj8f (c9mqq)ith 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 apple isd+7rrow-9 famz /fv/ a ) tp1v;j4ec ;z0giyqn Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 100arvt/;amj 4r7 ;zo dw91 pf/q -gz+c)sievyf cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2h.t1+j6hep*t6ma cri vi )9w i–32). From what heige+cam6hii*j6 t.vw 1)hi pt9 rht above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sou-zey)nhvocdgap qoa. ,wgh0+4 yu 7xx f9 ,b)9nd of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the c,c)e +-4 ubyy99zag, xhhp7qf0on owa .g)xdvliff? H =    m

  Suppose you adjust your garden hose nozzle for am- pjq) hq-bqvnrd822*ad* b4ca d 1py hard stream of water. You point the nozzle vertically upward at a height ofyv28a nq*1dqpd 2- 4 -baq)p*mbdjh rc 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 of a h* ilmyud(,b 2g)7xbkcliff 77m2xb gld(,*ykb iu )h0.0 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 28 +fm5a w+m2e hmm above the street with a vertical speed of 13 m/s If the ball was thrown from the streee 5f+ wm+m2amht,
(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 of time. (a) At what jqm jb2.8ttr5 time was its velocity great8j5t2 . mtrqbjest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of ti c: 9ntn7zs7xvme is plotted in Fig. 2–28. What is ittnxsvc: z797 ns 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 accelerate approximaten zk 0zi9lz7+ h)i8uce2jrid .ly as shown in the velocity–time graph of Fig. 2–35. (The short fluld.90k8+ne ii2c 7rh zjzzi)at spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previoiw;n+)- h.uimguqxze 1m)t 8xus Problem (Fig. 2–35) when it is in himge)muq ztw -i8.)+nx1ux;
(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 dista zef80 im*4iwdnce the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object wh5 ;fbum/fg eegw0x ll :8mkr im *1o4i5thra+.ose displacement as a function of time is given by0g 8wff :im*.5rg/khia u4m o ltb erlx+5;em1 Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an object al b8fauv(ob2d2zv9 l4long 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 intevdufv8zloal94 2b2( brval from C to D.

  A person jumps from a fourth-story window 15.0 m a,h-e:y11rtr ut9sbo ucu3br,bove a firefighter’s safety net. The survivor s1:3 -rb1u,ho9 rt, sbu tyeucrtretches 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 Moo pniseowqoa9c(4,e umwsr3 .- 2 ,mx:fn is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the w-o(:ocpxr3qsfe i9 ,.un ewmams2 4,same initial velocity?

  A person who is properly constrained by an over-the qxd;mr y 3:1lm xx*s)ljhq:l2-shoulder seat belt has a good chance of surviving a car collision if2 sqx:3jq*lx;xmyhml:lrd 1) 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 a0 ( y+hg3*qa 2vh+a9 tosnp ow5f-;vkx-xjstn bridge, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The 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 dsn -p 2 vj-5 0ot;(ngvswofxqyt xhh*k9+3 +aaown from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for fronbrz*c qpgvec/n -*3 vhfn 4y,6t-end collisions by hauling them up on a crane and dropping them fromn vpn,*g34cvrq6z-* ecbhyf / 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 travjomi8 s(w4sr7e7 ,blppye3.h +6 fuqlels about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from rest. The front of the tra 1dewu9zk+u,ain 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 speed of the last car as it passes thd a+ew9u, 1kzue worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s sm3 rgnfqe50uv eb/+o3nidgde5.u8 l tay-i8 * urface into a deep pool. The personl+ggumi5enu8y5voe b3er/* -qa8dd0 i3tf .n’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessaiyx2p y j+2xt.ry 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 t.j 2xyypxi 2t+his problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fa:hcvz-7umi jv/xh:hwd z65rx8)dc7zwd c ;;f ll 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 0.2zc; uzdw x5i7 zfcj:v-h 6h7 r8x:vcdw/ )dhm;0 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 gol,aybkn cmt;4ksflk;2 x3cos fy.+..kfer 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 downhill, see Fig. 2–39) is more difficult than from a downhill lie. To ,sfbo .aky4k + nl3..scxt ;c;k 2myfksee why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train travb 5-8v 9ortqimeling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and accelerates otb8 r95q-im vat $a\,=\,4.0 m/s^2$ 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 om7,,jz .ioci; 3 :qwdltpqld .f a high building. A second stone is dropped 1.50 s later. How far apart are the stones. 3l ;zdcqiq, oldpwi.7,tjm: when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 20/8.rj bq:icm b0.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed m .i:/bc j8bqrmust be maintained for the last lap?    km/h

  A bicyclist in the Tour de France,+9 /exe +keiiy/:mbdvux y+a crests a mountain pass as he moves at 18 km/h yi kyve +++e/:e,9ixdmaxu b/ . At the bottom, 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 upv-o:hjwl feqp 7)96 7abpip t7 one-and-a-hlv i-6 jw 7p:po7ea 7pbqft9)half times higher than the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a7lbb fjb+t)2fv(l+90vhjv m d3 k1id n 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 are the results if the car and train are traveling in opposite direction1d9+ 2vnkt bf vb+ji(l)hm30v jd l7bfs? 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 b dborg9o m.20caseball 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). E20 or 9mgob.cdstimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accmr bta fn)a457eleration 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 intersection has a traffic5qe+p4 qxkvzr 1j3hs ;/c5zpx signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 svkph4qz1/ xrcqx 5j 53;+zpe 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/y o4hw hwr4b4c+b 5vg7h takes off in hot pursuit. y4vobg4h 4+wwh 7c5 rbThe police officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s aj(b v2ntyz6 66yrg8 vafter that, a second stone is thrown straight down with a 82v z66a vb(rynjtg6yn 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. Thfa f5.kqrhri fo:+:; qe 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 +r fqi5koq:a.hr; ff: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,-bhucrrp 68 g(,d)cea how long would it take a free-falling parachutist t ,pr b(ehc68gradc)u-o 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 perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers throuo3 lm byqkl)d ds mukp0sj lf3+c(e2+w; u0o.4gh a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast l2qdfsl kje0ob43 3. m+o uucml)ds0 pw+(;yk 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 Joeeyszzl 5zor7 5.bnp )7cn7fpwl- ad uqx,4 ,w6 can. How many times higher will Bill’s ball go than5xpnaub e,7)n rzds -lz5woc 7q6w7 p4.y,zlf Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the grou7msd g0-.nmze v82eo;vwq xx :nd 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 the ball and throws it up to you, sum:qdzvx2s; 0nmv w-xg .7eo8ech 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 tzmy uj:jb68urxj z(9)he 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 the 0.x )zb9(j8ruzy:j m ju63 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two biv.93l h 0yo.ck4fs*n(ncyu ycyuf5r 8cycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher averaguc8kf4n 3u. r l.*vnyyco 90hy 5(scfye velocity?