Does a car speedometer measuthund8. 3o:skdb(v9zb; dsz)re speed, velocity, or both?

Can an object have a varying speed if its vel.ff+3g98m9 wudu op o6jew4hw ocity is constant? If yes, give exa. ohed36 8o wupj9w m9ug4fw+fmples.

When an object moves wi iogiol 3zvk, dj fti:d3,:uu,3j 3g5rth constant velocity, does its average velocity during any time interval differ from its instantid3 do3:fi3 :,,tkujz3l,i gvjro5gu aneous velocity at any instant?

In drag racing, is it possibl zk5;:26 2mdb vkrgqs.a oxm+re for the car with the greatest speed crossing the finish li2x ravm :q2g5k k6o;rzm+b.d sne to lose the race? Explain.

If one object has a greater speed than a second object, df 1lf )t1ofrqpd08lo6oes the first necessarily have a greater acceleration? Explain, usingo8r)opffq16dfl10 lt examples.

Compare the acceleration of a motorcycle th6 83swjase g )dlxf1 +3jkajo*gt(5qpat accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest dws t3jl as5f8+k eg*ajjop x(q)3g61 to 10km/h in the same time.

Can an object have a no9*pfep/y ( 1 9jrox,iuq,iuh urthward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acce j/hj3 :clr*s-3he cnlleration is positive? What aboulcc-n s :/jjr3leh3*ht vice versa?

Give an example where both the velocity and acceleration are o12idc*+ta:g-f,e y9g eoyi v negative.

Two cars emerge side by side wulc43xc.k 4i 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? Expculk.4i4 3wcx lain your reasoning.

Can an object be increasing in speed as its accelerationos)qr h1 hnhv5i)a5c* -gm/yq decreases? If so, give an examp/rm5sc 5 gv-qn a*ihohy ))1hqle. If not, explain.

A baseball player hits a foul ball straight up into the air. It le;fxbxq; 43 q(evn,x dc 4.fcifaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when tdn v4,x;.cq(bf f iqxcx;fe43 he catcher catches it?

As a freely falling object speeds up, * fl7:q+s-uc xxvs)mr what is happening to its acceleration due to gravity — does it increase, decrease, or stasqxsfv um:c-*x+7l) r y the same?

How would you estimate the maximum height ol* eth4zp//5ltt/qy ob; 5 jryou could throw a ball vertically upward? Hoq y5o rpzebtlo//h* j/5t4;ltw would you estimate the maximum speed you could give it?

You travel from point A to p s(w n/fclt8/r *cjqg6oint B in a car moving at a constant speed of Then you travel the same distance fro(g6r sn8jc wlc*fqt/ /m point B to another point C, moving at a constant speed of 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-m3c; cqyrz)zn6 -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 sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tiq;cz)yz6 ncr3 ed so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rockum7 /8x tl,yqolowaq)dh2: 6h falling from a cliff, an elevator moving from the second floor to the fifth floor making stops alongllo/a2wd h x,)mt q7q68:ouyh the way, a dish resting on a table?

An object that is thrown vertically upward we2 i7d 7nzee2fill 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 acceleration due to air resistance is always in a direction oppos ene2eizf7d72ite to the motion.]

Can an object have zero velocity :diu ah7sw,l7a 4kz9fand nonzero acceleration at the same time? Give 7adlz,h9s4k7 fwu :aiexamples.

Can an object have zero acceleration and nonzero velocity at the same time? g;( lw vxf0,agGive wfgv( x 0ga,l;examples.

Describe in words the ml luinx 6-uv:dr: 3eycy6r0. votion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by vucyl:.l iy3x-6uv0:6nerrdwalking or moving your hand.]

Describe in words the motion of the object graphed in Fie2 y* r)ya6pnkz0vw 3lg. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25 h /y d7h r1t340taqtshw?    km/h

  A bird can fly 25 km/h How long does it take to f wm2x gp:5f(poly 15 km?    h

  If you are driving along a straight road and you look to thp/hal ,hz 5+nge side for 2.0 s, how far do np z +l/ghha,5you travel during this inattentive period?    m

  Convert 35 mi/h to 0zx gqy0nr/rkx286c f/03fq y9o bpwk
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frojfcnd, )x8 7utm $x_1$ = 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 steayjwo;x-qe0e 8dily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive ;y0qejo -8ewx 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 fivc5; y19bpm ipgk)fkq 2e seconds between a lightning flash and the following thunder gives the distaniqp2kbgf 9 )yk1;5pmcce to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a gtoi5paf+6 :1- gybul quarter-mile track in a total time of 12.5 miogp6 -a1t5l :yiu fg+bn. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away fzi2( t7 ylt8bd e66qabrom its trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and id62lbt(6e8tqbaz7 ygallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each has a speed of 95 6ewrb rz+yq9)2xt:wc km/h with respect to the ground. If they are initially 8.5 km apart, how lexqw9b t+2z:wyc 6 r)rong will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck +oi)af n* rbvd9+ec9 straveling How long will it take the car to r+* bsoev +fn)dci9ar9each the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encoun*b2 d,bjkcn6s ters a tailwind that boosts itskc2 *sbdjn,6b speed to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round-tnrvnv*zdk+ / cz yc8s4y 1z),xrip in which the outgoing 250 km is covered at 95 km/h + xn yc zsk/vn)z8z,4c *1yrdvfollowed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball travelcfs,en4o) ph ;tsq4,s+urk3 ling with constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitti t4k ssf,q 3),r;uhplcsone4+ng 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 from rest to r dmxdu(qj;r( f:5 xo595 km/h in 6.2 s. What is its average accelerati5jx5 :d(r x(m;odufq ron in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her ac4tg8 tcslzind486 b/ aceleration 8d 4ic 6gtsnazt4/lb 8
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an acceleration of abous jckx5 22b+vw hk2ole :pv.u0t kuek+hxb.p:wv0c 2o2js v2l5 $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s. If it then b qq5v:)5)w5e8mb jkfv . -jk wsencih:rakes and comes to a stop in 4.0 s, what is its acceleration in vq8c bjjmq ke5 ws i:n):.e5)f5 hvkw-$m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 and moves in a stgqn794 yym4l/wu2ta uraight line, is given as a function of time in the foll yqwu24l9ng y ta4/mu7owing Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 w2*yktk c+b.o m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constant acce2o*kkb y w+.ctleration.    $m/s^2$    m

  A car slows down from 23 m/s to re; pu9w7 l/sbbtfrx nf0:nl)*hst in a distance of 85 m. What was its acceleration, assumed c0tb lx)s7nl;b9f rp* nhu:fw/onstant?    $m/s^2$

  A light plane must reach a sp*emg( / ylvw-wt 6w/yueed of 33 m/s for takeoff. How long a runway is needed if the (constant) *wyyg -l( m//euwtvw6 acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed (ofz8s0kqu v35/b5hwdq 2 l;hcfl about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and hs5vb lwuhlfc;2d h50q 8 kq3z/ow 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+l,v- kmx s52npxmgofv 0t,+y rest in 6.00 s. How far did it tran -2fmv+ ,5txopklxgy +m,0v svel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway x(j1 :c,vygnn4fqrx q/9vw5v5o 4btw . Assuming a d5q9w t w /nxr v:14oc jy54,q(bxvfngveceleration 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 an8 fhrm,2s1idz ty0y2 gcc1 j8xd the driver comes to rest after traveling 0.80 m. What was the average accelyr s2dcmx1218zf0c h,gjiy8teration 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 txfgs+ j,8rpn78d6yob5v95lal t ,pv for a car with an initial speed of 95 km/h and human reaction time o5p7svly jxdn+g la88t 9tf6 rbp,o ,5vf 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance opyhb bl0k) 0t3f 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 hie60uk-q3bb+ubka5 m fi-hrwic+vwu/ h +8x 8yghway. The car’s driver looks for an opportuni+ fm+ /e+5u ucqx8i b -0buhvwyhk8a3irb6k-w ty to pass, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to completer;seqfhq+g( 5 nw*x;m the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner mus*q(r w5snxhqe g+fm;;t then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car a/n lou5uf u8+nu8z0so t 45 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 intersection (Fig. 2–31). Should /n n u8lu5+8ous0uzfoshe 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 lag glg/0 x6iirc0)y7 below after 3.25 s. How high isgxc0 yarig g06l)i7/ l the cliff?    m

  If a car rolls gently97bpd;a0/c vqhy 07k/ zeqr pc ($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

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

  A baseball is hit nearly straight up into the air withowlj4 6+w /v 2d()n ,eyxrcw4crn(pqp a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vertically upward. With wha+fy y (n0vgxvz/w-g0y t speed did he throw it, and what height did it f-+xyn 0g(vyzwgv0 y/reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under tj 2 so-6mm8;i2,;brdvakso st tl*my6he influence of gravity. Draw graphs of (a) its i-2sjmlm66sstdb ky rv; m at;2*o8 o,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 w bk3s9bpql n60 4en ;1gyyhi6hith a speed of 5.20 m/s. At a height of 125 m above the Earth, a package 3lek yg1064bn yh9;i6sbhpqnis dropped from a 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 frok i0p) dnk,.zim rest, show that the distance traveled during 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 ankdk,zi)pn.0 i d 2–21.

If air resistance is neglected, show (algebraically) that a:q 1lzm/midp) i.jtl, ball thrown vertically upward with a speil1tdm,.:jq/lpi) z m ed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward wi.jc pja/dk(a wadnmxat-(h*4.z 6i+ xth 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 in Fig. 2–18 (m9di;- *t ouklml,a+ vor number of photoflashes per second). Assume the apple is about 10 cm in diametek vm 9t -*iuoma,lld+;r. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 ,)0:oxmcfuvx s to travel past a window 2.2 m tall (Fig. 2–32). Fro0omucx x), f:vm what height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean ( umbsnux *.shwd 18k/gvjp,1is heard 3.2 s later. If the speed of sound is 340 m/s , how high is /1guwnpx m1bh 8j,suvk(*.ds the cliff? H =    m

  Suppose you adjust your gardenkp7i0v qtkeh9mtu:,ub ( + *jn 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 the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water skt0n(*ei9+uj7 : vkuqt,ph b mpeed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with .9em*v/k2 q mdd jk7k82e pvjwf c-d0ga speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fi djvd*kk .w/pqjed02kmg8f mv7-9ce 2g. 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 m above the stretcb a-f,t;w91 jfwcy8 et with a vertical speed of 13 m/s If the ball was thrown from the ;8ca-jt9wftc byf w1, 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 funcgqzc3c195 vlw0v9 hjo tion of time. (a) At what time was its velocity greatest? (b) Durinq9l 19gc jzwco0 h53vvg 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 functionp)a sar*f0uk8 of time is plotted in Fig. 2–28. What is its instantaneous veloca us80pr)*fakity
(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 automobmqn7wa l)-w g7ile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shiftawgl7 w)mn q-7ing 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 th3vrp;hwt e 7spf .0k/. jpd)tce previous Problem (Fig. 2–35) w )j p3.dwr7c0khp.sv/ ;ftt pehen 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 d,na8 ks tnesoc8 6ia;,uring
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t grag tcl;rlf. iqx0pnv:cx8*x46ph for the object whose displacement as a function of time is given by 8xl;x 4 rtgx:6*v 0cnqc.pfliFig. 2–28.

Figure 2–36 is a position versus time graph fo68o1qtskoj f +:aol60-qu kozr the motion of an object along the x aqfoosajz 6u k-1tl: o6o08qk+xis. 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.

  A person jumps from a fourth-story window 15.0 m above a firefighter’sqreu+ oha *y;9 safety net eh;u9q+ry* oa. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sixth what it.(9 gq(fc nxss 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 same initial velocit. (c( 9qxsnfsgy?

  A person who is properly qa(z duk8b;o+qed38q constrained by an over-the-shoulder seat belt has a good chance of surviving a car collisd8 a;dq(e3zqu ok8b q+ion if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above t tb-aq4j0r7iyhe 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 down from the britq7 b ayir-0j4dge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufaiw9 5gub u9o47j (nz vsx2im3mcturer tested its cars for front-end collisions by hauling them up on a crane and dropping them from a cers 4i(j o539mbvxi7uwmn92zug tain 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 Earth277 : 8 rj: meqszn;pns 2iwjmg2rqwx. travels 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 acceleratio :1d7.jzcnod hn 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 speed of the last zn :hd7.oj dc1car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m abo1a.m is6;ig yvgv s8-ove the water’s surface into a deep pool. The simsgv8ig1;a- . oy6v person’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 sysvqj inw2 dig5w( *r88(op w9zwtem, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.98(wwo(i n2d w8vgip r*5zqjw0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight 2t: c3/ywadjidown 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? Assumctyw 2 ijda/:3e the fish is at the surface of the water.    m

  In putting, the force with which a0 0wdmj.y f,zue74dc+y e0po h golfer strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m lod pe+u0yey,j7mz 0.dh40ow cf ng 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 see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at a constant spegxx7olqud,.rw x/ux(d6xu8l6 xl-q 4ed of 6.0 m/s Jwod 6 -x.ulruq7xqxd lx,(xxg/6 48l uust 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 of a high building. A sejn*viu 2omv: 6cond stone is dropped 1.50 s later. How far apart are the stones when t:u m6*j2ivonvhe 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 of6qjem :xx4h al2-wq, z a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must b qq-x,ewa:4jl xz mh62e maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at h.7qrvca (2xe7:nq lv 18 km/h . At the bottom, 4.0 km farther, his speed isr(h: c qven.x la27v7q 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.daq ,5ebd)fwgdmhq:k c4 s*)( The first child can bounce up one-and-a-half times higher than the secondd(d))qwedksm4qfh:* 5c, agb 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 a 1.10 g;l vvk(w.u)*7 upbpq-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 .guv)kqb uv; *p(plw7Fig. 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 Idu tbto(qm2wn2h ;xr.8nh e1 h+5a7dqn 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 releasth.n wd+ q(odher2 ;nux52t8ah71qb med (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertigtnlk 3 xca-n47um(1rcally, 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 intersection has a jdbn0lly 8*)otb(u m,*oe sf(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 firstl)*mbo, ns d8b j( u*fe(t0loy 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, yi66w( ruhdo1passed by a speeder traveling at a constant 120 km/h takes oy61 6uh( irwdoff in hot pursuit. The 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 buildinlk59s w/p5-tfx vl) kmg; 2.00 s after that, a second stone is thrown stk-5pw v)/x9lkfl s5mtraight down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time.) 88*lqj9io h0ejcykx The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a)*9 8ey xhij0o8 ljqkc building and hits the ground 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 parachutixh7mjp w5 x n+u/1on8zst to fall from a m1po8 n7w+zn/xxh uj5plane 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 burgerrf ue 7d gqchr379ar+6s 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 fd7r3a7egqrruc6 9+h 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 t dsr44 rzg1tl2 c/ko4bimes faster than Joe can. How many ti2r bs4gt4d l4 okcrz/1mes higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your p6(4p ffjxjq1 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 picks up the ball and throws it up to you, such that pj6 x1jfp(q4fit 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 particularf *fcq tpc;jc/5)68 oyhv7i. v5shgq o 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 0.3 s make for the estimates of the building’s h/7qfv fvqh o5hti y 6jg5*8c sc)o;.pceight?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A jb.)a bgi g: wk4wx55dand 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 aj55bxg iwdw: bg a.k4)verage velocity?