In what ways is the word “work” l*it jkm1)f tc:rg+5, ygtm a. mg7k5mas used in everyday language the same as that defined in physics? In what ways is it different? Give examplestt im,m tm7:grcgfjg5)ykk*+m5a.l1 of both.

Can a centripetal force ever do workj9/hornru: l)rgt;v :, xsv s8 on an object? Explain.

Can the normal force on an object ever do w,t:qol5x 5a vd: 5 bjb*ud(ukuork? Explain.

A woman swimming upstream is not moving with respedm*(,1( teav ;le0movgt9i nqct to the shore. Is she doing any work? If she stops swimming and merely fload*0mvit emvqa leg,9(1;(tnots, is work done on her?

Is the work done by kinetic friction forg5rl+oq336d b8 xjaxpces always negative? [Hint: Consider what happens to the dishes when you pull a tablecloth out from under xqbagjro38p5+l63dx them.]

Why is it tiring to push hapj2*lup**hrgjzj/a57p- zk g rd against a solid wall even though you are doing no work?j5a*2zpu/ pjr-ghp *z l*7jgk

You have two springs that are identical except that nr.o 77wv 0n loat-kg.spring l is stiffer than spring 2 l7. go.7 - ktanw0novr$(k_1>k_2).$ On which spring
is more work done $(a)$ if they are stretched using the same force, $(b)$ if they are stretched the same distance?

A hand exerts a constant horizontac eswqovdk;)6gc221 zl force on a block that is free to slide on a frictionless surface (Figg261kovqcc2 ews;)dz .6-30). The block starts from rest at þoint A, and by the time it has traveled a distance $d$ to point B it is traveling withe bint $o$ point B it is traveling with speed $\nu_\mathrm{B}$.When the block has traveled another distance $d$ to point C, will its speed be greater than, less than, or equal to 2$\nu_\mathrm{B}$? Explain your reasoning

By approximately how much does yi8eb gmzk.nxccsi a:2 rk,f 4m0;d)6 dour gravitational potential energy change when you jump as hi dbm)6m;x8i2s4feari k,.cc: dzngk0gh as you can?

In Fig. 6–31, water balloons are tossed from the roof of a builgj5wx c(w/zo 5fgm,tt v1,p/h ding, all with the same speed but with differtg15x/omzh(/gp wc , w f5t,jvent launch angles. Which one has the highest speed on impact? Ignore air resistance.

A pendulum is launched from a point that is a height h abovy/ 8 x1bz9jlj,cfd a;ke its lowest point in two different ways (Fig. 6–32). During both launches, the pendulum is given an initial speed of 3.0m/s On the first launch, the initial velocity of the pendulum iskx8z /1fy;l jb,cda9 j directed upward along the trajectory, and on the second launch it is directed downward along the trajectory. Which launch will cause it to swing the largest angle from the equilibrium position? Explain.

A coil spring of mass m rests upright on a table. If you compress the spring byn+ 3opp13amh b;qmt5 h pressing down with your hand and then release it, can thm; 3tbpomh3 an1h5pq+ e spring leave the table? Explain, using the law of conservation of energy.

A bowling ball is hung from the ceiling by a steel wire (Fig.ahw*d :35 wh2buhf k2u 6–33). The instructor pulls the ball back and stands against the wall with the ball against his nose. To a3 k d h*hwhua52wbf:u2void injury the instructor is supposed to release the ball without pushing it. Why?

What happens to the gravitational potential en-r- 9v: ueasln (:haqoergy when water at the top of a waterfall falls to the pool u:l(a nh e9aos-q r-:vbelow?

Describe the energy transformations when a child hops around on a pogo stij,f- atd00eg3-v nxshck.

Describe the energy transfor:3uh8e ca0x momations that take place when a skier starts skiing down a hill, but after a time is brought to rest by acheu08 o:m3xstriking a snowdrift.

A child on a sled (total mass m) starts from rest at themwz5*kk* hapzy0 xt,(jyiw ;qoz6:c8x *oj7l top of a hill of height h and slides down. Does the velocity at the bottom depend on the angle of the hill if (a) it is05j ;pz(z:*6w aoy8ymx*kticq, jh *7oxklwz icy and there is no friction, and (b) there is friction (deep snow)?

Seasoned hikers prefer to step over a fallen log in theuh,i)l.aa e31yhlvhqg/38 wn ir path rather than stepping on top and jumqlwn 3e3/ .1 a)vh8 ,hhugylaiping down on the other side. Explain.

Two identical arrows, one with twice th 5h:xpgzy - fdq+ 35e.p1mqrqec q*9jde speed of the other, are fired into a bale of hay. Assuming the hay exerts a constant frictional force on the arrows, the faster arrow will penetrate p*my:hd q .9r3 q15xg5cpzqjdfq+ e e-how much farther than the slower arrow? Explain.

Analyze the motion of a simple swinging pendulum in terms of energy, (a) ignora 2 tfafus364zing friction, and (b) taking friction into account. Explai aat f3sf6uz24n why a grandfather clock has to be wound up.

When a “superball” is dropped, can it rebound to a height gt7fyatht57t6s. s 3zc vjsd 7;reater than its original height? Expltf7hsss 7jy.7tt3va6 d t;5 czain.

Suppose you lift a suitcase from the floor to a table. The work you do kirm oto6o:7ea-l1q) k*5n raon the suitcase depends on which of the following: (a) whether you lift it straight up or along a more complicated path, (b) the time it takes, ( o6rakik-r 751 tma)*eql noo:c) the height of the table, and (d) the weight of the suitcase?

Repeat Question 22 for the pow92awqzcip5mgpxue63j7 u(6b ;2 vdrm er needed rather than the work.

Why is it easier to climb a mountain via a zigzag trail than to clic . t6oud7s y0j+pn7tzmb straight upzdu0 7t t+7.s nyoj6cp?

Recall from Chapter 4, Example 4–14, that you can use a pulley and ropes to dec2*,vt vyvmym(rease the force needv 2yy*(,m vmvted to raise a heavy load (see Fig. 6–34). But for every meter the load is raised, how much rope must be pulled up? Account for this, using energy concepts.

  How much work is done 7u8n;yp9p n (cs4iszaby the gravitational force when a 265-kg pile driver falls 2.80 mn84zc;py7sip n s( ua9?    J

  A 65.0-kg firefighter climbs afu)z3f x2/)9hd4jlpk: k meyua3z o 1z flight of stairs 20.0 m high. How much work is requirl39 zj:m)/f3fk42ux 1e ua)z yophd kzed?    J

  A 1300-N crate rests on the floor. Hoo*sc-d-uv ze, w much work is required to move it at constant speed (a) 4.0 m alonso ,vedzu-* -cg the floor against a friction force of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (horizontally) pushing apflr:xpuxh.w 2,( 1is lmdg,+ 160-kg crate 10.3 m across a rough floor without accelerati m:fg.+xhsxl pl(r ui,12,pwd on, if the effective coefficient of friction was 0.50?    J

  A box of mass 5.0 kg is acceleratetefjw;8 8vdh1d by a force across a floor at a rate of for 7.0 s. Find the net work done on the bo1hf8w;d ve8j tx.   J

  Eight books, each 4.3 cm thick with mass 1.7 kg, lie flatm9wh4*u0r+i e sceru* on a table. How much work is required to stack the ruwe*04re+9smih *ucm one on top of another?    J

A lever such as that shown in Fig. 6-35 can be usn3o0(lb ;akt hed to liff objects we might not otherwise be able to liff. Show that the ratio tba (0o; nhkl3of output force, $F_{\mathrm{O}}$, to input force, $F_{\mathrm{I}}$, is related to the lengths $\iota_\mathrm{I}$ and $\iota_\mathrm{o}$ from the pivot point by $F_{\mathrm{O}}/F_{\mathrm{I}}=l_{\mathrm{I}}/l_{\mathrm{O}}$ (ignoring friction and the mass of the lever), given that the work output equals work input.

  A 330-kg piano slides 3.6 m down a 28° .ge pnut6/5bo v2s2flincline and is kept from accelerating by a man who is pushing bvgot bf22 spl5.e6nu/ ack on it parallel to the incline (Fig. 6-36). The effective coefficient of kinetic friction is 0.40. Calculate:
(a) the force exerted by the man,    N
$(b)$ the work done by the man on the piano,    J
$(c)$ the work done by the friction force,   J
$(d)$ the work done by the force of gravity,   J
$(e)$ the net work done on the piano   J

  (a) Find the force required to give a helicopter of mass M an acceleration of 0.*tpxgy1tf 1b 910 g upwardtbg9p1t*fyx1 .    Mg
(b) Find the work done by this force as the helicopter moves a distance h upward.    Mgh

  $\text{What is the minimum work needed to push a 950-kg car 810 m up along a 9.0$^{\circ} $ incline? }$$(a)\text{ Ignore friction. }$    J
$(b)\\\text{Assume the effective coefficient of friction retarding the car is }0.25.$    J

  In Fig. 6-6a, assume thke/ qa2i d)ch40vs8y ae distance axis is linear and that $d_{\mathrm{A}}=10.0$ m and $d_{\mathrm{B}}=35.0$m. Estimate the work
done by force $F$ in moving a 2.80-kg object from $d_\mathrm{A}$ to $d_\mathrm{B}$   J

  The force on an object, ac a w-9vrcg-pgs8 o65rcting along the x axis, varies as shown in Fig. 6–37. Determine the work done by this force to ps95-8ocg- wva cr6rg move the object (a) from x=0 m to x = 10 m    J
(b) from x = 0 m to x = 15 m    J

  A spring has $k=88$ N/m. Use a graph to determine the work needed to stretch it from $x=3.8$ cm to
$x=5.8$cm, where $x$ is the displacement from its unstretched length    J

  The net force exerted o3dys:o y)7btb ,wa5 d .twk0spn a particle acts in the $+x$ direction. Its magnitude increases linearly from zero at
$x=0$, to 24.0 N at $x=3.0$ m. It remains constant at 24.0 N from $x=3.0$ m and then decreases
linearly to zero at $x=13.0$m. Determine the work done to move the particle from $x=0$ to $x=13.0$ m
graphically by determining the area under the $F_x$ vs. $x$ graph    J

  At room temperature, an oxygen molecule, with m hut9 8(hahq288hywq18io fuoass of $5.31\times10^{-26}$typically has a KE of about$6.12\times10^{-21}$ J .How fast is the molecule moving?    m/s

  (a) If the KE of an arrow is doubled, by what factor has its speed increasedww4rpcygka0 :fkiv)j- 0/m g6? $ \sqrt{a}$ a =    (b) If its speed is doubled, by what factor does its KE increase?   

  How much work is required to stop aku9tmfz9 95(ol8 w.( kkqiwfc n electron $\left(m=9.11\times10^{-31}\mathrm{~kg}\right)$ which is moving with a speed of$1. 90\times 10^{6}\mathbf{m/ s}$ ? $\boxed{a\times10^{b} \mathrm{J}}$ a =    b =   

  How much work must be done to stop a 1250-kgcar traveling at 1x djf1nj77z 349 -xh uanrt)ci05km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whose string exerts an average force of 110 Nzou pjjl +t 6lv 4s+-/iedvq7, on the arrow over a distance of 78 cm. What is the speed of the arrow as it l4iv-vsqp zled ++ ljtoj,/u76eaves the bow?    m/s

  A baseball (m=140kg) traveling 32m/s moves a fielder’s glove backward 25 cm whentwsi/4k/6l5xu r -az u/b0l ma the ball is caught. What was the average force exerkt5 am sa uz-u /06xw/4l/rlbited by the ball on the glove?    N

If the speed of a car is increased by 50%, by what facebp q t/km8 8y:l*z4iytor will its minimum braking distance be increased, assuming all else is the same? 4mtk8ez y 8 *ib:yl/qpIgnore the driver’s reaction time.

  At an accident scene on a level road, investigators measurevs48) g +yczym a car’s skid mark to be 8gc +)vs8z my4y8 m long. The accident occurred on a rainy day, and the coefficient of kinetic friction was estimated to be 0.42. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes. (Why does the car’s mass not matter?)    m/s

  A softball having a mass of 0.25 kg is pitched at By thwt)x,altf )fp4,ivzbq9/ 3- aboh,l ne time it reaches the plate, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resistance during a pitch, if the dif atvol,t,a h3)/bxizqp,-f bwln4)9 stance between the plate and the pitcher is about 15 m.    N

  How high will a 1.85-kg rock go if thrown straight up by someone who does 80.9a eic,6(d/if6atrjekq5w-q o ,( dkw0 J of work on it? Neglect air re,ea j(dr(w i6,fwe da6kokti c5 -q/q9sistance.    m

  A 285-kg load is lifted 22.0 m vertically with an acceleratio,6-l wwsqd kq*n by a single cable. Determine,w*k6dsq w -lq
(a) the tension in the cable,    N
(b) the net work done on the load,    J
(c) the work done by the cable on the load,    J
(d) the work done by gravity on the load,    J
(e) the final speed of the load assuming it started from rest.    m/s

  A spring has a sprinw8,ycr: 2uqetg stiffness constant, k, of 440N/m How much must this spring be stretched to store 25 J ofq:yutw, 2ce8r potential energy?    m

  A 7.0-kg monkey swings from one branch to another 1.2+( qdx1dyhd4gq bu.+izyb7r*sp hy41 m higher. What is the change in potent+yq yhi rgd7.pu4dd zqb4 s+(1*xhb1yial energy?    J

  By how much does the gravi./yej 4 3fjxxftational potential energy of a 64-kg pole vaulter change if his center4/ jjf3.x yfex of mass rises about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizontal surface has8 7 h xymtdb-gw3/ei,b speed v = 65 km/h when it strikes a horizontal coiled spring and is bro3dw 7tebhi,x/bgy m-8 ught to rest in a distance of 2.2 m. What is the spring stiffness constant of the spring?    N/m

  A 1.60-m tall person lifts a 2.10-kg book from the ground so it is 0d 422fpmcrlab4l n 99a-mniccgv5 -b 2.20 m above the ground. What is the potential enecnb2- 9b-lpfrd40 aagc24c 9 n5vm mlirgy of the book relative to
(a) the ground,    J
(b) the top of the person’s head?    J
(c) How is the work done by the person related to the answers in parts (a) and (b)?    J

  A 55-kg hiker starts z9pvs5(+d5fpe fbw.iat an elevation of 1600 m and climbs to the top of a 3300-m . v5bzde5f sp+ ipw(f9peak.
(a) What is the hiker’s change in potential energy?    J
(b) What is the minimum work required of the hiker?    J
(c) Can the actual work done be more than this? Explain why. ----待选择----yesno 

  A spring with k = 53N/m hangs vertically next to a ruler. The end of the spring f78 u ++kr tko zgjt*.td8:nzfis next to the 15-cm mark on the ruler. If a 2.5-kg mass is now attached to the end of the spring, where will tzff:kkdgj.8u++ zn87t*tr othe end of the spring line up with the ruler marks?    cm

  Jane, looking for Tarzan, is running at top speed (5.3m/s) and grabs a vine hangf8o6)g m5uv 8.8zlfrgoc pob 6ing vertically from a tallf5u)fo.6l8v corogm gzb p886 tree in the jungle. How high can she swing upward?    m
Does the length of the vine affect your answer? ----待选择----yesno 

  A novice skier, startin (i:qn:wa4j8fl e2hbxg from rest, slides down a frictionless 35.0$^{\circ}$ incline whose vertical height is 185 m. How fast is she going when she reaches the bottom?    m/s

  A sled is initially given a shove up a frictionless ujz2fu mfst cd8(e:, p**cwt -28.0$^{\circ}$ incline. It reaches a maximum vertical height 1.35 m higher than where it started. What was its initial speed?    m/s

  In the high jump, Fran’s kinetic energy is transformed into gravitationar .4vbz1q/zrh 2y7t q3zr, 6wjho, xx:jy+pvxl potential energy without the aid of a pole. With what minimum speed must Fran leave the ground in order to lift her center of mass 2rb4zvjrwh jz1+2t:6 y3vq p,qx yxhr .o,/z7 x.10 m and cross the bar with a speed of 0.7m/s.    m/s

  A 65-kg trampoline artist jumps vertically upward from the top of a plj.xd*; ynt lo:atform with a speed of 5.0 m/s. oy .nljd:;xt *($\alpha)$ How fast is he going as he lands on the trampoline, 3.0 m below (Fig. 6-38)?$v_2$ $\approx$    m/s
(b) If the trampoline behaves like a spring with spring stiffness constant 6.2×10$^{4}$ N/m , how far does he depress it? $y_3$ =    m

  $\text{A projectile is fired at an upward angle of 45.0o from the top of a 265-m cliff with a speed of 185m/s. What will}\\\text{be its speed when it strikes the ground below?(Use conservation of energy.)}$    m/s

  A vertical spring (ignore its mass), whose spring stiffness constant isrevdqd-1 z9r t5x3.1q wi pv2w 950N/m is attached to a table 3prtw 1z-x9vw1 dv5.rqid2eqand is compressed down 0.150 m. (a) What upward speed can it give to a 0.30-kg ball when released?    m/s
(b) How high above its original position (spring compressed) will the ball fly?    m

  A block of mass m slides without friction along t h(j0zn:r spc3swl6f1 he looped track shown in Fig. 6–39. If the block is to remain on0sp flwz(1:srj n3hc6 the track, even at the top of the circle (whose radius is r), from what minimum height h must it be released?    r

A block of mass m is atquju 907qdq 5ctached to the end of a spring (spring stiffness constant k), Fig. 6–40. The block is given an iqu 7u5 qqc0d9jnitial displacement $x_0$ after which it oscillates back and forth. Write a formula for the total mechanical energy (ignore friction and the mass of the spring) in terms of $x_0$ position x, and speed

  A 62-kg bungee jumper jumps from a bridge. She is tied to a j9e/tm cisv,3) 3agnsg/rv n0bungee cord whose unstretched length is 12 m, and falls a total of 31 m. (a)ejv 3/gv 30trg )c/ssa 9nm,in Calculate the spring stiffness constant k of the bungee cord, assuming Hooke’s law applies. $\approx$    N/m
(b) Calculate the maximum acceleration she experiences. $\approx$   m/$s^2$

  The roller-coaster car shown in(mx;:k2ngx, 9a riwowe yb6(b Fig. 6–41 is dragged up to point 1 where it is released from rest. Assuming no friction, calculan(bx;abx2: w 6kr(mewg9yo i,te the speed at points
2    m/s
3    m/s
4    m/s

  A 0.40-kg ball is th lxk v)i nn5grv9:jj71rown with a speed of 12 m/s at an angle of 33 $^{\circ} $. (a) What is its speed at its highest point    m/s
(b) how high does it go? (Use conservation of energy, and ignore air resistance.)   m

An engineer is designing a spring to be placed at the bottom of an elevator sh(*tkiqhj dbjaw o;01+aft. If the elevator cable should break when the elevator is at a height h above the top of the spring, calculate the value tikh;+ wd* (aq10bj jothat the spring stiffness constant k should have so that passengers undergo an acceleration of no more than 5.0 g when brought to rest. Let M be the total mass of the elevator and passengers.

  A cyclist intends to cpkpdqt /km*-zr 2 (g+mycle up a 7.8 $^{\circ} $ hill whose vertical height is 150 m. Assuming the mass of bicycle plus cyclist is 75 kg,
(a) calculate how much work must be done against gravity.    J
(b) If each complete revolution of the pedals moves the bike 5.1 m along its path, calculate the average force that must be exerted on the pedals tangent to their circular path. Neglect work done by friction and other losses. The pedals turn in a circle of diameter 36 cm.    N

  Two railroad cars, each of mass 7650 kg and traveling 95km/h in opposiguzn:;/3 hsp p5 z;fwgte directions, collide head-on and come to rest. gz :pu5p;wh3gs n; fz/How much thermal energy is produced in this collision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slide 3.5 m high and reaches the bcx65iekj(sg-.6y b dcottom with a speed of 2.56c isyxd(jc. k -gbe62m/s How much thermal energy due to friction was generated in this process?    J

  A ski starts from rest and slides down a 22ety7k:c (h+k f $^{\circ} $ incline 75 m long.
(a) If the coefficient of friction is 0.090, what is the ski’s speed at the base of the incline? $\approx$    m/s
(b) If the snow is level at the foot of the incline and has the same coefficient of friction, how far will the ski travel along the level? Use energy methods.$\approx$    m

  A 145-g baseball is droppedznpt-,rg 6n9:2ap fzl from a tree 13.0 m above the ground.
(a) With what speed would it hit the ground if air resistance could be ignored?    m/s
(b) If it actually hits the ground with a speed of 8m/s what is the average force of air resistance exerted on it?    N

  You drop a ball from a height of 2.0 m, and it bounces back to a height p.1e c epk;q2gof 1.5 m. .c;2gpkpe q1e
(a) What fraction of its initial energy is lost during the bounce?    %
(b) What is the ball’s speed just as it leaves the ground after the bounce?    m/s
(c) Where did the energy go?

  A 110-kg crate, starting from rest, is pulled across a floor with a constant )u* b0jk8u*b*saxs j jhorizontal force of 350 N. For the first 15 m the floor is frictionless, and for the next 15 m the coefficient of fr)uj sj*x8as* j*bk0 ubiction is 0.30. What is the final speed of the crate?    m/s

  Suppose the roller coaster in Fig. 6–41 passes point 1 with a i: a6p +) +jntpqbqc,fqi+pb*speed of If the average force of friction is equal to one-fifth of its weight, with what speed will it reach point 2? The distanceb+p p * + q,:)iq6+ijbnaqcpft traveled is 45.0 m. $\approx$    m/s

  A skier traveling 12m/s reaches t e;d1ky;gv-q thq4(t rhe foot of a steady upward 18.0 $^{\circ} $ incline and glides 12.2 m up along this slope before coming to rest. What was the average coefficient of friction?   

  A 0.620-kg wood block is fi5z4pni *l yew1qy5;w hrmly attached to a very light horizontal spring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compressed 5.0 cm and released, stretches out 2.3 cm beyond the equilibrium position before stopping and turning back. What is the coefficient of kinetic frwhny 5w*5ei;4y 1p qlziction between the block and the table?   

  A 280-g wood block is firmly attached to a very light horizontal spru w,uhy5 qdz5:s-36bo3m puxvb r1)/muf0j jking, Fig. 6–40. The block can slide along a table where the coefficient of friction is 0.30. A force of 22 N compresses the spring 18 cm. If the spring is released from this position, how far beyop,k 5 5m-uj mf1sjh)rq 0 ubw3zo/b6xy:vduu 3nd its equilibrium position will it stretch on its first swing?    m

  Early test flights for the space sh)530nbz-a + zumyblvhuttle used a “glider” (mass of 980 kg including pilot) that was launched horizontally at 500km/h from a height of 3500 m. The glider eventzu0 b3-a)z+myvb5 lnhually landed at a speed of 200km/h (a) What would its landing speed have been in the absence of air resistance?$\approx$    km/h
(b) What was the average force of air resistance exerted on it if it came in at a constant glide of 10 $^{\circ} $ to the Earth?$\approx$    N

  How long will it take a 1750-W moxf z x35u:xkloq3s.x (tor to lift a 315-kg piano to a sixth-story window 16.0 m aqx3. s3x xozu5f:(x lkbove?    s

  If a car generates 18 hp when traveling at a steady 88km/h8wap fhjo b f.m3tpjg 5h-.7x1 what must be the average force exerted on the car due to friction and jom5afw8tpfp h.31-b7jx hg. air resistance?    N

  A 1400-kg sports car accelerates from rest to 95km/h in 7.4 f0:xj ,i.d*gqt)wvdkdu(7pn s. What is the average power delivered d f)ptj,v.i kwdg7 x0* und(q:by the engine?$\approx$    hp

  (a) Show that one British 81wb 0bd neqm*9u-yvq2jm eh0horsepower$ \mathrm{ft}\cdot\mathrm{lb/s}$ is equal to 746 W.
(b) What is the horsepower rating of a 75-W light bulb?    hp

  Electric energy units are often expressed in the form of nlxgr .42f+8s. cn .zp u-jybf“kilowatt-hours.”
(a) Show that one kilowatt-hour (kWh) is equal to $3.6\times10^6$J
(b) If a typical family of four uses electric energy at an average rate of 520 W, how many kWh would their electric bill be for one month $\approx$   kW*h
(c) how many joules would this be?$a\times10^b$ J a =    b =   
(d) At a cost of 0.12 dollars per kWh, what would their monthly bill be in dollars? Does the monthly bill depend on the rate at which they use the electric energy?    dollars

  A driver notices that her 1150-kg car slows down from to 651bn.wb(t p;d bkm/h in about 6.0 s on the level when it is in neutral. Approximately what power (watts and hp) is neede;1 (wbtpnb.dbd to keep the car traveling at a constant 75km/h.    hp

  How much work can a 3.0-hp mo3qxd (+5qgts t* 4thwgtor do in 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates a :xt4vu igzgw*uj (df dow ,*:oc2d *m17.3-kg shot from rest to 14m/s If this motion takes 1.(2ovf d jxcgw4,wg* d::m otuuz*di*15 s, what average power was developed?$\approx$    W

  A pump is to lift 18.0 kg of water per minute through a ; iqvi/h c0 80znwf.ccgdh .o7height of 3.60 m. What output raticiz.h /nc 8if 0ovqhwc0g.d7 ;ng (watts) should the pump motor have?    W

  During a workout, the football players amg :*en9bx/yyka6 ju 8t State U. ran up the stadium stairs in 66 s. The stairs are 140 m long*g nbu9x/6am8 k ejy:y and inclined at an angle of 32 $^{\circ} $. If a typical player has a mass of 95 kg, estimate the average power output on the way up. Ignore friction and air resistance.    W

  How fast must a cyclisao. :h(69;py6ddnhchh 2t c wp58oeqrt climb a 6.0 $^{\circ} $ hill to maintain a power output of 0.25 hp? Neglect work done by friction, and assume the mass of cyclist plus bicycle is 68 kg.   m/s

  A 1200-kg car has a maximum power vf.grdnqgj .(m n)0du3 ac.8 aoutput of 120 hp. How steep a hill can it climb at a constant speed of 75km/h if the frictional forces add up jangqcv)n3m.d.ud ag rf 80 .(to 650 N?    $^{\circ} $

  What minimum horsepower must a motor have to be able to dr -g;03kon nbpu2t3f ktu y)cy)ag a 310-kg box along a level floor at a speetuukn;y fpko n) -cg)32tb0y3d of 1.2m/s if the coefficient of friction is 0.45?    hp

  A bicyclist coasts down a 7.0 id93f bmm/ lv7zjx.z3 $^{\circ} $ hill at a steady speed of 5m/s Assuming a total mass of 75 kg (bicycle plus rider), what must be the cyclist’s power output to climb the same hill at the same speed?    W

  Designers of today’s cars have b8 jfyn3o 9qyl f0(np k(5+zk(tapj1myuilt “5mi/h(8km/h) bumpers” that are designed to compress and rebound elastically without any physical damage at speeds below 8km/h If th p(t(l5j0pqnf3 zkyjky1omy 8(a+nf 9 e material of the bumpers permanently deforms after a compression of 1.5 cm, but remains like an elastic spring up to that point, what must the effective spring stiffness constant of the bumper be, assuming the car has a mass of 1300 kg and is tested by ramming into a solid wall? $a\times10^b$ N/m a =    b =   

  In a certain library the first shelf is 10.0 cm off the j(0f4flg8 0jv emeic.v edr()ground, and the remaining four shelves are each spaced 30.0 cm above the previous one. If the average book has a mass of 1.5 kg with a height of 21 cm, and an average shelf holds 25 books, how much work isjm)ejgvifdr (el08 (.v0e4fc required to fill all the shelves, assuming the books are all laying flat on the floor to start? $\approx$    J

  A film of Jesse Owens’s famous long jumr,0tme;de6 4+i1n gzrh 2kcbmp (Fig. 6–42) in the 1936 Olympics shows that his center of mass rose 1.1 m from launch point to the top of the arc. What minimum sm 0g6db1 z,e;r ec+tinkm42r hpeed did he need at launch if he was traveling at 6.5m/s at the top of the arc?   m/s

  The block of mass m sliding without friction along the looped track shown in Ffq1,pwa4vg a )igv,aaqf p)1g4w . 6–39 is to remain on the track at all times, even at the very top of the loop of radius r.
(a) In terms of the given quantities, determine the minimum release height h (as in Problem 40). Next, if the actual release height is 2h, calculate    r
(b) the normal force exerted by the track at the bottom of the loop,    mg
(c) the normal force exerted by the track at the top of the loop,   mg
(d) the normal force exerted by the track after the block exits the loop onto the flat section.   mg

  An airplane pilot fell 370 v(z 1p8 *oz-)eghefvz m after jumping from an aircraft without his parachute opening. He landed in a snowbank, creating a crater 1.1 m deep, but survived with only minor injuries. Assuming the pilot’s mass was 78 kg and his terminal velocity was 3 pe*ghf81zozv -e vz()5m/s estimate
(a) the work done by the snow in bringing him to rest; $\approx$    J
(b) the average force exerted on him by the snow to stop him;$\approx$    N
(c) the work done on him by air resistance as he fell.$\approx$    J

A ball is attached to a horizontal cord of length L whose other end immoql.q -i*6)ho yib+s fixed (Fig. 6–43).miyo.*qlhmq 6b oi+-)
(a) If the ball is released, what will be its speed at the lowest point of its path?
(b) A peg is located a distance h directly below the point of attachment of the cord. If h=0.8L what will be the speed of the ball when it reaches the top of its circular path about the peg?

  A 65-kg hiker climbs to the top of a 3700-m-high mountain. The climb is m ( v.h1gjtatx7ade in 5.0 h starting at an elevation of 23ag hj 17tt(xv.00 m. Calculate
(a) the work done by the hiker against gravity,   
(b) the average power output in watts and in horsepower,   W    hp
(c) assuming the body is 15% efficient, what rate of energy input was required.    hp

  An elevator cable breaks when a 92game3kt o0ba. d mxw 317n54cr0-kg elevator is 28 m above a huge spring ($k=2.2\times10^{5} \mathrm{N/m}$) at the bottom of the shaft. Calculate
(a) the work done by gravity on the elevator before it hits the spring,$\approx$    j
(b) the speed of the elevator just before striking the spring,$\approx$    m/s
(c) the amount the spring compresses (note that work is done by both the spring and gravity in this part).    m

  Squaw Valley ski area in Cgnv+(0u a8m. 5fqrc b hj/d4rlalifornia claims that its lifts can move 47,000 people per hour. If t qr(8af0ngb lhu.5+rv/jdcm 4he average lift carries people about 200 m (vertically) higher, estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam at the rate of 650kyovs vcj mk1x1h 7w d/ lzht0h6)mh.06g/s and falls vertically 81 m before strik)7sm.1tc dv wkvly 0/6oh mjhh1 0z6hxing the turbine blades. Calculate
(a) the speed of the water just before striking the turbine blades (neglect air resistance), $\approx$    m/s
(b) the rate at which mechanical energy is transferred to the turbine blades, assuming 58% efficiency.    W

  Show that on a roller coaster with a circular vertical loop (Fig. (6r u(fecs6tw6;iysf +aue(0qvu/ kjvwcs )96–44), the difference in your apparent wei ufewy)utvc6 (w aju;k(e9s cs/(6 ir+ f6vs0qght at the top of the circular loop and the bottom of the circular loop is 6 g’s — that is, six times your weight. Ignore friction. Show also that as long as your speed is above the minimum needed, this answer doesn’t depend on the size of the loop or how fast you go through it.    mg

  (a) If the human body could convert a cando: m 4x b;nz4rceu9k/cy bar directly into work, how high could an 82-kg man climb a ladder if he were fueledn ruzcbc4;ox4k 9/m: e by one bar (=1000kJ)    m
(b) If the man then jumped off the ladder, what will be his speed when he reaches the bottom?    m/s

  A projectile is fired at an418fhh8.btuzipa,rar q 9:fx upward angle of 45.0$^{\circ} $ from the top of a 165-m cliff with a speed of 175m/s What will be its speed when it strikes the ground below? (Use conservation of energy and neglect air resistance.)    m/s

  If you stand on a bathroom scale, the spring inside the scale compresses;)+ 0 y1wajqkiis km,9z.q yen 0.60 mm, and it tells you your weight yij emiw,1q a;)9ky n.+0 skzqis 710 N. Now if you jump on the scale from a height of 1.0 m, what does the scale read at its peak?    N

  A 65-kg student runs eo(qldbon7*y4:gd : wat 5m/s grabs a rope, and swings out over a lake (Fig. 6–45). He releases the rope when his velocity is zdobo*w7eg:4 y (: nqldero.
(a) What is the angle when he releases the rope?    $^{\circ} $
(b) What is the tension in the rope just before he releases it?    N
(c) What is the maximum tension in the rope?    N

  In the rope climb, a 72-kg athlete climbs a vertical distance )n3 n,i cwo9slof 5.0 m in 9.0 s. What minimum power output was used to accomplish this fea 3ninws)9 ocl,t?    W

  Some electric-power companies use water z+j 2uf(qq vdog+yu)(to store energy. Water is pumped by reversible turbine pumps from a low to a high reservoir. To store u )2zyd(ovuj (+q f+qgthe energy produced in 1.0 hour by a 120-MW ($120\times10^{6}$W) electric-power plant, how many cubic meters of water will have to be pumped from the lower to the upper reservoir? Assume the upper reservoir is 520 m above the lower and we can neglect the small change in depths within each. Water has a mass of 1000 kg for every 1$m^3$.    $m^3$

  A spring with spring stiffness constant k is cutudig/mi 7 dqb2l 6y4gl/hw-*m in half. What is the spring stiffness constant/q6wmu2 / dlb7*dmighgyl- 4 i for each of the two resulting springs?   k

  A 6.0-kg block is pushed 8.0 m up a rough hmyng8e2bp *feq.1 n 6)o.l uj +sv4ih37 $^{\circ} $ inclined plane by a horizontal force of 75 N. If the initial speed of the block is 2.2m/s up the plane and a constant kinetic friction force of 25 N opposes the motion, calculate
(a) the initial kinetic energy of the block; $\approx$    J
(b) the work done by the 75-N force; $\approx$    J
(c) the work done by the friction force;    J
(d) the work done by gravity;$\approx$    J
(e) the work done by the normal force;    J
(f) the final kinetic energy of the block.$\approx$    J

  If a 1500-kg car can accelerate 95 if/vm1u uzrfrom 35km/h to 55km/h in 3.2 s, how long will it take to accelerate from 55km/h to 75km/h Assume the p 51uu/9fmizr vower stays the same, and neglect frictional losses.    s

  In a common test for cardiac funczomy;. l ksx5.r4b m6ction (the “stress test”), the patient walks on an inc. sbkx 4 omzl6.c;y5mrlined treadmill (Fig. 6–46). Estimate the power required from a 75-kg patient when the treadmill is sloping at an angle of 15 $^{\circ} $ and the velocity is 3.3km/h (How does this power compare to the power rating of a light bulb?)$\approx$    W

  (a) If a volcano spews a 500-kg rock ve7 9hvuc r (pw+a;rq8sortically upward a distance of 500 m, what was its velocity when it left thhq+(sw97u croa v; 8rpe volcano? $\approx$    m/s
(b) If the volcano spews the equivalent of 1000 rocks of this size every minute, what is its power output? $\approx$ $a\times10^b$ W a =    b =   

  Water falls onto a water wheel from a. mxs sm;k cve;o+wx2ire9j4. height of 2.0 m at a rate of 95kg/s (a) If this water wheel is set up to provide electricity output, what iso.xcs2ik .j wme e+mx9r4 ;s;v its maximum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s