In what ways is the wo8sjo.m0m0xf.ki1sc lrd “work” as used in everyday language the same as that defined in physics? In what ways is it different? Give exampl sick mo0lsjf.0x8.m1 es of both.

Can a centripetal forc zag1egk p08l1 4+hivee ever do work on an object? Explain.

Can the normal force on an o4nt9 clg.db. ibject ever do work? Explain.

A woman swimming upstream is not moving with reij;u8q 2l ;o8,b bpvchxd(i h6spect to the shore. Is she doing any work? If she sd h 8ob2cqb;,(v;jpxh6u lii8tops swimming and merely floats, is work done on her?

Is the work done by kinetic friction forces always negative? [Hi45dyt:g b+zjtg2+s xjnt: Consider what happens to the dishes when you pull a tablecloth out from under thed: tb45+ jsjxg+z2gy tm.]

Why is it tiring to push hard against a solid wall even though you are doing no;elv(w/1ov 1hgtun7l vnll;o/vht(7g1uw1 e work?

You have two springs that are identical except that spring l ishrv/ r8f l8j-v3j9n sr stiffer than spring 2 v8/93rr rljhf jsvn- 8$(k_1>k_2).$ 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 horizo pm jq0c0borcxrs)g .v8yb/69ntal force on a block that is free to slide on a frictionless surface (Fig.crb0x9r. qo8v/ yj )6ms 0cgpb6-30). 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 u s kpxzmw89u5me95f(your gravitational potential energy change when you jump as higku z5m9s(wu 5 mxf98peh as you can?

In Fig. 6–31, water balloons are tossed from the roof of a building, all/l8yzqh .pc( gosq l82 with the same speed but with different launchsqqp .zolc28 h(/y gl8 angles. Which one has the highest speed on impact? Ignore air resistance.

A pendulum is launched from a point that is y;o 25r8fm clca height h above 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 is directed upward along the trajectory, and on the second launch it is directed downward along the trajectory. Which lau5oc; 2c r8ylfmnch 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;(v 3rsx rmy)5/j(9lui5 8*dp j 4eyfgfjrmzy the spring by pressing down with your hand and then release it, can the spring leave the table? Expla(x zyy l3y9;8ijf4jr5/sgmfu5p* jvr)(dermin, using the law of conservation of energy.

A bowling ball is hung from the3gm 8ml*. czry ceiling by a steel wire (Fig. 6–33). The instruc3 m mr.*gzylc8tor pulls the ball back and stands against the wall with the ball against his nose. To avoid injury the instructor is supposed to release the ball without pushing it. Why?

What happens to the gravitational potential energy when water at the n-s d-r3iy(dktop of a waterfall dk(s-r 3yd-nifalls to the pool below?

Describe the energy transformatilpmajs)1 u,b +f. v3iomv8;s yons when a child hops around on a pogo stick.

Describe the energy tkgs)6 7fcns4bwb j4nc-1nrj (ransformations that take place when a skier starts skiing down a hill, but after a time is broughw)4s4g jrncj(n-nskf 7 bc1b6t to rest by striking a snowdrift.

A child on a sled (total mass m) starts from rest at the top of a hill og h+3 htm7sw6zf height h and slides dohs +zm3t6gh7wwn. Does the velocity at the bottom depend on the angle of the hill if (a) it is icy and there is no friction, and (b) there is friction (deep snow)?

Seasoned hikers prefer to step over a fallen log it;e -u2 vfop/tn their path rather than stepping on top and jumping down on the other side. Expla/; evfp-ttu 2oin.

Two identical arrows, one with twice/:qzm ,bx)nnn the speed of the other, are fired into a bale of hay. Assuming the hay exerts a constant frictional force on the arrnqnm/):nzb, x ows, the faster arrow will penetrate how much farther than the slower arrow? Explain.

Analyze the motion of a simple 7g yxs0 2cji1u6s6hqe swinging pendulum in terms of energy, (a) ignoring friction, and (b) taking friction into account. Explain why a grandfather clo7iceq s6s6hyj21gux 0 ck has to be wound up.

When a “superball” is dropped, can it rebound to a height greater thqf,2 -j(p,qh7npbw g s0xxhm6an its original heighth-p7mgxwjbnp f06 qsqh,2(, x ? Explain.

Suppose you lift a suitcas*ze)l vs5 yh-qdk9(z be from the floor to a table. The work you do on 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, (c) the hei k(zq lbh5-)v9*yedsz ght of the table, and (d) the weight of the suitcase?

Repeat Question 22 for the power needed rather3zul7b)jy2ek6,/fjqi1s b qj7uti a) than the work.

Why is it easier to climbzs2hq5 cxf ;(r a mountain via a zigzag trail than to climb straight u(5sh;2qfx z crp?

Recall from Chapter 4, Exampqkb9pn dk fcp *r w1xl8;9oc*/le 4–14, that you can use a pulley and ropes to decrease the force needed to raise a/qfdc8 lpbo1crx*n w; 99*kkp 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 by the gravitational force when a 265-kg pile dkii75jg l 2sr.w l3b7qriver falls 2.gq si27 bk5 wij3l.lr780 m?    J

  A 65.0-kg firefighter climbs a flight of stairs 20.0 m high. How much jv06 vo n3gg;ework is requi6veogj0vg ;3 nred?    J

  A 1300-N crate rests on the fpchk6 r7(zaq4ouufn/s/g59 8 n7g z dgloor. How much work is required to move it at constant speed (a) 4.0 m along the flof9 snzgapr6 d/q /u7z475chkgu(g o8nor against a friction force of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (horizontally) pus zosa+ k.(guo;hing a 160-kg crate 10.3 m across a rough floor without acceleration, if the effective coefficient of friction ok(. sgzo +au;was 0.50?    J

  A box of mass 5.0 kg is accelerated by a forceqaa*)rd /m6 me across a floor at a rate of for 7.0 s. Find the net work done on the ba/ 6dmqa *)ermox.   J

  Eight books, each 4.3 cm thick with mass 1.7 kg, lie flat on a tabon r pz.*oi(l 2vi1gp2le. How much work is required to stack them one on top p2 lv*o go (2rzniip1.of another?    J

A lever such as that shown in Fig. 6-35 can be uqc/m vknp/v 3t6cr/ tl6c)cr 8sed to liff objects we might not otherwise be able to liff.kn)ct 3rc qlv/cmt68c 6//r pv Show that the ratio of 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° incline and is 6or9v5ax f*un kept from accelerating by a man who is pushing back on it parallel to thxnr9 *fv56oua e 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 xygg bff34m/))ef+h nhelicopter of mass M an acceleration of 0.10nf)hg y/em) 4+xfgf3 b g upward.    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 the distance axis is l:r cgwmgzr 6-**zsz9 iinear 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, acting along the x axis, varies as shown0 u9yg59tftpb4c5mgs)aw y 1we ; ;afy in Fig. 6–37. Determine the work done by this force to move the objectg14m95spt)eygwf a b w c;;yut0y9f5a (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 f7tvvd e)5tegf7( q8p on 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 mass lekq4 ;sr8(if7jjzi :o+jbu- e3 zga2 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 speepfy5xp6n veu/ b;u9u )d increased? $ \sqrt{a}$ a =    (b) If its speed is doubled, by what factor does its KE increase?   

  How much work is required to stop an electron 4dkxkkq iz ns:vnd-t74 3tzvw5:r03k $\left(m=9.11\times10^{-31}\mathrm{~kg}\right)$ 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 av*vrv5xf-j -8 y m5hbpvr 4u:wz8nw 4x5v cy+at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whose s :cdn, g80pyoak ;0ommtring exerts an average force of 110 N on the arrow over a distance of 78 cm. What is the speed of the arrow asc 0,m:o;ka g0dpmno 8y it leaves the bow?    m/s

  A baseball (m=140kg) traveling 32m/s moves a fielder’s glove backwarqe-j7dq 1siz n2q 8i7ld 25 cm when d 1inzqq87i s-7j qel2the ball is caught. What was the average force exerted by the ball on the glove?    N

If the speed of a car is 6a4z7 lhu,ewkincreased by 50%, by what factor will its minimum braking distance be increased, assu6u4,lkza ewh7 ming all else is the same? Ignore the driver’s reaction time.

  At an accident scene on a level r+twr0mod39 quh xr/3t oad, investigators measure a car’s skid mark to be 88 m long. The accident occurred on a rainy day, and the coefficient of kinetic friction was estimated to/rr q93m+d w 3hutt0xo 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 the time it reachesl/4y ./e-,zax gds4ky: xe bke the plate, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resistance during a pitch, if the distance betw:4y bg. sxdl4k ee /aex,/yz-keen 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 80.0zh./ 8 mgq/dwo J of work on it.gqw dh/8 /omz? Neglect air resistance.    m

  A 285-kg load is lifted 22.0 m vertically with an acceleration bb*qthka(u)v93h c. pnbv,t 7 qy a single cable. Detc*hat.v b9 7b)ht k3,qn vqpu(ermine
(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 spring stiffness co*7+o4d c08 vigiwas y:i8o4ek3b yhqanstant, k, of 440N/m How much must this spring be stretched to stork*yaai b qig3ev 78di:o0s+oy4 84wche 25 J of potential energy?    m

  A 7.0-kg monkey swings from one branch to0,9;f w6 qz53fs fyedukcri:zz,0qp o another 1.2 m higher. What is the change in wc5f 63 0izu,sqe9o qf:ypz ;,dzfkr0potential energy?    J

  By how much does the gravitational potential energy of a 64-kg pole vaulter chan64pi 4rowys:o 6/egdmge iiey/ o6ps4:wmrdg 46of his center of mass rises about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizontal surface has speed v = 65 km/h when :zxvwmlt ,(7;mpb69 9nw nmdjit strikes a horizontal coiled spring and is brought to rest in a distance of 2.2 m. What is the sn( x7 d6,j n ptvm;9mwb:wlz9mpring stiffness constant of the spring?    N/m

  A 1.60-m tall person lifts a 2.10-kg book from the ground so icg9 7-ipsza41c w9kfv t is 2.20 m above tkc1ac p9 9sz4gfv7-w ihe ground. What is the potential energy 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 at an elevation of 1600 m iq qn j8dt /u+6k.hp,iand climbs to the top of a 3300-m peak. n/qp .+8u,6kjt qi idh
(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 r.:n 0(cojo(o iovb:yto a ruler. The end of the spring is next to the 15-cm mark on the ruler. If a 2.5-kg mass is now attached (oyi:.o0vnor ob:(c jto the end of the spring, where will the end of the spring line up with the ruler marks?    cm

  Jane, looking for Tarzan, is runningdk .e/ysmb5-d. c itkc*e5n3i)ngi f0 at top speed (5.3m/s) and grabs a vine hanging vertically from a talmci*k3/if5dk0..tgcn eeybni5d)- sl 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, starting from rest, slides down a fric/imux,oh ka5 /tionless 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 khvthqpty. 5w6 *5a-h a shove up a frictionless 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 transformedet6 qf-hg a2;x m,c1yx into gravitational 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 2.10 m and cross the bar with a speed of 0.7m/s. 6ma gfx;qhct1-2 , xey   m/s

  A 65-kg trampoline artist jumps vertically upward from g n:3.n 1r:3jhkvl neythe top of a platform with a speednyjlv1rkhe .ng3 3: n: of 5.0 m/s. ($\alpha)$ 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 is 95dj6 y)em m/1wbf u0889oflnog0N/m is attached to a table and is compressed down 0.150 m. (a) What upward speed can it give to a 0.30-kg ball when w 81d 9jelf o)8mmfgub y0/no6released?    m/s
(b) How high above its original position (spring compressed) will the ball fly?    m

  A block of mass m slides withoqi xe+tl,;b3y2y3fe eut friction along the looped track shown in Fig. 6–39. If the block is to remain on the track, even at the top of the circle (whose radius is r), from what minimum height h must+t;efyb3 q3,eli2ye x it be released?    r

A block of mass m is at .k atir/fnu)+tached to the end of a spring (spring stiffness constant k), Fig. 6–)+ruf /knt.i a40. The block is given an initial 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 jumpe d42y8x5pzo x0swpjy/1gr7n u r jumps from a bridge. She is tied to a bungee cord whose unstretched length is 12 m, and falls a total of 31 m. (a) Calculate the spring stiffness constant k of the bungee cord, assuming Hooke’s law rpozw/8 0xpg7 5yds4 n2yx1ju applies. $\approx$    N/m
(b) Calculate the maximum acceleration she experiences. $\approx$   m/$s^2$

  The roller-coaster car shown in 4nipe6vbp+,6hceei0 uqid2 ;Fig. 6–41 is dragged up to point 1 where it is released from rest. Assuming no friction, calculate the ,0c6uv pi2 ne+i heqepb46d;ispeed at points
2    m/s
3    m/s
4    m/s

  A 0.40-kg ball is thrp+gcnbk r-ewv0(lf )q85 z)re own 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 nb-oim:zc5gj ,g d9*d to be placed at the bottom of an elevator shaft. If the elevator cable should break when the elevator is at a height h above the top of the spring, calculate the value that the spring stiffness constant k should have so that passengers undergo an acceleration of no more than 5.0 g when brought to rest. Le dj-o*n:mbg ,5g c9dizt M be the total mass of the elevator and passengers.

  A cyclist intends to c t zl3jlv7 nlfo3 i07;/qr:ebrycle 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 trae(v3:efbpnc i)93j f bveling 95km/h in opposite directions, collide head-on and come to rest. How much thermal energy is produced ibbf3fjcn3 ep 9(e:)vin this collision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slide 3.5 m high and y)0g5 gzu*cmnb/k gv70u 1un zreaches the bottom with a speed of 2.m5uu)/vbg0 nnzg 0 z1ckg 7*uy2m/s How much thermal energy due to friction was generated in this process?    J

  A ski starts from rest and slides s()ckp+ kgb1v*sh v4i down a 22 $^{\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 drop/0mxgd /ox1*ld syc1e lw.eoz;o9ad/ ped 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 g*iavg:bw +tz/9 do . ;odt1wxit bounces back to a height of 1.5 m. . x1g+a9: vo/z;dobit*dtw wg
(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, startin*(jk, eaq.7m/ aoxn*+ypg coqg from rest, is pulled across a floor with a constant horizontal force of 350 N. For the first 15 m the floor is frictionless, and for the next 15 m the coefficient of friction is 0.30. What is the final speed of the crateyqo/xa(*gak cpm.q en,7o*+j?    m/s

  Suppose the roller coaster in Fig. 6–41 pas1z)mn w:aph f64 m6atcz4mf3 zqvp.7cses point 1 with a speed of If the average force of friction is equal to one-fifth of its weight, with what speed wi3) mp14m cq mczn:.w ah 6vz476aftfzpll it reach point 2? The distance traveled is 45.0 m. $\approx$    m/s

  A skier traveling 12m/s reaches the foot of a stead xm*d xp4c8q2by 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 firmly attached to a very light hori n+b4hj0;w, t5mtje fxzontal 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 equilibriufwj je;nm504h +b,txtm position before stopping and turning back. What is the coefficient of kinetic friction between the block and the table?   

  A 280-g wood block is firmly attached to a very light hori w7kb,*bdfj32i fsk5 tzontal spring, Fig. 6–40. The block can slide along a table where the coefficient of friction is 0.30. A force of 22 N compress ksfi3bdf,k wt75* 2jbes the spring 18 cm. If the spring is released from this position, how far beyond its equilibrium position will it stretch on its first swing?    m

  Early test flights for the space shuttle used a “glider” (mass of 980 kg iijxs./m0dd(n3 d l1ly ncluding pilot) that was launched horizontally at 500km/h from a height of 3500 m. The glider eventually landed at a speed odx (ylm did. js301ln/f 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 motor to lift a 315- re j98d7xz,0hp+d 6lm gitoc;s(c8xkkg piano to a sixth-story window ecihdxj;km(od7rx +tz 0,s8 8 9lcp6g16.0 m above?    s

  If a car generates 18 hti:..t or3b:ze rg)oa p when traveling at a steady 88km/h what must be the average force exerted on the car due to friction and air rea:gb riret3.o).tzo: sistance?    N

  A 1400-kg sports car acceleratei z;6:nkz 7t9(2dgvcwrp b.qls from rest to 95km/h in 7.4 s. What is the average power deliveg6;l:nv kqz.9 rwdc(7tbpi z 2red by the engine?$\approx$    hp

  (a) Show that one British horsekfemj2pk;tj 5 f6 ;ze)power$ \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) ;6cq xlcu kd2uvvo;+ expressed in the form of “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-kj35.m 2w0kbo egchj3(+o/rskgj+ sksg car slows down from to 65km/h in about 6.0 s on the level when it is in neutral. Approximately what power (watts and hp) is needed to keep the.kc (jjr j0g s5hbwk s32mkgoo+ +3/es car traveling at a constant 75km/h.    hp

  How much work can a 3.0-hp mon0m.7re,zaw dzv/f i 4 fl0s/btor do in 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates-u s89 wuok7bn a 7.3-kg shot from rest to 14m/s If this motion takes 1.5 s, what average power was d7 8k9o-unwbuseveloped?$\approx$    W

  A pump is to lift 18.0 kg of water per minute through a height of 3.60 m. Wha7vjlbx a5/ dc83rau0m t o0cr da8b /lvamu5jx3 7utput rating (watts) should the pump motor have?    W

  During a workout, the football players at State U. ran up th hhk/s;w p271q b /2eooep (m0dh8/bexsjew8ve stadium stairs in 66 s. The stairs are 140 m long and inclined at an angle o;0/ hbs/(b/ep dwsekho22eq 178ex vmpj w8hof 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 cyclist climb a 6.0bb,5hd(+aii/m7dv1o7x see wdt,0p c $^{\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 ma.c)mp,3mrj t1* ev9goif n0tfximum power output of 120 hp. How steep a hill can it climb at a cti.c9) r3g,tnmjo pff0ev*1monstant speed of 75km/h if the frictional forces add up to 650 N?    $^{\circ} $

  What minimum horsepower must a motor have to be able to drag a 310-kg bo+k fiiv qke+: ic:jaview/-26x along a level-/ acq i:ejvw62kki++fv: eii floor at a speed of 1.2m/s if the coefficient of friction is 0.45?    hp

  A bicyclist coasts down a 7.0gdy4/0ttj w 8tv6e cj6 $^{\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 built “5mi/h(8km/h) bumpers” thrv ujd8 s42j4qd(un/ qo *1mynat are designed to compress and rebound elastically without any physical damage at speeds below 8km/h If the 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 majyd/sm n nruju *o2q(vq 4d418ss of 1300 kg and is tested by ramming into a solid wall? $a\times10^b$ N/m a =    b =   

  In a certain library thi.x*y pnz0e6 c5 on3rgawom;) e first shelf is 10.0 cm off the ground, and the remaining four shelves y*n)ox e or0cz65ai.wgmnp3 ; 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 is 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 lonvym.: c)sd6 + j0 0qjxxcg+-bq.gwdiq g jump (Fig. 6–42) in the 1936 Olympics shows that + dxcwjx:j+q g0)gvqs0-6mdc. .q yi bhis center of mass rose 1.1 m from launch point to the top of the arc. What minimum speed 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 withoutsq ipal*2l6lm 23u9vj4x nh0j friction along the looped track shown in Fig. 6–39 is to remain on the track at all times, even at the very top of the loop of i*3qlsla6up2vh4xj0 n9m lj2radius 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 37enh9bpy+a -o8 0 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.n-+bhapy9 8eo Assuming the pilot’s mass was 78 kg and his terminal velocity was 35m/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 ej/ 6j4uf,8vyb(ssvulength L whose other end is fixed (Fig. 6–43j ,(su6ue bfys/v j8v4).
(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 ispya/0u5h 3s g,8a9 ,spd+:cclf cy xkd made in 5.0 h starting at an elevation of 2300 m. Cas 3a 8,fas9+ cpl:,dx dk0yu/pcgch5 ylculate
(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 l;d;by, cqf0 mwhen a 920-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 California clavc 1baqrw n7(2 1 zwado5b7c,qims that its lifts can move 47,000 people per ho7a 1ac5 wrvqb bnoq,d2w7( cz1ur. If the average lift carries people about 200 m (vertically) higher, estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam 4eyv59kswu+hlo cjs 1 e4b1(lat the rate of 650kg/s and falls vertically 81 m before striking the turbine blades. Calculcbv (5hu4e+e 1l94lyw j kss1oate
(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 circulaqyq77min / ve:st,+ad r vertical loop (Fig. 6–44), the difference in your apparent weight 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 frictioq:eqi/y+ svmd, 77tnan. 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 candy bar directkq9et:t(pux ofk /4 f+g6xr) oly into work, how high could ko )tu4fo+rgkpxxq:6 /(t9f ean 82-kg man climb a ladder if he were fueled 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 an upward.qa1f, bdt za( 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 bathroz8fi9n(r4h(nlmav d,- uc c2 qom scale, the spring inside the scale compresses 0.60 mm, and it tells you your weight is 710 N. Now if you jump on the scale from a height of 1.0 m, what does-vcd,9cufn zr a8min2l4 ((hq the scale read at its peak?    N

  A 65-kg student runs at 5m/s grabs a rope w(faj 5h06qdu, and swings out over a lake (Fig. 6–45). He q05d wahf (j6ureleases the rope when his velocity is zero.
(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 o5:tj ,d9pffiq f 5.0 m in 9.0 s. What minim,tpjd:f5 q f9ium power output was used to accomplish this feat?    W

  Some electric-power companies use water to store vyvpx225i4b e energy. Water is pumped by reversible turbine pumps from a low to a high reservoir. To sto i2xby54ve v2pre the 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 stiffnessl wxf5, u5vjyv(7 c6)dtvjb1k constant k is cut in half. What is the spring stiffness l5 j5) 76v,vfj vy 1b(txkuwcdconstant for each of the two resulting springs?   k

  A 6.0-kg block is pushed 8.0 m up a rough2n ggyd/1 ys+x 37 $^{\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 from 35s)i;d 7n5z* uvonpuc4km/h to 55km/h in 3.2 s, how long will it take to accelerate from 55km/h to 75km/h Assume the power stays the same, andvc7so)p*d uni54;n zu neglect frictional losses.    s

  In a common test for cardiac function (the “stress test”), the patient walwf4f/v, wr m-qks on an inclined treadmill (Fig. 6–46). Estimate the power required from a 75-kg patient when the treadmill is sloping at an angle of qv fm-,ww rf4/15 $^{\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 vertically upward a distanceb e98g23m*3yo e;gftk7mi 3jwp(vs7o.irbg g of 500 m, what was its velocity when it left .2b3ep7gfbmg(jy i oe;7kr gtm*gos8v3 3w9 ithe 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 height of 2.0 m at a ratewv*t v f afxsh.4q)r:* of 95kg/s (a) If this water wheel is set up to provide electricity output, what is its maximum power outp.hqf4staw *:v)r vf x*ut?    W
(b) What is the speed of the water as it hits the wheel?    m/s