In what ways is the word “work” as used in everyday language nyf;s7 qygo e7+r5 o2jthe same as that defined in physics? In what ways is it differen+gsoqy5 y 27 j7rfo;ent? Give examples of both.

Can a centripetal fol :zt(73+n *skmnn tolrce ever do work on an object? Explain.

Can the normal force on an object ever do work? Explaitf, utm nmyy9v*- :ye3n.

A woman swimming upstream is not moving wpd71z+y0yo85 eq ryek ith respect to the shore. Is she doing any work? If she yqp7ye y +8k5drz10eostops swimming and merely floats, is work done on her?

Is the work done by kinetic friction forces always negative? [H bjs+7uyy fbmy;:u c21int: Consider what happens to the dishes when you pull a tableclot 1cb2jf sb7uy:;muy +yh out from under them.]

Why is it tiring to push haom7hvsj 5u 6bi(hb.6;9 kmh dsrd against a solid wall even though you are doing no wou5kh79hb6vh6 sjdb. i( sm m;ork?

You have two springs that are identical except that spring l is stiffex roe3lgm: n50 a8q5dcr than sprin mq8g5no3e:5a 0xrc ldg 2 $(k_1>k_2).$ 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 horizontal force on a ( 4nygv*fdy+xblock that is free to slide on a frictionless surface (Fig.6-30). The block starts from rest at þoint A, and by the time it has tr4dg nfyv*(y+x aveled 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 your gravitational potential energy c3 our x,vv cp0ib/hf:9hange when you jumpv9f:,rh v/3 xoucb0pi as high as you can?

In Fig. 6–31, water balloons are tossed ha-oer d-btx jf7 do-v1c3-+s53lhcifrom the roof of a building, all with the same speed but with different launch anglesjoa+cx-t1c ds hd --7ih3b-r5v e3ofl . Which one has the highest speed on impact? Ignore air resistance.

A pendulum is launched from a point that is a height h above its 0z: fxaxadg.wsc5h(.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 initx a d.(5:zgas wh0f.xcial velocity of the pendulum is 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 massp37g0vjs*bnq s 7*wxrlo ew 65 m rests upright on a table. If you compress the spring by pressing down with your hand and thexo3s** pv0s l 76wn eqjrbg5w7n release it, can the spring leave the table? Explain, using the law of conservation of energy.

A bowling ball is hung from the ceiling by a steel wir 8 b8zl;id+ld qr8of/v4)q rzse (Fig. 6–33). The instructor 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 w8 l+4rs o zl qb8qzr)8d;/vifdithout pushing it. Why?

What happens to the gravitational potential energy when water at the top ndfo:n40o1+ 9 yytlupof a waterfall fallsy9 t+n4du ny o:f1l0op to the pool below?

Describe the energy transfor -gg5abtp-fz, 1phnr 5)arf, umations when a child hops around on a pogo stick.

Describe the energy transformations that takeemydye6 6 sn: o7jrf.5 place when a skier starts skiing down a hill, but after a time is brought to rest by striking a snowdrfem5 66:yd rneyoj.s7 ift.

A child on a sled (total mass m) starts from rest at the top of a hill of v 8(,eknfzhzt9i:tj to 8(w o.height h and slides down. Does the velocity at the bottom depend on the angle of the hill if (a) it is icytwzkiht,8.(:vjo8 ze (9n oft and there is no friction, and (b) there is friction (deep snow)?

Seasoned hikers prefer to step over a guj2 jfl+*tu3 w;s(k6j*.lt/n bvos gfallen log in their path rather than stepping j/b*2( jg6sltv+.*kl ; ugswnju of3ton top and jumping down on the other side. Explain.

Two identical arrows, one with twice the speed of thc1 p6 7h6p.nypxls 2s /3msctoe other, are fired into a bale of ha.on1 c 6/s 3py7mphtxpl62scsy. Assuming the hay exerts a constant frictional force on the arrows, the faster arrow will penetrate how much farther than the slower arrow? Explain.

Analyze the motion of a simple swinging pendulum in q)*zqiy5ujo(aq62 j rterms of energy, (a) ignoring friction, and (b) taking friction into account. Explain why a grandfather clock hq* 6 qj5)riq(ju2zayo as to be wound up.

When a “superball” is dropped, can it rebound to a height greater than its udl 7 v6f5hztkx6stu8w 3 z(+horigin8f57h uwzlt6zh k(vx3d+ t6usal height? Explain.

Suppose you lift a suitcase from the floor to a table. The work you d,qyyk3l brj+. o 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 height of the table, and (d) the w.q yj3yl+r ,bkeight of the suitcase?

Repeat Question 22 for the power needed rather than the 9mog f( iu(3riwork.

Why is it easier to ) tdek( e1n6yaclimb a mountain via a zigzag trail than to climb straight up?) d(n6yetkae 1

Recall from Chapter 4, Example 4–lz3w4 8xx sj:y14, that you can use a pulley and ropes to decrex4y8js 3 zlwx:ase the force needed 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 by the gravitational force when a 265-kg pile driver falls. a65v ulu8dvd uuv6. ld85dva 2.80 m?    J

  A 65.0-kg firefighter climbs a flight of stairs 20.0 m high8-waxnrd 6b m). How much work is required)8w6 badr mnx-?    J

  A 1300-N crate rests on the floor. How much work is require280q-xheftnj ek s81f1sk8x ld to move it at constant speed (a) 4.0 m along the floor ee1x tfln18x8 8hs sq-k 2f0jkagainst a friction force of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did thed4+ 4,e5hhcf)offaodrs 7o3f movers do (horizontally) pushing a 160-kg crate 10.3 m ac o)7ff a4de hrfo+,d4ofs3c5hross a rough floor without acceleration, if the effective coefficient of friction was 0.50?    J

  A box of mass 5.0 kg is acceleratk;3rrek2,t. tjw*w ati, *uated by a force across a floor at a rate of forij.,w*wt u rr t2ekatk*3;a ,t 7.0 s. Find the net work done on the box.   J

  Eight books, each 4.3 cm thick with mass 1.7 kg, l w4vih,opc2or 2c jn0.ie flat on a table. How much work is required to stack them one on top ojc .24pr0nhv i,ocw2of another?    J

A lever such as that shown 6hpuhx2w77yo in Fig. 6-35 can be used to liff objects we might not otherwise be able to liff. Show that the ratiw2ox76hhup y 7o 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 d9.ouum,ug.2 ah1zx bis kept from accelerating by a man who is pushing backx,oh.dug za9u21umb . 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 f1u06l+f rer imass M an acceleration of 0.10 g upwar+ilf61fr 0reud.    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 gv2xshge 70lc. 0f5:5yt +vtv hkd/iddistance 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, acting along the x axis, variesnm 3lx3hc03xnpw .eick;p1 0 m as shown in Fig. 6–37. Determine the work done by this force to move the object (a) from x=0 m to x = 1 031pk 33hic pncmxewx.n;0lm0 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 ond .hs /iy*k9fe 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, w1ytt.5g,; s- 6bde*tzu rif1yaeq+ spith mass 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 dotabt )z 6z4haam:od: 6ubled, by what factor has its speed 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 s t6fohe3 h8z,$\left(m=9.11\times10^{-31}\mathrm{~kg}\right)$ 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 e2r wve3ka :2seuik7 +3y ftn31250-kgcar traveling at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whose string exerts an average force l;a),dx (taxcjhlfj2 fc4ocjv+p7 :33j 8arcof 110 N on the arrow over a distance of 78 cm. What is the speed of the arrow as it leaves the bow?+aalf:342jtjocj c (,j8 plf)3 xa;v7hrxcc d    m/s

  A baseball (m=140kg) traveling 32m/s moves a fielder’s glove backward 25 cm wheniqx c0 g*k;ao*/+b r4 ntvcfr f,ac40k the b4;, o*gnr 4c0c* tc0rkqvfai/ baxkf+all is caught. What was the average force exerted by the ball on the glove?    N

If the speed of a car is increased by 50%, by what fa8 / us t9rmf3d8icz)v g)zfb7c y+8qfxctor will its minimum braking distance be increased, assuz s8z b) 8mxvfu7f9+/ cc qr38gftdyi)ming all else is the same? Ignore the driver’s reaction time.

  At an accident scene o6h 0*j*hhx,27e teqfapai+ wu1upc w 2n a level road, 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 be 0.42. Use these data to determine the speed of the car when the 6wxc2j7eh1+h *uepqtuf h* wp2,aa0 idriver 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 reaches tjrv(k;w6 +w w/lx54m cxyg 3umhe plate, it may have slowed by 10%. Ne(gvr6;wk4m35w xc j +mwxuyl/glecting gravity, estimate the average force of air resistance during a pitch, if the distance 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 some;k,a d0s/x 5ui.( cqefgdjc*o one who does 80.0 J of work on it? Neglect air resistance. .koqu0 *fa;ge(5 j /ccids ,xd   m

  A 285-kg load is lifted 22.0 m vertically wo5daj grc766lt f;aq48 tcch*ith an acceleration by a single cable. Determin 6d c5tcat*;r6j8 7cgfo4hal qe
(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 coytzpsyj ;g jm inb)+0)2r ok,0nstant, k, of 440N/m How much must this spring b gm;2ksobyr,pn0jz t) )yij+0 e stretched to store 25 J of potential energy?    m

  A 7.0-kg monkey swings from one.f zs) z330v rq trp(0in5jtcr branch to another 1.2 m higher. What is the change in potential ernt fqr 3.r ( pz503zv0ci)jstnergy?    J

  By how much does the gravitational potential energy of a 64-kg pole vaulter rx+1fp2/k .b3 hdmxlo change hp2.l+dbxxrk1of/ 3m if his center of mass rises about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizonta9f-c06dz/w7o8 sjat4j z ddtndc 9 m8ol surface has speed v = 65 km/h when it strikes a horizontal coiled spring and is brought to rest in a distance of 2.2 m. What is the spring sctco8fm 8d-j9st6zad0do/4 zdjwn7 9tiffness constant of the spring?    N/m

  A 1.60-m tall person lifts a 2.10-kg book from theyc vhn mjq-2n .if/g*- ground so it is 2.20 m above the ground. What is the potential energy of the book relative t*cg./hf-qn v-m 2injy o
(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 and climbs to p.zbwj7)tkl 1the top of a 3300-m peak. pwk b j)zl7t.1
(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 t: mzs/b qu*t-next to 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 to the end of the spring, where will the end of thb utzq:-sm*t /e spring line up with the ruler marks?    cm

  Jane, looking for Tarzan, is running at top speed (5.3m/s) and grabs a vi phats wi48f33wg-u)i ne hanging vertically from a tall tree in the jungle. How high si3fuw 4 )ha-8twg3i pcan 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 jqjku3b my .(5frictionless 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 shovek kohmh/*y 06o 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 transformed into gravitationalld, q-jm nbe*, potential energy without the aid of a pole. With what minimum speed m-*dql,,ebn j 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.    m/s

  A 65-kg trampoline artist j3:bryl x ribd65we3j/ umps vertically upward from the top of a platform with wed3j/l6x:b 5 yr3ibra speed 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 ck2uaz ttky fst(*o 20x2s)sv9onstant is 950N/m is attached to a table and v 9)y us022o tt2sa kszftk(x*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 withoeg ..e2 wz tszzf1n5w/ut 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 it fse/t ze1nwzz w2g. 5.be released?    r

A block of mass m is attached to the end of a spring (sprig.-jegd,8te j ng stiffness constant k), Fig. 6–40. 8.jte g, e-jdgThe 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 jumper jumps from a bridge. She is tied to a bungee cord whos 1a ;rwol-6q zo8dj/jbe unstretched length is 12 m, and falls a total of 31 m. (a) Calculate the spring stiffness constant k of the bungee l jqbj;o 8zd-/6o1wra 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 Fig. 6–41 is dragged up tv7)/ bclj 9 v1sf)uv/i)fbxwg/ep(*3fesucko point 1 where it is released from rest. Assuming no 3p)7*1s v(cwl)egiksuff9u vvb/ f bejcx)/ / friction, calculate the speed at points
2    m/s
3    m/s
4    m/s

  A 0.40-kg ball is thrown with a speed of 12 m/s atw lf ypspntay nw1t /69;qk,)) 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 elevvqsu31k 4r;rw0h a6e aator 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 whre1k04q vrw;a6 su a3hen brought to rest. Let M be the total mass of the elevator and passengers.

  A cyclist intends to cycle r9w88 +9kp3qj+l wg,vf t5rbe.aj;npsy bst /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 massintd3y :f w+qvz (9 swp35mo-m 7650 kg and traveling 95km/h in opposite directions, collide head-on and come to rest. How much thermal energ:pmm39dot+qsnzv3-5if (y w wy is produced in this collision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slide 3.9(b6 gfl-cuteid6mvm.xp 65w5 m high and reaches the bottom with a speed of 2.2m/s How much thermal 5 vmifxel-6 9m 6bpd( .gtc6wuenergy due to friction was generated in this process?    J

  A ski starts from rest and slides down a 225 (ddjps5d4 tbwzo*cj26w g:d $^{\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 dropped from a t7 wc6u4k)ixst7 hqb bbs38a b(ree 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 1q(fhc xg; abyex-4:igmb ((ebounces back to a height of 1.5 m.y41 x (e(axh- c(ibf;q:ggmeb
(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 wi:y88p inbuky+l)y wb1th a constant horizontal force of 350 N. For the first 15 m the floor is fry 1wyb:)kbl8u+y8pni ictionless, and for the next 15 m the coefficient of friction is 0.30. What is the final speed of the crate?    m/s

  Suppose the roller coaster in Fig. 6–41 passes point (;2nsmaq;:xgh6gj 9 jjpvro )1 with a speed of If the average force of friction is equal to one-fifth of its weight, with what speer xg6 ao s(9vqnj;gm;:2j j)hpd will it reach point 2? The distance traveled is 45.0 m. $\approx$    m/s

  A skier traveling 12m/s reaches tdv1 aj6 q yr,r;ihiq2l/.o *pbhe 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 firmly attached to a very light horizontal sprintolks19rn7* ,kkr8y+e fp.wng (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 stopp srkyk98open*+1,k f. rw7lt ning 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 ligh2voe ./hxyx (vt horizontal spring, 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 releaseoehy /.(v2xvxd from this position, how far beyond its equilibrium position will it stretch on its first swing?    m

  Early test flights for the space shutty3jrkf5 -c r*cle used a “glider” (mass of 980 kg including pilot) that was launched horizontally at 500km/h from a height of 3500 m. The glider eventually landed at a spee5 * yc-rfrckj3d 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 motor to lift a 315-kg piac6.)shwd y m*tno to a sixth-story window 16.0 m ad cy )w.stm*6hbove?    s

  If a car generates 18 hp when travec)v*0v gfthd5ling at a steady 88km/h what must be the average force exerted on the car due to friction and air resis0c*tdvhvg 5)f tance?    N

  A 1400-kg sports car accelerates from rest t y )i:oa5,daplo 95km/h in 7.4 s. What is the average power delivered by th5) pdal,:iay oe engine?$\approx$    hp

  (a) Show that one Britishh0*u4wbo/t9qc y zgi o:x6q3o horsepower$ \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 oftl*qx;m8 z );r: xuegw a4sjx;oen 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-kg car slows down from to 65km/h in about 6c obd-6ovc fzu 6d5*g0ac04uy.0 s on the level when it is in neutral. Approximately what power (watts and hp) is needed to ke04gf coc60*d yu c dob-zavu56ep the car traveling at a constant 75km/h.    hp

  How much work can a 3.0-hp motor do i4yd-r oi/pp i2h0gsx,lq9tw .n 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerat v5ebiooci01 y5 :2kbjes a 7.3-kg shot from rest to 14m/s If this motion takes 1.5 s, what average poweb5c50:1kjvo byi2o ie r was developed?$\approx$    W

  A pump is to lift 18.je5vjl8cdp e5qw)y- f.n/a. m0 kg of water per minute through a height of 3.60 m. What output rating (watts) should the pump motore8q-a5/j d.5 myncl) v .jfpwe have?    W

  During a workout, the football players at State U. ran up the stadium stairs k0 5c94k9aev( mf-h) nnmybqsin 66 s. The stairs a4 ke fmmb nn09) aqy5vsh9c-k(re 140 m long 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 cyclist cliz/+ ega6 vmec4 ;pkv f;09guwbmb 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 output of 120 hp. How steep a hill ca) w 9gkwdjcc 0*(3l0hmiaqv :gn it climb at a constant speed of 75km/h if the frictional forces add up to 650 Nvh mdc9*30l a:0ic (gk)jwgqw?    $^{\circ} $

  What minimum horsepower must a motor have to be able to drag a 310-kg box alo, z8o.+7 yb if usfzn cmci8a-gle6(-cng a level floor at a speed lbf 7 i. -,88cuz+ic-cma6syegzfn(o of 1.2m/s if the coefficient of friction is 0.45?    hp

  A bicyclist coasts down a 7.0 m-dn3n:v jfu:$^{\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(8kemba5b0l0 yi 4a;vm9kq -qre:8wzr c:m/h) bumpers” that are designed to compress and rebound elastically without any physical damage at speqzw rq-bvl5m;ea4eb yia k9:00m r c8:eds 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 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 ground, ankv61r:ivqt9 0du ru3 vd 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 is required to fill all the shr6t0qu:r9 uk31vivdv elves, assuming the books are all laying flat on the floor to start? $\approx$    J

  A film of Jesse Owens’s famous long jump (Fig. 6–42) in t9,hq1 qoxq3x34 cyna she 1936 Olympics shows that his center of mass rose 1.1 m from launch point to the top of the arc. What minimum speed did he q,y3q3o 1s9hnq acx4x 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 f,woyvr di9 ( hr0wru0qj4*bb+riction along the looped track shown in Fig. 6–39 is to remain on t +9 oy qhr0vwr*u40j rwdi(bb,he 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 m after jumping from an aircraft withou0 5w)y5)atgj s-tu8ut)vw3a-ezay wj t his parachute opening. He landed in a snowbank, creating a crater 1.1 m deep, but survived with only minor injuries. Ast)-jtzwvuyw-)3ya u wajg55et s8)0asuming 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 length L whose other end i4*wn. .z q.srisg8lze s fixed (Fig. 6– s*. lz8gwq.zrnsi4.e 43).
(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-i 7dt3u1m ,6vrq(.ugaswial n5vra3 w7 czn6 a 3700-m-high mountain. The climb is made in 5.0 h starting at an elevation d 6us.1 6aga v7( ivr tzaq3,irmwu5n 3l7n-wcof 2300 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 920-kg elevator is 28 m above a huge spbctyd*+ ( tp qsj130poring ($k=2.2\times10^{5} \mathrm{N/m}$) 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 claims that its lifts can moht kp;- ttme* wj40la;ve 47,000 people per hour. If the average lift carries people ab* h-mp;j4twtk0ea tl; out 200 m (vertically) higher, estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam at the rx:4/ 7z cx- yso*66divbsi wjxate of 650kg/s and falls vertically 81 m before striking the turbi6bxxxz-wy7c/si: 4v id6 so* jne 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 ver*kubo b-r/, cvtical loop (Fig. 6–44), the difference in your apparent weight at the top of the ci/ ,vkb-u rcb*orcular 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 candy bar directly into q8dk ma* tna4nw7vwja* :7x4s work, how high could an 82-kg majm: qd 4 8w7 naavwsk*x*tn74an 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 acwsjjq1 ee 1 d3d rnuwa2* 557q/vi*ncngle 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 comprbl,gu9,es w (q9c) xwyfa,) jresses 0.60 mm, and it tells you your weight is 710 N. Now if ,yxu9)9 ,(rawe l,jbwg)f cqsyou 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 at 5m/s grabs a rope, anbago24qb)wo kae d 7/*g d)h/1 ghunu7e:8kr td swings out over a lake (Fig. 6–45). He releases the rope when hise 7 d/otkuurg n baeg:w)h2*h8k1o7 b4)ga/dq 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 cli k.jr+fd;kqpz t34vk-mbs a vertical distance of 5.0 m in 9.0 s. What minimum power output wakp +.f-kqj3 z 4krt;dvs used to accomplish this feat?    W

  Some electric-power companies use water to store (cqfh)7wvqpt ;h1a c8energy. Water is pumped by reversible turbine pumps from a low to a high reservoir. To store the enerh7w;q)v ca(81ph f cqtgy 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 constld3c81jvtf5by x2d+tf rg3s8ant k is cut in half. What is the spring stiffness constant for each8v2tfr8 l dg3j+cf1dx35 syb t of the two resulting springs?   k

  A 6.0-kg block is pushed 8.0 m up a rr4rq.dtqf/qn c0-+k rough 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 35km/h to 55km/h in 3.2 s, ozrter)*c ljog 4z)( kqn8.pz7lt8,p how long will it take to accelerate from 55km/h to 75km/h Assume the power stays the same, and neglect frictional rl) (z847pcnrjlg,e8pto o.z )ztk *qlosses.    s

  In a common test for cardiac function (the “stress test”), t*sl ugn75pii t 0; qfca/ehf4.he patient walks on an inclined treadmill (Fig. 6q7 .4 5 fft0glen/u shipc*i;a–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 vertically upward a dil8 y,svs6 1liapq1 g+pstance of 500 m, what was its velocity when it left the volcano? g p+1i8,vlsa ql61 syp $\approx$    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 watendd8d7 dq66bor wheel from a height of 2.0 m at a rate of 95kg/s (a) If this water wheel is set ddb o8 66qn7ddup to provide electricity output, what is its maximum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s