In what ways is the word “work” as used in everyday language the same as that mw0 bl1lw f/xom)rl 3(j;kxt9defined in physics? In what ways iofm (b /l 0t3wklx;xlwm1 rj9)s it different? Give examples of both.

Can a centripetal force ever do work o4 bwvgt+fr(w: n an object? Explain.

Can the normal force on an object ever do work? E r.v fa(k23kqz6 eiw-txplain.

A woman swimming upstream is not moving with respect to the cpx1 8wdnq:l3 shore. Is she doing any work? If she stops swimming and merely floats, is wor:3xnld w8p1c qk done on her?

Is the work done by kinetic friction aha : 1-:xxzypd9c-nh forces always negative? [Hint: Consider what happens to the dishes when you a9 dacxy 1:npx- hzh:-pull a tablecloth out from under them.]

Why is it tiring to p)l lvntk t;sq8bu:im rwh/u6b8-wx;6 ush hard against a solid wall even though you are doing no wixvqw86unbk mt/:-6) ; 8twb; ruhllsork?

You have two springs th8d ty yg5gu*: qd6. rarsl z8mus)d:0cat are identical except that spring l is stiffer than sprirq*r):0gs. mgatusyz8 : ddlucd5y 86ng 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 block that is frev/ i05q4h* rrift zipw39wo6ye to slide on a frictionless surface iq4 of p/i*5ri6v0t3 wzywrh9(Fig.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 your 0 4v-c5gjb8 b+mtkqf)prk 3kbgravitational potential energy change when you jump as high as kqb-b4 jkg 5+fr0cvt 8pm)kb3you can?

In Fig. 6–31, water balloons are tossed from the r1)z;if 9onkh2fgs qap..sfk7 oof of a building, all with ths;9 pifqkfa.g .)o 7 fnkz1h2se same speed but with different 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 above its lowest xl. zyjaw ,-fu 12ksh4point 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 pendul, 4-zf1kwaj2.y uhlsxum 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 mass m rests upright on a table. If you compres4 kjmfe0; h4its the spring by pressing down with your hand and then release it, can the spring leave the table? Explain, using the lkefi04mh 4;jtaw of conservation of energy.

A bowling ball is hung from the ceiling by a steel wire (Fig. 6–33). The ilp 7ybqy8i*i .nstructor pulls the ball back and stands against the wall with the ball against his nose. To a.yibq *y8lpi7void injury the instructor is supposed to release the ball without pushing it. Why?

What happens to the gravitational potential enerq5r0 chjkwp*g 8: e2;lo tezd+gy when water at the top of a waterfall falls 5roj *p e0lgt ;zd+2e 8cwqk:hto the pool below?

Describe the energy transformatioz .ah:s3 kj3q7mpia,lu yi1.vns when a child hops around on a pogo stick.

Describe the energy transformations that take place when a ski szsxa) :jz.iwpa0 )m:er starts skiing down a hill, but after a time is brought to rest by striking a s:pxzz. m)jsai0w ):asnowdrift.

A child on a sled (total mu g) ltc8r9yi35h3x bxass m) starts from rest at the 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 is icy and there is nlcg xrxu 5)i9y t3h38bo friction, and (b) there is friction (deep snow)?

Seasoned hikers prefer to step over a fallen log in their path rat;*s)pub+ jc92 8--5-bpfzku yl vmbo0m ifra oher than stepping on top and jumping down on the other side. Expm2osb9b+ f- mfu-z by0p )i5laru8o-jv ;c p*klain.

Two identical arrows, one with twice the speed of the other, are fired int6rba obhi, 7, *nyyz8ro a bale of hay. Asy7 h8zbobarry6 * n,,isuming 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 peja*ct;hg 9 yfonh5 6.mndulum in terms of energy, (a) ignoring friction, and (b) taking friction into account. Explain why a grandfather clock9oang. yh5fh6cj tm* ; has to be wound up.

When a “superball” is droppe 7oqzji5 4 36f;terywod, can it rebound to a height greater than its original height? Explainr z7t;eq4 oyojiw3 6f5.

Suppose you lift a suitcase from the floor to a table. The work yo pgd k+jfx;o2;u 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 height of the table, and gp fkj2 x+o;;d(d) the weight of the suitcase?

Repeat Question 22 for the poweclm2zh(cp 0 xx r,l))sr needed rather than the work.

Why is it easier to climb a mountain via a zigzag trail than to climb stra 4ydf;y- w5rr k5lirt3yz(lc2 ight up?ri-; rd2ftz cy l5k53wryly4 (

Recall from Chapter 4, Example 4–14, that you can use a pulle)*j z entzfz9/y and ropes to decrease the force needed to raise a heavy load (see Fig. 6–34). tzn9jz/ *fe z)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 34c frywe sqyl82j2j8 by the gravitational force when a 265-kg pile driver falls 2.80 cj wr8ly qf3s2yj248e m?    J

  A 65.0-kg firefighter climbs a flight of stairs 20.0 m highaiofq/+xzc x9 0.hbw /. How much work is requireh.+ wci /o9x0 /xqzbfad?    J

  A 1300-N crate rests on thi)enc0uw3j t. w:dt6h e floor. How much work is required to move it at constant speed (a) 4.0 m alonutdcw6e t j0n )iw.:h3g the floor against a friction force of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (ho4f00s yhkksv8 rizontally) pushing a 160-kg crate 10.3 m across a rough floor without acceleration, if the effective coefficient of friction fsh v00ysk k48was 0.50?    J

  A box of mass 5.0 kg is accelerated by a force acrwgold vi 27g:0+-zfuaoss a floor at a rate of for 7.0 s. Find the net work-i: 2favlg 0u+7zdwgo done on the box.   J

  Eight books, each 4.3 cm thick9+tjd+ h8z4 jet htr6s with mass 1.7 kg, lie flat on a table. How much work is required eh+4hdt9 8jttz+ 6jsrto stack them one on top of another?    J

A lever such as that shown in Fig. 6-35 ca6d+ v5 tq9gij(poum57x1o mds/rvkf1n be used to liff objects we might notpfo1rx1/( si mqk 6m7utvgv5+ 59jddo otherwise be able to liff. 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 kept from accepj3;2 0f aeovdlerating by a man who is pushing back on it parallel to thp2 fe a;jo3d0ve 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 0e w :p :gnz3nox9wgp2a helicopter of mass M an acceleration of 0.10 wzw2g :g0 :epnp n9o3xg 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 i)xc6 l9jl45m.mkzl d1um0cqpf ;md, g s 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 +(:(mbzrz gnr(qftg4 the x axis, varies as shown in Fig. 6–37. Determine the work done 4nrq(t:z(r(z b m+ggfby this force to 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 exerte63d, g 3xh9ohrkbnr0 bku(g ,nd 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, wz+pt9 :l alt3cith 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 doubledwfvj*qz n,w-n p:7;-7e)n /xp vf ovko, 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 electro zas:+fc40 nzen $\left(m=9.11\times10^{-31}\mathrm{~kg}\right)$ 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 travelibn0bigm*7(f qufoj tu(0.y/ vn jh+y .ng 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 of 110 5f9r m s0s 2enlhthh+m;4/t kmN on the arrow over a distance of 78 cm. What is the speed of the arrow as it le;f2mhshem9mtkh0+l /rts 54naves the bow?    m/s

  A baseball (m=140kg) traveling 32m/s moves a fielderx7knj t4-q*3ax.i+exk9 wgzc’s glove backward 25 cm when the ball is caught. What was thk n47egc93w.-kx+*q z a xxitje average force exerted by the ball on the glove?    N

If the speed of a car is i e.*p/jgwb24oux:d0t z v da-uncreased by 50%, by what factor will its minimum braking distance be increased, assuming all else eg:t 2audx-pjd w.zu/4 0b o*vis the same? Ignore the driver’s reaction time.

  At an accident scene on a level road, iaoz.(b,1ddex.v4imdxy6( lqm yn /9fnvestigators 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 driver slammed on (and locked) the brakes. (Why doesvzd dxmnl d yo46/ ab.9f( (ey,i.q1mx the car’s mass not matter?)    m/s

  A softball having a mass of 0.25 kg is pitched at By ths 7b8+3nikx)rhm o/l je time it reaches the plate, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resistance during a on+8)lbkm 7isx rh/3j 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 someone wbaeirj l(2ix)+ *rlf.ho does 80.0 J of work o)2 *af+ll r ejbx.iir(n it? Neglect air resistance.    m

  A 285-kg load is lifted 22.0 m vertically s 8kts )dg2jt *v 1w4hsj /y8apm-4w(rvzk6o cwith an acceleration by a single cable. D 4s(aspr)vczt2d 8/w o yt jmkkw v81g*-hs46jetermine
(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 con*.,bxjzcsyb6b le)* xstant, k, of 440N/m How much must this spring be stretched to store 25 J of potential energycb ly .**) bsejxbz6,x?    m

  A 7.0-kg monkey swings from o*c:t(zd mcsv/q9)cvj ne branch to another 1.2 m higher. What is the change q/ mc)(tv v 9c:s*cdzjin potential energy?    J

  By how much does the gravitational potential energy of a 64-kg pole vaultek pm/ww-psq 9 bm5wo(,r change if his center of mass rises about 4.0 m during the ju mb opk,w-5/9(w qwsmpmp?    J

  A 1200-kg car rolling on a horizontal surfswv6lu*ff+88 z:pic c ace has speed v = 65 km/h when it strikes a horizontal coiled spring and is brouglcc pw*8f s6 u8f+vzi:ht 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 frogw f. 9d*n5tbcm the ground so it is 2.20 m above the fdw c g*btn5.9ground. 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 amh2ki0/ qeg n0n elevation of 1600 m and climbs to the top of a 3300-m peak.0mnh2k 0/qgie
(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 sp9 b nc;s)/fprzring is next to the 9crfb)zn ;s/p15-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 the spring line up with the ruler marks?    cm

  Jane, looking for Tarzq lm ytjokn62: d19l i1tn.q+ian, is running at top speed (5.3m/s) and grabs a vine hanging vertically from a tall i mq . 16ytl91+q: jdtln2iokntree 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 ren ug y:w.kz0/)mx,injwr h6,lst, 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 nx7v5jh: nk u uys 2w6x h;**m.nq3hnp+y/hlna 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 erky0y z:nq71 1u6g vfwnergy is transformed into gravitational potential energy without the0y :wnz6 fq1yg17kr uv 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.    m/s

  A 65-kg trampoline artist jumps vertically upward from the top of a platform witp (4,wqzi/ wtmh azt(pmi,w4/qw 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 sti *oegdn06qyzoxoda *8x55 cqjt 9(xo0ffness constant is 950N/m is attached to a table and is compressed down **8(azd on yo te6jcxq0x g05o5odxq90.150 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 the looped track (j o2w; y-n5wi4o(jvpcwtw)vy ;ho. yshown in Fig. 6–39. If the block is to revy.ypj -;w5c hyo 4 ojtnv((2 ;wwowi)main on 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 attached to the end of a spring (sprdm0.+c491zhan c rcuuing stiffness constant k), Fig. 6–40. The block is given an init0c chnuur+a91mz.d4 c ial 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 ti 0udpi(. ozy, n++)piz i;whfued to a bungee cord whose unstretched length is 12 m, and falls ni+)f( zz;u0p ,p+y.d ihiowua total of 31 m. (a) 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 Fig. 6–41 is dragged u+thljvhgu:: xk(1f muc6+ c1n4: b arup to point 1 where it is released from rest. Assuming no friction, calculate the speed at:64+(jnxhugu f k: c1ar:1tc+bhumvl points
2    m/s
3    m/s
4    m/s

  A 0.40-kg ball is thrown with a speed of 12 hd2p(cl ;y9r9vt4k agm/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 lf /ct7d4hjv/ 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 mofdjclvt/7 /h4 re than 5.0 g when brought to rest. Let M be the total mass of the elevator and passengers.

  A cyclist intends to cyc +f+dzp,e7 qrple 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 kmm(cxud 6k 70ug and traveling 95km/h in opposite directions, collide head-on and come to rest. How much thermal energy is produced in this c(c0umxm7 d uk6ollision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slide 3.5 m high and reaches the bottom with a sp3 (auz)piud t(sx1od6eed of 2.2m/s How much thermal energy due to t(3xid)(uzuopsda61 friction was generated in this process?    J

  A ski starts from rest anxsz gy5duk xrptxo :*069r6bl:kk/ d p.-gc p.d slides 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 dropped from a tree 13.5nep* uzgrii ;(s:b( h0 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 bounce4 0b6zx gveyx2s back to a height of 1.5 m.x6 ge 0xvb24zy
(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 awv1s 4 gw/qc47gqgb5 ecross a floor with a constant horizontal force of v/gq5g w4w 7qecbsg14350 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 crate?    m/s

  Suppose the roller coaqfw w-q wdp1006rd(2fw bsj;gster in Fig. 6–41 passes point 1 with a speed of If the average force of friction is equal to one-fifthd;j( -fs2 6bww pdw010gwqqfr of its weight, with what speed will it reach point 2? The distance traveled is 45.0 m. $\approx$    m/s

  A skier traveling 12m/s reaches the foot of a steady upward 18.0 *lo3p1gnqvh p: s ,z3la(dt/m$^{\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 ligjtvp p*n-k6 w)ht horizontal spring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compressed 5.0 jvt)w-pp*6n kcm and released, stretches out 2.3 cm beyond the equilibrium 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 horizon*:eo0chh bof5 tal spring, Fig. 6–40. The block can slide along a table wc h0beh*of :o5here 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 beyond its equilibrium position will it stretch on its first swing?    m

  Early test flights for to/u43tbd,;c1 xfy+ 7cn a5vigs ,mbzmhe space shuttle 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 lan x,u b3c4 y7;macstn/ov, i5d1+gmzfbded 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 motor to lift a 315-kg piano 7rruby4h /(iqto a sixth-story window 16ib/h(4 rurq 7y.0 m above?    s

  If a car generates 18 hp when traveling at a steadf d s1w/fq;p9zy 88km/h what must be the average force exerted; pfd/qsz9 f1w on the car due to friction and air resistance?    N

  A 1400-kg sports car accelt1jsw* nh-p eb -(k,lzerates from rest to 95km/h in 7.4 s. What is the average power delivered by the* p b,kjnzl(-se-ht1 w engine?$\approx$    hp

  (a) Show that one British hort 29s xz.t.0vffqz**t24 uu zcn1pcedsepower$ \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 expresjhvm-i7+v ;d+/ gojm9 79f 9cxdeptwwsed 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 hev/0 aj67k uitsr 1150-kg 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 car tr uv/0jtik a67saveling at a constant 75km/h.    hp

  How much work can a 3.0-hp motor n/ w0lm jx;)0xss mse5do in 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates a 7.3-kg shot vb,5t:z ms, 7u6;rsp4tes yqqfrom rest to 14m/s If this motion takes 1.5 s, what average power was developed;tusqvp zsm:,qbe,6 54 7 ytrs?$\approx$    W

  A pump is to lift 18.0 kg of wawjt h3 vzj (;fmr28ju5ter per minute through a height of 3.60 m. What output rating t5whz(jv ;j3m rfu8j 2(watts) should the pump motor have?    W

  During a workout, the football players at Stat3 :s3apurx b vwh0nn8;e U. ran up the stadium stairs in 66 s. The stairs are 140 m long and inclined at an anwhn;un3 0pvar sb x83:gle 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 climb a 6.0 *z0xa.mop ys0$^{\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 oz;cdr8 dg)8u yf 120 hp. How steep a hill can it climb at a constant speed of 75km/h if the frictiona )cdug;8z8d ryl forces add up to 650 N?    $^{\circ} $

  What minimum horsepower(( /3cpzngvxa 7clgu1 must a motor have to be able to drag a 310-kg box along a level floor at a speed of 1.2m/s if the coefficient of friction is 0.45? g/acz g(lnupc17(3 xv    hp

  A bicyclist coasts down a 7.0ju*a*9uvh k wp24c 7dy+bwhb r5y9t* x $^{\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 bui:xutf+ d,fbm,y5 xt qrxi ,x(-lt “5mi/h(8km/h) bumpers” that 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 5 frq,b - f,xym ut+,:tdixxx(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,nr,t,o oop n:*z )ddq5 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 shel rz dntd:pn5 ,*oo)oq,f 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 lon+p6o0 k*tltfa6ukc.n 1 )mf0 kpn1wulg jump (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 spn)*k 10omallfu kp1.f+6 cwut6pnkt0eed 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 t+qwub 0u p2qu*rack shown in Fig. 6–39 is to remain on the track at all times, even at+bu q2upqw0u * 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 aircraf7m:g)sqg7o vst 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 35m/s esg s :77gv)qmostimate
(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 m56.v* bm)toqrdddc4 of length L whose other end is fixed (Fig. 6–d6 rmbd m)qoc dv4*5t.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 y , + ;c0bplcwfr1dxl+of a 3700-m-high mountain. The climb is made in 5.0 lcx 0;lf bw,y+ cp+rd1h starting at an elevation of 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 abo,0.l )ggvlcstsy7i 9mve 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 claims that its lifts can mzhb (vs 4cc:r:ove 47,000 people per hour. If vsc4( rbz::ch 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 at the rate of 650kg/s and 56 q z aoyvjaiyq(5.o4falls vertically 81 m before strik .o yzo(jyqaiav465q5ing 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 c4j m7s0mxsg 4 rtelarwr2-5/with a circular 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 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 thro2xs 4 m-w/0e rr5jcam4rs tlg7ugh it.    mg

  (a) If the human body could convert a candy bar directly into work, hhb y+4;b 4tslo0-;suwd1vgzwql; x: l ow high could an 82-kg man climb a ladder i;u zs o+w4lg;-vdx b1 h:qb;tllys4w0f 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 a 9ztwf*6vp5c ri8e2r yn 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, qr591c:c27ac+ nomgra,v vhsg ki:q7 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 hei9 +5oc: n21vm7 a r:7chqsvagkrgqic,ght of 1.0 m, what does the scale read at its peak?    N

  A 65-kg student runs at 5m/s grabs a rope, and sw,ljj:8k8kuu h; 1k ldtings out over a lake (Fig. 6–45). He relt8:jkk;ld uuh ,1jkl8 eases 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 atphv k)hr6jn0osg216wpb zo :6hlete climbs a vertical distance of 5.0 m in 9.0 s. What minimum power output was used to s2b6 h0vz1n jrp:oko)pw 6 hg6accomplish this feat?    W

  Some electric-power companies use water to store en4/8b*036lrqh- chdyl ou u qx)a+dgecergy. Water is pumped by reversible turbine pumps from a low to a high reservoir. Todogll- *3urd0+heuh8q 46bc c y/a xq) store 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 stiffness constant k is cut in half. e qu;ouh3 zrhu z:h5e5s36ga,What is the spring stiffness constant for each of thes zruh 3:u5; 3hqez6u he,5oga two resulting springs?   k

  A 6.0-kg block is pusheo4 dio vje219hxmk,4b d 8.0 m up a 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/o,)n(db.zsqn t q1 :beh in 3.2 s, how long will it take to accelerate from 55km/h to 75km/h Assume the power stays the same, and neglect frictiondn,qnqs .zot()b:1ebal losses.    s

  In a common test for cardiac zam)8xh/gra .function (the “stress test”), the patient walks on an inclmzr/a)xg a8 h.ined 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 vertical1y rielcblm0.ps8+ e3.rsjr1 ly upward a distance of 500 m, what was its velocity when it left the volcano? 8+rrbrpl1j 3.si1m0el. cs ye$\approx$    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 wj(c 6l 6ysoha/ater wheel from a height of 2.0 m at a rate of 95kg/s (a) If this water wheel is set upjys 6/ ocal6h( 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