In what ways is the word “work” as used in eve;)sl6aocn+..y bn+esa/ set rryday language the same as that defined +.sb ls o .;e+ct/)6neyra sanin physics? In what ways is it different? Give examples of both.

Can a centripetal force ever do work on an object? Explainskc59 jp5kjt q(.l6)lc 4ujlsid6yr*.

Can the normal force on an object eyckpn19br8 5 3knwu7ur g z70ever do work? Explain.

A woman swimming upstream is not moving with respect to the shore. Is she n mn1.w ;t*1y+tsb fwedoing any work? If she stops s 1tyn+ *wstmfnw e;b1.wimming and merely floats, is work done on her?

Is the work done by kinetic friction forces always n0t h o2,ek3t4nmi,ce f8jq:rgu s* 2j5kzo vn6egative? [Hint: Consider what happens to the dishe fn6khjru 5*c23oeokg2 tvi0z,e4njqt8ms ,: s when you pull a tablecloth out from under them.]

Why is it tiring to push hard against a solid wall evenyu;94 cxx p.ne0hcy 5b though you are doing no woc. h5 e9x4 bynp0cu;xyrk?

You have two springs that are identical except that spring l is stiffer than r6*7 sn ef 6rxg. sp(9fbobd,r-utup;springtr;ernpp-xs 6b9f *uo(f7d,6.bgsur 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 horijw uye6 h1y(8xzontal force on a block 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 traveled a w8yy jeh6u( 1xdistance $d$ 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 graviu6o idc 9m;3der s4)xttational potential energy change when you x64;u3 o9tdrm s) edcijump as high as you can?

In Fig. 6–31, water balloons are tossed froetahv0k+y:+*j o tg;q m the roof of a building, all with the same speed but with different launch angles. Which one has the highest speed on impa +yto+* jthek v;qg0:act? Ignore air resistance.

A pendulum is launched from a point that is a height h above its lowny a;p o51wc5ia11vokest point in twoyn5k1a1v p1ow5c a;io 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 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 h6i +u5 lvt8 n+crei:/-bmbga compress the spring by pressing down with your hand a l8n/um6i-ebhvcg rbi :a5++ tnd then release it, can the spring leave the table? Explain, using the law of conservation of energy.

A bowling ball is hung from the ceili)9)+8hdzhnsk mu3b efx z ;be;ng by a steel wire (Fig. 6–33). The instructor pulls the ball back and stands against the wall with the ball agais)k9b ;z;fm)b83d e +nhuxhzenst his nose. To avoid injury the instructor is supposed to release the ball without pushing it. Why?

What happens to the gravitational potential s1sxp, mah;i16 umu3zenergy when water at the top of a watepmmisx 1 ,au1uz3h s;6rfall falls to the pool below?

Describe the energy transformations when a child hops around onnx- s)t p7qx rlixd-4/ a pogo stick.

Describe the energy transformations that take place when a skier starts ski2rx97i-dd nwf6xu6vying down a hill, but after a time is brought to rest by snx 7drwdxvf2669-y u itriking a snowdrift.

A child on a sled (total mass m) starts from rest at the top of a kz4b,z jp pdbi;.qgd 8g5/3dghill of height h and slides down. Does the velocity at the bottom depend on tzgpq 5 j3di,;d4gb8g.kpz/d bhe 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 u ofs:t9v:l. igzt -/wover a fallen log in their path rather than stepping on tz u- 9/g:.wovst:tlfiop and jumping down on the other side. Explain.

Two identical arrows, one with twice the speed of the other, are fir9fb)h0q q; xzt7x4w4r 4 d)qag.poovr ed into a bale of hay. Assuming the hay exerts a constant frictional force on the arrows, the faster arrow will penetrate how much farther than the slower49 4)wa pgoo7q4b0qz.)rdxrvq hf;t x arrow? Explain.

Analyze the motion of a simple swinging pendulum in terms of ener gaih)evjr *;66h *zxwgy, (a) ignoring friction, and (b) taking friction into account. Explain why a grandfather clock has to ze *;)hvriwx a*hgj66be wound up.

When a “superball” is drop h7b8:nbcd jhb,r ;x)xped, can it rebound to a height greater than its original hebbd; xx )hj rcnb,:8h7ight? Explain.

Suppose you lift a suitcase from the floor to a table. The work you do on xcscf3ji.e9;the suitcase depends on which of the following: (a) whether you lift i.3isce; 9xcfj t straight up or along a more complicated path, (b) the time it takes, (c) the height of the table, and (d) the weight of the suitcase?

Repeat Question 22 for t66; wf lbr5vd n5rzr(tw2y2u ahe power needed rather than the work.

Why is it easier to climb a mountain virt -ym h-lm -cz6 rm0jhhmp6/8a a zigzag trail than to climb straight u- 8zm mr 606l y-mth-r/hcmhjpp?

Recall from Chapter 4, Example 4–14, that you qp)gc1my0d9 rcan use a pulley and ropes to decrease the force needed to raise a heavy load (see Fig. 6–34). But for dm1pq c9ygr 0)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 gravio qegf20y4g) jtational force when a 265-kg pile driver falls 2.80 m?oq gg24 0ye)fj    J

  A 65.0-kg firefighter climb os6*i.1 *okyrog; t*5uuqohp7,mfphs a flight of stairs 20.0 m high. How much work is requhfyo.; t6oo*mu k g o5us*r*pi1,7phqired?    J

  A 1300-N crate rests on the floor. How much r,h( rlq2ctb7x/n /s uwork is required to move it at constant speed (a) 4.0 m along the floor against a friction foslh2c,b7 /tq/ (rrux nrce of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (horizontally) pushing a 160-kg cri6kkc8a wh+ 1hate 10.3 m across a rough floor without acceleration, if the effective coefficient 6h cka +wkih81of friction was 0.50?    J

  A box of mass 5.0 kg is accele2g y 2.k3rn j,7ydalzp5nmi5 jrated by a force across a floor at a rate of for 7.0 s. Fin.ym5 2n g3pk7zj aly,25rnjdid the net work done on the box.   J

  Eight books, each 4.3 cm thick with mass 1.7 kg, lie flat on a tabl:xeu( jf)x-ib+n wqi*e. How much work is required to stack themqju*+bx)xi-en fw i:( one on top of another?    J

A lever such as that shown i *z ryol//qg. z;vzu(un Fig. 6-35 can be used to liff objects we might not o vz r;u*/ly(u ogqz.z/therwise 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 3.6ar.mw - mw-ih07mp+b6a;m u qz m down a 28° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline (Fig. 6-36).umia-a 07r6 m.;b +z-wqmhwmp 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 ofzv2e+ mqt t6 z sq,bh,;*lqxsrt6i)3c mass M an acceleration of 0.10 g e6s3)rx+b6 sh tcvlq ;,iqt,qzzt * 2mupward.    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 disy ccxs2zmy(wa0wp/*vc :2xb,tance 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, varies as shownx69x oxk-d2xxpdn p0 - in Fig. 6–37. Determin-n 06d-xppx92 xx odxke the work done by 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 exerted on a partics:s )vr(gr,ojn 8xtk2al: 1yole 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 mol 9cfy. rxu 08x+kvx+kuecule, with 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 doubled, by what factor has its ;nsa 1x5 p 78:qv*ryd myyhl6qspeed 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 electrotb h; 6gg-sww00ztpa . -o3sjhn $\left(m=9.11\times10^{-31}\mathrm{~kg}\right)$ 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 travv1u44ckbweoo .4sx s*eling at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whose string exerts an afv/v mauby99e;ei :n yb+()ti6l pv:e verage force of 110 N on the arrow over a dista9:e; f6iylv )et9iuva(:+vbey p/mbnnce of 78 cm. What is the speed of the arrow as it leaves the bow?    m/s

  A baseball (m=140kg) traveling 32m/s moves a w ). k8owaqxno/ 4i-5-bvdwy bx0z8 dxfielder’s glove backward 25 cm when the ball is caught. What was the average force exerted by the ball on the glox oikx05wn- ydv-bq) bwo d/48zx8a.wve?    N

If the speed of a car is increased by 50%;hyl*0rkrx0 v , by what factor will its minimum braking distance be increased, assuming all else is the vkl r0;yr*x0h same? Ignore the driver’s reaction time.

  At an accident scene on a level roadfri,h 02eebp/, 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 ca/f0,p2eeir h br 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 reak ;kts +vl5.ffches the plate, it may have slo. fv 5slft;kk+wed by 10%. Neglecting 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 someone wh2u iqpr(xy25ho does 80.0 J of work on it? Neglect air resistapryui(h 5 qx22nce.    m

  A 285-kg load is lifted 22.0 m vertopqmx0,++s+le yw -v pically with an acceleration by a single cab+ppws e+ +-lxv yo0,mqle. Determine
(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 stiff it1vy xq, d5e0ml v0(jxvpgy+ru7o7;; i vz*aness constant, k, of 440N/m How much must this spring be stretchv07+vx,tqxrdg75p;a u l0yjv 1 imeiovy (z;*ed to store 25 J of potential energy?    m

  A 7.0-kg monkey swings from one branch to another 1.2 m highv c ju,8e+o-nver. What is the change in potentia-euvn j,c+8vo l energy?    J

  By how much does the lhg.uat+2 p(rqc (v2j6c1vb zgravitational potential energy of a 64-kg pole vaulter change if his center of6v cjtc +qz1 a2v(2prhu(l.g b mass rises about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizontal surface has speed v = 65 kmbds29 ,e0vu)lor a7kx /h when it strikes a horizontal coiled spring and is brought to rest in a distance of 2.2 m. What is the spring stiffness constant of207ka ,sxedvluob r9) the spring?    N/m

  A 1.60-m tall person lifts a 2.10-kg book from the grp0h 5bmr7u0q v:yx 9mhound so it is 2.20 m above the groh:m9bv u 70y05mr xpqhund. 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 and climbs to the top ofzua4k eo/yfmh: (e5x;/si1 fn a 3300-m /(fhsmzu 1 ;: 4neya/5if xokepeak.
(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 oflzk:vn.g4 sg ok7ta ,/p8ybgg1g 6 ql+ the spring is next to the 15-cm gnoa.8lbg6: ,g7gqkl /+szv1kygtp4 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 Tarzan, is running at top speed (5.3m/s) and grabs a/bc6f 17jjokm-.z lfi vine hanging vertically from a tall tree in the jungle. How high can she l -o6.m jjz7f/fb kc1iswing upward?    m
Does the length of the vine affect your answer? ----待选择----yesno 

  A novice skier, starting from rest, slides down a fricv9v gm ,v7b6viuef +6etionless 35.0$^{\circ}$ incline whose vertical height is 185 m. How fast is she going when she reaches the bottom?    m/s

  A sled is initially given a shove up a frictioyxl qn3m/m 9i1*/z0w ;j ofvzjnless 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 kine .r1k,tb1q e99yuhg/x x6nx iitic energy is transformed into gravitational potential energy without the aid of a pole. With what minimum speed must Fran leave the ground tkg ubqyirx ,19xx/nhe9.61iin 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 platfodogw4t 80v ,g ngi0g3frm with a speed ofdv,noi0wtg f03g 4g8 g 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/3gpqh:o k/c z is 950N/m is attached to a table and is compressed down 0.150 m. (a) What upward spq3 czk/po/h:g eed 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 friku- j a 6ya;cr*1cg-ebction 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 radiuc 1ea;ak-rj*gy-6ub cs 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 (spring stiffe o iv iu*d5xofy54)l0 ujqg:/ness constant k), Fig. 6–4i*55o xoil gjeu )f/duq4v:0y0. 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 jumper jumps from a bridge. She iszs, iu 2f8y3mk tied to a bungee cord whose unstretched length is 12f mzi3sk8 ,yu2 m, and falls a 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 ub ;ls p8-k2 to)y;bdnip to point 1 where it is released from rest. Assuming no friction, calcuk;l 8 yp2stid-b) bn;olate 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 at an angle of 33 5tf1 164. x2yotoggo 4avbopp $^{\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 elevaxs7rj re8. i8qtor 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 shoul r8q7e8x. rsjid have so that passengers undergo an acceleration of no more than 5.0 g when brought to rest. Let M be the total mass of the elevator and passengers.

  A cyclist intends to cycle f0d nb-q 95:g,wewdez 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, eac qeiv/4rshnme:j./v* h of mass 7650 kg and traveling 95km/h in opposite directions, collide head-on and come to rest. How much thermal enere: vv4/sehiq/*rn. mjgy is produced in this collision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slp c*2dvw0lgt xa3j w;via.:+wide 3.5 m high and reaches the bottom with a speed of 2.2m/s How much thermal +*2d.vwx wav i3waj :gltp0c;energy due to friction was generated in this process?    J

  A ski starts from rest and suyvc rb/ * h*4*tm*izvlides 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 13.0 m above the ground.9,wk )7m o ajrkb 11fdl8hi9se
(a) With what speed would it hit the ground if air resistance could be ignored?    m/s
(b) If it actually hits the ground with a speed of 8m/s what is the average force of air resistance exerted on it?    N

  You drop a ball from a height of 2.0 m, and it bounces back to a height of 1.5xtkl kl+-4 gh: m.k:h lt gk+-4lx
(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 withwdrd.vi;* x: g a constant horizontal force of 350 N. For the first 15 m the floor is frictionless, and for the next 15 m ; *i. xd:wrdgvthe coefficient of friction is 0.30. What is the final speed of the crate?    m/s

  Suppose the roller coaster in Fig. 6–41 pasdce hfy5+t.e:unf4 -qses point 1 with a speed of If the average force of friction is equal to oneny:h5ftu.df- qc +4 ee-fifth 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 *f5i gee otve em*:m1lcf+t;nr p98 0pupward 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 2g+- tl fk/5lnxg*l2amw,d zrspring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compressed 5.0 cm and released, stretches out 2.3 cm beyond the equilibrium position before stopping and turning back. What iwllda* m5 x, z2gr2f-nt lk+/gs the coefficient of kinetic friction between the block and the table?   

  A 280-g wood block is firmly attached to a ver(m uc6,e +hs r+91x*jmbxme cry light 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 released from this position, hom9r hcs ,urm6eec+* bx m(1jx+w far beyond its equilibrium position will it stretch on its first swing?    m

  Early test flights for the spac1mr7e;4 g62b+h bm( emp yqueie shuttle used a “glider” (mass of 980 kg including pilot) that was launched horizontally at 500km/h from a heigh4im qbgu+1er b 2peme y7(h;6mt of 3500 m. The glider eventually landed at a speed of 200km/h (a) What would its landing speed have been in the absence of air resistance?$\approx$    km/h
(b) What was the average force of air resistance exerted on it if it came in at a constant glide of 10 $^{\circ} $ to the Earth?$\approx$    N

  How long will it take a 1750-W motor to lift a 315-kg piano tzks (lp )8ya6co a sixth-story window 16.0 m above? 86 kl)zaps yc(   s

  If a car generates 18 hp when traveling a)l mgz65r v59 ck,tabzbaffr8k3oi1 )t a steady 88km/h what must be the average force exerted on the car due to friction and air resistar6k8kgi9 ))frf1octa5vlb,z5azm 3b nce?    N

  A 1400-kg sports car accelerates from rest to 95km/h in 7.4 s. What is the v*lkwu63 qm l:average power deli6 3kwl lm:*quvvered by the engine?$\approx$    hp

  (a) Show that one Brislmhh 9m+ yt2f)a-i+t tish 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 often expressed in the for374 dfd8owv lied5.q)bnpu8 em 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 p1kyqw 650bvze k2a5 x+pvc d (fa3a2u1150-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 h5p(5kcf ad2p 60q 2aa1wezkv3vxbu+yp) is needed to keep the car traveling at a constant 75km/h.    hp

  How much work can a 3.0-hp motor do i3 fi7 nm*m6pwcn 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates a 7.3-kg shotj2ravmfxe86417x l m-r xty1m from rest to 14m/s If this motion takes 1.5 s, what average power was devrvfj1mme -4a1x6l72xyr t8mx eloped?$\approx$    W

  A pump is to lift 18.0 kg of watec/uouqae d/ (aiiy*h+,f 2:fmr per minute through a height of 3.60 m. What output rating (w/oi q,*/ ha(:2mu+u f dacieyfatts) should the pump motor have?    W

  During a workout, the footba8dq .nk.3e h k8ubrn 5w.14b v*qrq smyq3nb6all players at State U. ran up the stadium stairs in 66 s. The stairs ar3ybqs. 65*.qqk.r8ad w e3nrkbuh m q8 bv14nne 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 climbt808./k+h1d9 4 bt yyh krmyldqsbul8 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 can it qv ): ldl:xbk z2g/mp/climb at g plzb/vk )l m:x/qd:2a constant 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 box alongo zr yyc/ bg/ux)r/g1* a level floor at a speed of 1.2m/s iur yzg/gbx/ry)o/ 1 *cf the coefficient of friction is 0.45?    hp

  A bicyclist coasts down lj,b6t 6d -g 2jqah-5kfuu,ai a 7.0 $^{\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” that are desxd j7+lf( ras2igned to compress and rebound elastically without any physical damage at speeds below 8km/h If the material of the bumpers permanently deforms after a cox7 2srlfa+d(jmpression 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 jsl*vhyo )w b9js5 /3vfirst shelf is 10.0 cm off the ground, and the remaining four shelves are each spaced 30.0 cm above the previous one. If the average book has a mass of 1.5 kg with a height of 21 cm, and an average shelf holds 25 books, how much work is required to fill all the shelves, assuming t 3 slojs)j5v9*h vywb/he books are all laying flat on the floor to start? $\approx$    J

  A film of Jesse Owens’s fam t05:k-eit ra8 b:zfgvodp)q7ous long jump (Fig. 6–42) in the 1936 Olympics shows that his0agov8kf :)id:t -bzq5 7etrp 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 without frict(gikycwthvbg t5e51y:8 u929w;kfv kion along the looped track shown in Fig. 6–39 is to remain on the track at a1fggyk8hk2(t cwb59 iy5vewu9v: kt; ll 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 fro.owxo; oji3 6xm an aircraft without his parachute opening. He landed in a snowbank, creating a crater 1.1 m deepoox .oxj3;w i6, but survived with only minor injuries. 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 length L whose other endo9n0 svk*rhl6 is fixed (Fig. 6 *kv9 0nlsro6h–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 a 3700-m-highm6j y2a2( cvw0fqxf;fn m gok2 w-n0d+ mountain. The climb is made in 5.0 h starting at an elevation of 2300 m. Calculatem(00f q-yf+c;m kf nga6v2wxwd2noj2
(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 9vb en1 hkar 1pe/.n;nt :8g8zx20-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 Cabbqcu, xef ,gm0f7o46 lifornia claims that its lifts can move 47,000 people per hour. If the average bq46m uexg,f of07,cblift carries people about 200 m (vertically) higher, estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam at s-p ebab6 6h8bp9a5f zthe rate of 650kg/s and falls vertically 81 m before striking the turbine b 59 ahbsz-afp6e8p 6bblades. 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 coastw 5tecx x7adx w:)rk)0er with a circular vertical loop (Fig. 6–44), the difference in your ap: xxwaxwr 5t) e)dkc07parent 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 through it.    mg

  (a) If the human body could convert a cazt 5)g-g2hurl /a aso4ndy bar directly into work, how high could an 82-kg man climb a ladder if he were fueled by osg oz-h/l5)4 2 arguatne 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 an9)ziy4 k x3eer 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 bat vv3s9 l09r-;cahxzebhroom scale, the spring inside the scale compresses 0.60 mm, and it tells you your weight is 710 N. Now if you jump on z0vxahr-93vlc e;sb9 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, and swings out over a lake (o ap-tllo5+f+aiy3 5jFig. 6–45). He releases the rope whenp+y3tf5allij5-o + oa 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 of 5.0 m in .wak l.e qa.a8lq;hbyy5*v*i/yahj 0 9.0 s. What minimum power output was used to accomplish this*/5;. y.8lkq vhqaajlwyae*0hy aib. feat?    W

  Some electric-power companies uj5 *ez ep*oax6o.,t tpp5gq p t*c(.-kkszci /se water to store energy. Water is pumped by reversible turbine pumps from a low to a high reservoir. To store the energy produced in 1.0 hour by a .5kt tigpj**k - pxtszec/o56 ce(aqpp.z *,o120-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. What is the spring ho4s+ gt/b dx*stiffness constant for each of thes tb+d/4*ohgx two resulting springs?   k

  A 6.0-kg block is pushed 8e1a a c:v.gz3i.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 avky/tw ,u1 8etm;ls*tccelerate from 35km/h to 55km/h in 3.2 s, how long will it take to accelerate from s,l vut 8m/wtyt1e*;k 55km/h to 75km/h Assume the power stays the same, and neglect frictional losses.    s

  In a common test for cardiac function (the “stresd.97:rfv *uc2 n vy;k2vjkdsb qtae; 9s test”), the patient walks on an inclined treadmill (Fig. 6–46). Estimate the power requir972 tb:dr9ayj u v*vcq;.fvdk ;e sk2ned 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 d x ggb1;g i;78q1ui-4rdpq ctgistance of 500 m, what was its velocity whengi gu7q141g;ictq; brg8dpx - it left the 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 rate of 95kg/s (a)kb -.r0pn)( ,1yryjvbtn/52iw ,ioqvrfwpd2 If this water whe2qpywi,/)( n . dkb,vnb5rwoi0 y12-rfjvrp tel is set up 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