In what ways is the word x6rt)q1r4 zvi“work” as used in everyday language the same as that defined in physics? In what ways is itzqr 1)6 vtxir4 different? Give examples of both.

Can a centripetal force ever do work on an objek ;c )j7oj+ .cu0vzgzrct? Explain.

Can the normal force on an object ever do wo4p26ru7to/i mbs) se x3fub p/rk? Explain.

A woman swimming upstream is not mo9gw ku;gwqn+7ving with respect to the shore. Is she doing aqg+g; nwuw 79kny work? If she stops swimming and merely floats, is work done on her?

Is the work done by kinetic friction forces always negative? [Hint: Considh; 86h o8-nqfn+gg2jp*jg+sbgss- n(rhqm .a er what happens to the dishes when you pull a tablecloth out from under tg -*q+- hnb hso8ggf6r(;8jg h.qsjamn +2spnhem.]

Why is it tiring to push h1di6sa heo uec)ap)( * 7eyo.xard against a solid wall even though you are doing no acye7 a oeieu*() s6d1.xohp )work?

You have two springs that are ide n pa gd2-4i1b3unh,jng)7kkt ntical except that spring l is stiffer than sprn u3 dnhtgkjk7n4 ag -p1),b2iing 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 frp :b7c7 ageaz/ee to slide on a fri /7paaec :7bgzctionless surface (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 gravitatdb3 gai*bp3, hxb(( iirsv t*)ional potential energy change when you jump ai ,((tib3ibsrp*3ahdx b* g)v s high as you can?

In Fig. 6–31, water balloons are tossed from the rt149i. 4lw wwypck7g qoof of a building, all with the same speed but with different launch angles. Which one has the highest speed ogt y94lkqpi. 1w7wcw4 n impact? Ignore air resistance.

A pendulum is launched from a posn jxjax+o*p:ho-9 0 rint that is a height h above its lowest point in two different ways (Fig. 6–32). During both launches, the pendulum is given an initial speedrj9o0 nxj+shx:oa -* p 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 compress )wwb (4 l2y m9maex.psthe spring by pressing down with your hand and then release it, can the spring leave the table? Explain, using the law of conservatibs9 lw epmw4x.ay)2m( on of energy.

A bowling ball is hung from the ceimbf) f m :4:v/ccp 8xyv.k alob*el;9pling by a steel wire (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 opcfa vc)/mel 8xbm 4by*f 9:.lp;k v:to release the ball without pushing it. Why?

What happens to the gravitatpoy-w5 ap2r ;rional potential energy when water at the top of a waterfall falls to the pool belowwrp5 r-po;a2y ?

Describe the energy transformations when a child hops around on a pogo st 3zqy r1oi j...9bbfrxrw*1sbick.

Describe the energy transformations that take place when a skier starts 9i0see(jdi 0lx g;l8kqe 7y )uskiing down a hill, but after a time is brought to rest by striking a snowdrift.el8d0e jukqiigy (;)s x90e7l

A child on a sled (total mass m) starts from r5(b6x - 0ebm izxgqw1cest 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 ifxe5g b(qz60 wm1b -cix (a) it is icy and there is no friction, and (b) there is friction (deep snow)?

Seasoned hikers prefer to step over azxeqk8;ms)s 2 fallen log in their path rather than stepping on top and jumping down on the other side. Expxs sz82e);kqmlain.

Two identical arrows, one with twice the speed of the other, are fire/js :wm(hxa :ed into a bale of hay. Assuming the hay exerts as mh:(ea/wjx : constant frictional force on the arrows, the faster arrow will penetrate how much farther than the slower arrow? Explain.

Analyze the motion ocd0*g nk )hmw0bsv94(t l9ctlf a simple swinging pendulum in terms of energy, (a) ignoring friction, and (b) taking friction into account. Explain why a grandfather 0w)gckbd m9n9tlh lvcs0*4 ( tclock has to be wound up.

When a “superball” iez7 ypgn5q 5vb( (igx.s dropped, can it rebound to a height greater than its original height? Explai g7n(ve.q(pyzg b5ix5n.

Suppose you lift a suit9wrpdvp7n4 u6 case from the floor to a table. The work you do on the suitcase depends on which of the following: (a) whether u479p6 wvprn dyou lift it 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 fo2hzd)0lq1g jc r the power needed rather than the work.

Why is it easier to climb a mountain via a zigzag trail than ty +nh6o(2hjpz o climb straight upjh(o+6 2yh pnz?

Recall from Chapter 4, Example 4–14, that you can use a pulley and mh+ p0*hzf7 i-he+imeug5q y.ropes to decrease the force needed to raise a heavy load+ -ufm q7* +gieh.ehizpym05 h (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 gravitaf -g(3lz sd+ vt8dyc8ptional force when a 265-kg pile driver falls 2.80 m? 8 t3yczs8v(dgp+ d-lf    J

  A 65.0-kg firefighter climbs a flight of stairs 20.0 m high. How much work is re 50z9enttla2uu0 tsq9quired?uaetn0lqsuz 9295t0t    J

  A 1300-N crate rests on the floor. How much woriw 6 jswsf.(l;aq-w( lp (vmm4k is required to move it at constantq4- wmvw6;lp wl(j ( .mfis(as speed (a) 4.0 m along the floor against a friction force of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (horizontally) pyv,2td(b4wt r6/ho cyushing a 160-kg crate 10.3 m across(c4 h6/vwty bdy 2o,rt a rough floor without acceleration, if the effective coefficient of friction was 0.50?    J

  A box of mass 5.0 kgt(55 s0lvctej2iw4p n is accelerated by a force across a floor at a rate of for 7.0 w( n2pc 54etlijtv0s5s. Find the net work done on the box.   J

  Eight books, each 4.3 cm thick with mass 1.7 kg, lie flat on a table. How -g+hg5)nsg9lek z3 yemuch work is required to stack th )-ze3egn9sh l+ k5gygem one on top of another?    J

A lever such as that shown in Fig. 6-35 can be used to liff objects we might no*4vqr e u4sep 0euc:rp-/tnx-t otherwise n-v* e0ucexpsrtr4u:4q - /pebe 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 usc4rq - 4(lj7xx4v mukept from accelerating by a man who is pushing back on it parallell-4 m4q rvuj x(su7xc4 to the incline (Fig. 6-36). The effective coefficient of kinetic friction is 0.40. Calculate:
(a) the force exerted by the man,    N
$(b)$ the work done by the man on the piano,    J
$(c)$ the work done by the friction force,   J
$(d)$ the work done by the force of gravity,   J
$(e)$ the net work done on the piano   J

  (a) Find the force required to give a helicopter of mass M an accelerwau1 ah4n6j (3e52ogz5fjbgpy dn x89ation of 0.10 g upw4dn2owx6pabyf3( j aeu5hng 8 j9g15zard.    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 t3 suulnchn;39he distance axis is linear and that $d_{\mathrm{A}}=10.0$ m and $d_{\mathrm{B}}=35.0$m. Estimate the work
done by force $F$ in moving a 2.80-kg object from $d_\mathrm{A}$ to $d_\mathrm{B}$   J

  The force on an object, acting along the x axithzu.5fscnkpr9n ol*x* f4(mdph2. pa/; u;g s, varies as shown in Fig. 6–37. Determine the wog;pu sr;/hl*a2nk (d 9 upxzop5.4f .cnt*fmhrk 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 particle a rppgyv zqq9a)+( z r-az.zb9s55-xatcts 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, c. ir jm prs56 .g5vi0vq*z)ycan oxygen molecule, 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 8*wtg, ymwx-w 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 stoty 7d*oz 548i)tbkur ;qsz yjg9xc o81p an electron $\left(m=9.11\times10^{-31}\mathrm{~kg}\right)$ which is moving with a speed of$1. 90\times 10^{6}\mathbf{m/ s}$ ? $\boxed{a\times10^{b} \mathrm{J}}$ a =    b =   

  How much work must be done to stop a 1250-kgcar traveling at 105kmk8gc;dga6w a*x/re7 q/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 /kzhj)4yd d3r 110 N on the arrow over a distance of 78 cm. What is the speed of d 3kjd/h r4z)ythe arrow as it leaves the bow?    m/s

  A baseball (m=140kg) traveling 32m/s movdr-qlvw twc2*f+qy6)k 27wot es a fielder’s glove backward 25 cm when the ball is caught. What was the average force exerted by the bq wto+kqf2rcv)y d67w 2t*lw -all on the glove?    N

If the speed of a car is increased by 50%, by what factor will j5.itlveln2. its minimum braking distance be increased, assuming all else is the same? Ignore the driver’s ln.t2lev 5j.ireaction time.

  At an accident scene on a level road, investigators measure a car’s skid mh v+ r0ic4+et9xmmh:kark 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 oniv9heh+m0t4: k m+rxc (and locked) the brakes. (Why does the car’s mass not matter?)    m/s

  A softball having a mass of 0tafpv / e3 8w+5i5gglk.25 kg is pitched at By the time it reaches the plate, it may have slowed by 10%. Neglecting gravity, gia5 5+ pf/kte3w v8glestimate 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 who doi- t k)b +b5uzm iwgr03*rv*rbes 80.0 J of work on it? Neglect air resistance.rztimbuvw ri **+ kb0-)35b rg    m

  A 285-kg load is lifted 22.0 m vertically with a 0:z4.mxefd jai+k kw9n acceleration by a single cable. Determinem4iz:.f 0d9awe kjkx+
(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 constant, k, of 440N/m How much mustb5kp m -d:bvcs8f6)fz this spring fd8fbz s :6)b5pk mc-vbe stretched to store 25 J of potential energy?    m

  A 7.0-kg monkey swings from one branch tpu m9qfr0);,7 hxd5- fop zvgqo another 1.2 m higher. What is the change in potential energy d,qm970; xog qfhur-)5pfvpz?    J

  By how much does the gravitational potential energy of a 64-kg po)1u(oldrsf5/ ylycw* le vaulter change if his center of mass rises about 4.0 m duringwydy1o5l/slr*)fc (u the jump?    J

  A 1200-kg car rolling on a horizontal sur)4jo6mg ek if:qbc0w,face 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 co)fmjki 6w0e q4 :b,gspring stiffness constant of the spring?    N/m

  A 1.60-m tall person lifts a 2.10-kpps:q f/y)0(l - naywkg book from the ground so it is 2.20 m above the ground. What is the potential energy ofp-yfwk sq:) 0 p/yaln( 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 rk, at w2)got0climbs to the top of a 3300-m )0,rtog w2akt peak.
(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 nex*i)x:ih kgrwe g 2o5(xt to a ruler. The end of the spring is next to the 15-cm mark on the ruler. I:)w g*rkxh2i( 5ixeogf 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 t7alax8) p1t-x 2nu wyxc/7 sfat top speed (5.3m/s) and grabs a vine hanging vertically from a tall 8xtl 2ftwa71 )xa/yx-nups7 c tree in the jungle. How high can she swing upward?    m
Does the length of the vine affect your answer? ----待选择----yesno 

  A novice skier, starting from rest, slides dow38 s(b.a kcmz6i6.g nbqc:w2 udm; mktn a frictionless 35.0$^{\circ}$ incline whose vertical height is 185 m. How fast is she going when she reaches the bottom?    m/s

  A sled is initially given a shove up a frictionless 2 ta.z gg 4-2lqw*3hiyxo27b lz8.0$^{\circ}$ 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 gravhc++ g) ctf8pritational potentir +cp h8ftcg)+al energy without the aid of a pole. With what minimum speed must Fran leave the ground in order to lift her center of mass 2.10 m and cross the bar with a speed of 0.7m/s.    m/s

  A 65-kg trampoline artist jumps vertically upward from the top of vx sz4* f*vink6 9l/fq w2u;ssa platform with a speed x 9vfq2issn6 wv;f*us/kzl *4of 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 (ignoreq 6dt8b)./rdwco9xx k its mass), whose spring stiffness constant is 950N/m is attached to a table and is compressed down 0.150 m. (a) What upward speed can it give to a 0 xw)dd 8kb 6roxtq.c/9.30-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 shown in youk c/b,x1nszx 6m/ (Fig. 6–39. If the block is to remain s,//xkm nbuzcyo1 6 x(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 attac3 ia7-7x.a7e xu kxawohed to the end of a spring (spring stiffness constant k), Fig. 6–40. The bliaa7xuk. 73oa xx-e7wock 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 whose;cjx ::azor ;hz9 v.au unstretched length is 12 m, and falls a total of 31 m. (a) Calculate the spring stifv.z:ao ; auczj h9;r:xfness 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 shhro y4u(ao +.sapa)5town in Fig. 6–41 is dragged up to point 1 where it is released from rest. Assuming no friction, calculate the speed at po aua5o4h+.ap)y( rtosints
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 anglejk - ;;hssevrgdj98bi(6wugx9i p:9f 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 ku;-*v/zb ys yrm/h+o placed at the bottom of an elevator shaft. If the elevator cable should break when the elevator is at a height h above the top of the spring, calculate the value that the spring stiffness constant k should have so that passengers undergo an acceleration of no more than 5.0 g when brought to rest. Let M be the *r/-u mso kbv;/z +yhytotal mass of the elevator and passengers.

  A cyclist intends to cyclow:/ een3j7uie up a 7.8 $^{\circ} $ hill whose vertical height is 150 m. Assuming the mass of bicycle plus cyclist is 75 kg,
(a) calculate how much work must be done against gravity.    J
(b) If each complete revolution of the pedals moves the bike 5.1 m along its path, calculate the average force that must be exerted on the pedals tangent to their circular path. Neglect work done by friction and other losses. The pedals turn in a circle of diameter 36 cm.    N

  Two railroad cars, each of mass 7650 kg and traveling 95km/h in oppos s ,;xr-rr g 4lp7i80w+y:8kc jsyfecpite directions, collide head-on a7ik s 8+eg8w;y cx:0l sr jprfp-r,yc4nd come to rest. How much thermal energy is produced in this collision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slide 3.5 m highhdi16t y;cby53r n/ sp and reaches the bottom with a speed of 2.2m/s How muchsbpyytr3 /d c5n;6h1i thermal energy due to friction was generated in this process?    J

  A ski starts from rest and sj:z9qo c9z g0nlides 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 fr4efv,opio y)g1 7.uiz om a tree 13.0 m above the ground.
(a) With what speed would it hit the ground if air resistance could be ignored?    m/s
(b) If it actually hits the ground with a speed of 8m/s what is the average force of air resistance exerted on it?    N

  You drop a ball from a height of 2.0 m, and it bou dpq*1qkrjf;d;d vakc .8vtni4z4 (h7 nces back to a height of 1.5 m.7q va;dqfi;k r4t 4kn8p.1 dh*djvzc(
(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, startihtj0bo747gh zng from rest, is pulled across a floor with a constant horizontal force of 350 N. For the first 15 m the floor is frictionless, and for the nextt0 jz h7hgb47o 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 1 with a speed of If the ;( fq 1sd+jzxyaverage force of friction is equal to one-fifth of its( +d yfsq;zxj1 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 stea d ght2s4lioa*8.z5 0hs 0wz /asysc-kdy 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 5 jyj0 u x76dc;a,6zbmvg kvkf d6xx)+spring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compressed 5.0 cm and released, stretches out 2.3 cm beyond the equilibrium posit amx; xbj 6d dv)jzc 6f,vkxu7kyg5+60ion 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 horizontal spring, Fig. .s :1pnqa5. 6sm dxiuu6–40. The block can slide along a table where t.5mpui: and1 xus6.sqhe 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 the s+ 2*d72zvhknjgn3v vm*lpyy +pace 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 landed at a speed of 200km/h (a) What would its landing speed have been i yvm+3yg j2nvdnl+ 2zp**h7kv n 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 e(5 krhir(j lo0z4xav+h.b( +b z 0lfbto a sixth-story window 16.0 m abo(a4.br(bx i+0k 0jovl5fhz(ez h+blr ve?    s

  If a car generates 18 hp when traveling at a sq5 4h5qf(yq5-fyyrui teady 88km/h what must be the average force exerted on the car due th5f(yqf5rqiq- uy5 y4o friction and air resistance?    N

  A 1400-kg sports car accelerates from rest to 95km/h g.9ha2 cglrf/oa .xy +x oor;1in 7.4 s. What is the averag2xo 1.f.oxayc;l/a9 gg+o rhre power delivered by the engine?$\approx$    hp

  (a) Show that one Br +i* qho reg 60wcfb.emjxx+/.itish 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 form of “kilowatt-hours.,vm c5 6ecvr0y”
(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,o . k7y0f/dv8ocy nqf 1150-kg car slows down from to 65km/h in about 6.0 s on the level when it is i7ofoyc8.vf/,d y0qk n n neutral. Approximately what power (watts and hp) is needed to keep the car traveling at a constant 75km/h.    hp

  How much work can a 3.0-hp motor dowg8e vcb )1u-xvg3jb4e7oz1zp 8ye jmq4 p) l6 in 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates a 7.3-kg shot from rest to 14m/s If this motion take bgqj:n9uj.yn/ /3ftns 1.5 s, what average p nf9qt.:nubgjjn 3/ y/ower was developed?$\approx$    W

  A pump is to lift 18.0 kg of water per minute through a height of 3. wy2)xb cug+n m.mze-460 m. What output ra) 2 g+zuycbm.4e n-wxmting (watts) should the pump motor have?    W

  During a workout, the football players at Statutbam.ur ;n7 t8y;) jqe U. ran up the stadium stairs in 66 s. The stairs are 140 m long and inclined at an angle of 32 a u.rm; njquyt8;b)7 t$^{\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 cycliih/rs+gr )n3k st climb a 6.0 $^{\circ} $ hill to maintain a power output of 0.25 hp? Neglect work done by friction, and assume the mass of cyclist plus bicycle is 68 kg.   m/s

  A 1200-kg car has a maximum power output of 120 hqt2pm)qz9 vq:, 9znzvp. How steep a hill can it climb at a constant speed of 75km/h if the frictional forces add up to 650 z9qpvn :9,z z)q2qmtv N?    $^{\circ} $

  What minimum horsepower must a motor have to be a4r2rmmqger, t/d 2.j3dmr3 e 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,ee a2 m2r33m./r4trmgrdqdj .45?    hp

  A bicyclist coasts do i(1(dcowpv( 6;yt: oz9quap8ulkc,xwn 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 desi3*mbe(tnjb9 e gats(0ix fd31 gned to compress and rebo xa0b g3n9e*de 3st(mtfbj(1i und elastically without any physical damage at speeds below 8km/h If the material of the bumpers permanently deforms after a compression of 1.5 cm, but remains like an elastic spring up to that point, what must the effective spring stiffness constant of the bumper be, assuming the car has a 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 9cf7ox q;8 v6yd+q omhfirst shelf is 10.0 cm off the ground, and the remaining four shelmocf9hq;od7q 6 yx+v8ves are each spaced 30.0 cm above the previous one. If the average book has a mass of 1.5 kg with a height of 21 cm, and an average shelf holds 25 books, how much work is required to fill all the shelves, assuming the books are all laying flat on the floor to start? $\approx$    J

  A film of Jesse Owens’s famous long jump (Fig. 6–4t2z i7z3)vht,5 vv gtw2) in the 1936 Olympics shows zgv7)3 wtiztv 52t,vhthat his 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 friction along the looped track shown in Fiwy+zl ox (j0 ehw;9pi(g. 6–39 is to remain on typ+o9iz(0(w e h lxw;jhe 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 without his para9hp2b8cf7q6t h2l zfjchute 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 estimattlc 7z2fbp8h2q6hjf 9e
(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 enb 5dvug-dwnfg95 fbv2/c 5g *yd is fixed (Fig. 6–4*ndy - dbgcvf59uv/g 2 g5wfb53).
(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 thei i cx,;6e0 (ch+mhfgz top of a 3700-m-high mountain. The climb is made in 5.0 h starting at an elevati+ef6z i;hx gc(,cmh0i on 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 wh 8eb * 5hkq,kzdrg:b(uen a 920-kg elevator is 28 m above a huge spring ($k=2.2\times10^{5} \mathrm{N/m}$) at the bottom of the shaft. Calculate
(a) the work done by gravity on the elevator before it hits the spring,$\approx$    j
(b) the speed of the elevator just before striking the spring,$\approx$    m/s
(c) the amount the spring compresses (note that work is done by both the spring and gravity in this part).    m

  Squaw Valley ski area in California claims that its lifts can move 47,000 p bf*l g w.xrmez(d)*+teople per hour. If the average lift carriesf d.b *(*+zgl)xmrwte people about 200 m (vertically) higher, estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dapnk5g+ek k o.tr90i2zm at the rate of 650kg/s and falls vertically 81 m before striking the turbinn 5kgt z90i2rok. +epke blades. Calculate
(a) the speed of the water just before striking the turbine blades (neglect air resistance), $\approx$    m/s
(b) the rate at which mechanical energy is transferred to the turbine blades, assuming 58% efficiency.    W

  Show that on a roller coaster with a circular vertical loonvkt -+yswnc1xmuis /4c8u z0ff 7)+pp (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. st) cs-+if cxuk nm+4wp f0y/17 v8uznIgnore 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 bo w wi;lqzdw +o;id/yl )7)vn/yil0(v7 4bddgar directly into work, how high could an 82-kg man climb a ;yqlwv wo0l/)/7(i+o 7dwb)4;idnzldgdvy iladder 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 ym0a1 ) stfjo/e7 4xczat an upward angle of 45.0$^{\circ} $ from the top of a 165-m cliff with a speed of 175m/s What will be its speed when it strikes the ground below? (Use conservation of energy and neglect air resistance.)    m/s

  If you stand on a bathroom scale, the spring inside the scale compresseyv.sj18iq3 3d ww, knhs 0.60 mm, and it tells you your weight is 710 N hww3kn.qsd3 i,vjy81 . Now if you jump on the scale from a height of 1.0 m, what does the scale read at its peak?    N

  A 65-kg student runs at 5m/s grabs a rope, and swings ou4r-2) (tnryhr amr57czm qkmb6 0:y mrt over a lake (Fig. 6–45). Her(4hmq2r k- )5r:ba0ncy trm7yzm 6mr releases the rope when his velocity is zero.
(a) What is the angle when he releases the rope?    $^{\circ} $
(b) What is the tension in the rope just before he releases it?    N
(c) What is the maximum tension in the rope?    N

  In the rope climb, a 72-kg athlete climbs a vertical distance of 5.0 m iaimn)g w . f4b618 dbyy45sikon 9.0 s. o i86sfk)4b1g dn4b 5.ymwiyaWhat minimum power output was used to accomplish this feat?    W

  Some electric-power companies use water to sto bmx/numg0t-bl7 iqvx2 55 qi6re energy. Water is pumped by reversible turbine pumps from a low to a high reservoir. To store the energy produced in 1.0 hour by2t/iuq x nb g5xiqmlm-705vb6 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. What is the sdl e.7n*ur0mlpring stiffness constant for each of the two resulting spri.*ld 0nl ru7mengs?   k

  A 6.0-kg block is pus7p vc,ibkl81wppuyb49eb q3 ,hed 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 t uwkz+curh5+ t wwo,,.o 55km/h in 3.2 s, how long will it take to accelerkt+wr,w .+z w5uu,choate from 55km/h to 75km/h Assume the power stays the same, and neglect frictional losses.    s

  In a common test for cardiac fue,;/hi(vuy p ld.i1 rbnction (the “stress test”), the patient walks on an inclined treadmill (Fig. 6–46). Estimate the power required from a 75-kg patient when the treadmipieb/v1;,.rulhyd( ill 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 upwa5 .wnqmv or m3w52e*bard a distance of 500 m, what was its vm 5mn23b 5qar. wev*owelocity when 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 wat - s w4y0xkehqeai+u(+er wheel from a height of 2.0 m at a rate of 95kg/s (a) If this water wheel is set up to provide electricity output, what is its max4w siu eqa+(y k0hxe-+imum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s