In what ways is the word “work” as used in everyday language tf j/u.*h p-4mufal3u7 dzz me0he same as that defined fj.u 403zzmua 7md/e-*f luhpin physics? In what ways is it different? Give examples of both.

Can a centripetal force ever do work 0/)7egjuh8ev kt d11z +kbew:y myv1j on an object? Explain.

Can the normal force on an object e -qt;gjs9,bvd6opt9 ever do work? Explain.

A woman swimming upstream is not moving with respect to thhz jff55md eve/ 9k-uh2n 9s2te shore. Is she doing any work? If she stops swimming and merely floats/95k5dzmn 2- ff9h vh u2jeset, is work done on her?

Is the work done by kinetic friction forces y(p:m uz1er ,ealways negative? [Hint: Consider what happens to the:z(, rypeem1u dishes when you pull a tablecloth out from under them.]

Why is it tiring to push hard agaidfj3*g4obt6no :s s70k lpfh;d+c 1g jnst a solid wall even though you are doing no c*6 :gofdgdtfssn3h1+jl ;ok7 bp 04jwork?

You have two springs that are identical except that spring l op pkhh 9,d4anm2+l0wis stiffer than sprind+kn92 homp hp4l, wa0g 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,4vqxy0p2tj71s kc bi 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 tr0c7sivt2q 4kjy1 x b,paveled a distance $d$ to point B it is traveling withe bint $o$ point B it is traveling with speed $\nu_\mathrm{B}$.When the block has traveled another distance $d$ to point C, will its speed be greater than, less than, or equal to 2$\nu_\mathrm{B}$? Explain your reasoning

By approximately how much does your gravitational potential ene .gnvwo,7;:amlmtx sm3a- .q yrgy change when you j a,;vmqam .3s7noytgx-w :ml.ump as high as you can?

In Fig. 6–31, water vb3nk6:9h fl/ jwryh9 balloons are tossed from the roof of a building, all with the same speed but with different launch angles. Which one has thln3v9 f:h/h w 6kr9jbye highest speed on impact? Ignore air resistance.

A pendulum is launched from a point that is a height h above its lowes*gf p.:roi9r;w 6ag kiz*y pw)t point in two different ways (Fig. 6–32). During both launches, the pendulum is given an initial speed of 3.0m/s On the first launch, the initial velocity of the pendulum is directed upward along the trajectory, and on the second launch it is directed downward along the trajectory. Which launch will cause it to swing the largest angle from the equilibrr6a:z )y.wrp gwgi*f9 *pi;koium position? Explain.

A coil spring of mass m rests upright on a tab a4 256ihobvwdle. If you compress the spring by pressing down with your hand and then release it, can the spring leave the table? Explain, using the law of conservationiavd5 4w 2o6hb of energy.

A bowling ball is hung from the ceiling by a steel wire (Fig. 6–33). The instr-flq-a6 af6i-tnwb5 luctor pulls the ball back and stands against the wall with the ball against his nose. To avoid injury the instructor is supposed to release the ball w6af6 -btifnawql 5--lithout pushing it. Why?

What happens to the gra79c y((j1d wg-ghn hobvitational potential energy when water at the top of a waterfall7 ow -gh 1n9gcbyhdj(( falls to the pool below?

Describe the energy transformations when4el1 -sd ee)ri a child hops around on a pogo stick.

Describe the energy transformations ta;si j o0o(la 4dhn64nhat take place when a skier starts skiing down a hill, bu0o jn4o 6 (dhas;4inalt after a time is brought to rest by striking a snowdrift.

A child on a sled (total mass m) stat4wrf7ikg;* vr5*pf( n 9td qjexau o6(c(0rtrts 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 hicxtv(n*fte 6(prr( uf w *toj d 74qakg;095rill if (a) it is icy and there is no friction, and (b) there is friction (deep snow)?

Seasoned hikers prefer to step over a fallen log in their path rather thw +r dlurq7f)0h rp,f(an stepping on top and jum ,70)(dfuwrlrr q fph+ping down on the other side. Explain.

Two identical arrows, one with p1 t nqw8*)pcgtwice the speed of the other, are fired into a bale of hay. A p8pqn)* 1wtcgssuming the hay exerts a constant frictional force on the arrows, the faster arrow will penetrate how much farther than the slower arrow? Explain.

Analyze the motion of a simple swinging pendulum in terms of energy, (a) ignorin7,s 9h5+8mkp m)nizw c69riy q mck6pdg friction, and (b) taking fric+cqdkm wc9p) p9i7s5y68mnzk ,6i r hmtion into account. Explain why a grandfather clock has to be wound up.

When a “superball” is dropped, can it rebound to a heighwqcxu;a0178 gd grno.t greater than its original height?adxw. ru80 cg7q no;1g Explain.

Suppose you lift a suitcase from the floor to a tn743 ,,goeag/zxw d3ewvezt -able. The work you do on the suitcase depends on which of the following: (a) whether you lift it straight upz3 n/evt , wgede-3xoz g74w,a 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 the power needed rathejb ubajjn7j m3s6. e94r than the work.

Why is it easier to climb a mountain via a zigzagx.w rcsuywkg 0*)(k8l trail than to climb straight ukkgs 0u wcxw.l ry*8)(p?

Recall from Chapter 4, Example 4–14, that you can use a pulley and ropes to decr h4+12n6 g gzfck8 cttccd t/rec4hj*)ease the force needed to raise a heavy load (see Fig. 6–34). But for every meter the load is raised, how much rope must be pullj c21/ ht6tdcg e)h*8cgrf c4cntz+k4ed up? Account for this, using energy concepts.

  How much work is done by thayim q;pu*u3gk8na:k2q 5c v;e gravitational force when a 265-kg pile driver falls 2.80 mv 8y3: p ;nk*uu;c a5mi2kqaqg?    J

  A 65.0-kg firefighter climbs a flight of stairs 20.0 m high. How muchtdy+6ff 7: dhx work is required?76d:d+xythff    J

  A 1300-N crate rests on the floor. How much work9om. g8e,ob rn is required to move it at constant speed (a) 4.0 m along the floor against a friction forc,go .obmen9r8e of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers9cqeqf.v,dy fh7.w 5w do (horizontally) pushing a 160-kg crate 10.3 m across a rough floor without acceleration, if the effective coefficient of friction was 0.50?qq.df e9vwfwy.7h 5c,    J

  A box of mass 5.0 kg is accelerated by a force across a floor at a rate ofrv91e 5e3l aoy for 7.0 s. Find the r3eo9ylaev51 net work done on the box.   J

  Eight books, each 4.3 cm thick with mass yu4-ogp bm:t g846t)xnb) bo b1.7 kg, lie flat on a table. How much work is required to stack them4o pxtbg ny :)bob8gmb4-)u6t one on top of another?    J

A lever such as that shown in Fig. 6-35 can be used to liff objects we migh (28)3wttyv xjuzxmc3t not oth x8jwcyt )umzxt32v(3 erwise 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 accelerating by ofc4*f0hy-p qa man who is pushing back on it parallel to the incline (Fig. 6-36). The effective coefficient of kinetic frict4fyfp hoc*q-0 ion 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 accelexod+b * 5ij0k lfknhf*-*u8kuration of 0.10 g u+j-*fk*k*08xfhdnibku5 ol 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 x9mbf:.v9d qtej9lx/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 sg79 62-pgsb m0wbswh axis, varies as shown in Fig. 6–37. Determine the s2wbm7g9 06bsph -gws 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 particle acthzyxcx) u3je, mbe5ke; )y73l s in the $+x$ direction. Its magnitude increases linearly from zero at
$x=0$, to 24.0 N at $x=3.0$ m. It remains constant at 24.0 N from $x=3.0$ m and then decreases
linearly to zero at $x=13.0$m. Determine the work done to move the particle from $x=0$ to $x=13.0$ m
graphically by determining the area under the $F_x$ vs. $x$ graph    J

  At room temperature, an oxygen molecule, with mass oymm18t.x)j o q gr gut:ru(31yf $5.31\times10^{-26}$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 spx7lt)u6+ gjo veed increased? $ \sqrt{a}$ a =    (b) If its speed is doubled, by what factor does its KE increase?   

  How much work is requireqptsb7p2 l ujpk533g l) kv..rd to stop 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-kj,zt:;n vuas) gcar traveling at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whosejca 2ccgx, /wdguwmm+38/u5 5 kg5ia y string exerts an average force of 110 N on the arrow over a distance of 78 c/jkuc5 i5a853 acgx,gm w dgu+w /ymc2m. What is the speed of the arrow as it leaves the bow?    m/s

  A baseball (m=140kg) traveling 32m/s moves a fielder’s glove backwo /9c5z rjmml-ard 25 cm when the ball is caught. What was the average force exerted j5m9/ orl-mcz by the ball on the glove?    N

If the speed of a car is increased by 50%, by wql(phma 6((xx,ps + uehat factor will its minimum braking distance be increased, assuming all else is the same? Ignor se (lhq6x(+, uxamp(pe the driver’s reaction time.

  At an accident scene on a ledq60y vp k8zhr d0cy*c-*+z+xnux. znvel road, investigators measure a car’s skid mark to be 88 m long. The accident occurred on a rainy day, and the coefficient of kinetic friction was estimated to be 0.42. Use these data to determine the speed of the car when thy.+d*n0nx6dc-yz*8vc h x0 k rp uqz+ze 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 p 6og nlcpt-m wd4w)q5 cl.+.lkq-t4 oxitched at By the time it reaches the plate, it may have slowed by 10%. Neglecting gravity, estimate the average fo4. lw4qoctc mknp+t lgo-6x5) .-q lwdrce 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 av+s/0 ypzmc1 straight up by someone who does 80.0 J of wo1a0+cm /pys vzrk on it? Neglect air resistance.    m

  A 285-kg load is lifted 22.0 m vertically with an acceleratioe29 b;w.ct1 j -h 7v-dhog7tny-*d5djknehozn by a single cable. Detet;eh zjnt5h 7 -oecyn.j2ob h vwd19*kgdd-7-rmine
(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 constatd*frq 5o4igmm iz(* +nt, k, of 440N/m How much must this spring be stret i4r5** qtimf+ dz(gomched to store 25 J of potential energy?    m

  A 7.0-kg monkey swings kj1*g)x83 .ngfu .mk p.u 4p5 crkourofrom one branch to another 1.2 m higher. What is the change in potential en kj)p.5 pocrxk3gnu* guk1o4fmr. u8.ergy?    J

  By how much does the gravitational potential energy of a 64-kg+8ijyns mn,/ t pole vaulter change if his center of mass rises about 4.0 m during the jum+nsijm /t,n y8p?    J

  A 1200-kg car rolling on a horizontal surface has speed v = 65 km/h when iluwo8,f7dp3npzzl / ( 0tg ;azt strikes a horizontal coiled spring and is brought to rezgd,8 pt w0 on z7ap3uz;/lfl(st 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 from the ground so it is 2.20rep dy/1.0+fhw czb rjgt/ k90 m above the ground. What9pdr0 rzhjfec+./ t/1 yb0gwk 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 owt:xtg7*6 mjjha:dp ; :sl3q)jls vp(f 1600 m and climbs to the top of a 3300-m peak. sl* s)vdtptg j:7mq(xwl; p36j::ja h
(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/mz9 kv id b dt69og)(cm*0abym7 hangs vertically next to a ruler. The end of the spring is next to the 15-cm mark on the ruler. If a 2.5-kg mass is now attached to the end of the spring, where will thb9 bdi 69c)mt0z dvo(7kamy*ge end of the spring line up with the ruler marks?    cm

  Jane, looking for Tarzantd: nu1ey db2d r-s65r (+ lto9scjc8mjr 9b;a, is running at top speed (5.3m/s) and grabs a vine hanging vertically from a tall tree in the jungle. How hi b8dyb+j et: l;ntj9s r61cmar25(c9dds-our gh can she swing upward?    m
Does the length of the vine affect your answer? ----待选择----yesno 

  A novice skier, starting from rest, slides down a frictionless 35h9 :)5h huhxeo.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 shogva p7, li7 +t/f ujaajy**.cwve up a frictionless 28.0$^{\circ}$ incline. It reaches a maximum vertical height 1.35 m higher than where it started. What was its initial speed?    m/s

  In the high jump, Fran’s kinetic energy i/62la9v6u c/wew zv p)luo.o ds transformed into gravitational potential energy 6cpea9 wv vlz6)d//u2.o wlou 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 jumpsp- pmam nx.xp:gk :3s6 vertically upward from the top of a platform with:6.pnksx m-3p a pmx:g a 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 stizzy idp( d6)hp**lp7f ffness constant is 950N/m is attached to *6p(f d7pzl*d)hip yz a table and is compressed down 0.150 m. (a) What upward speed can it give to a 0.30-kg ball when released?    m/s
(b) How high above its original position (spring compressed) will the ball fly?    m

  A block of mass m slides without friction along the looped track shown in F:h*.tlu s6inb ig. 6–39. If the block is to remain on thei6 nlh:t s.b*u 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 r3b5z/ g gtct5spring (spring stiffness constant k), Fig. 6–40. The block is givczg/tb5t 5g 3ren 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 tjhjexe 0 0)yv:c9 yza6ied to a bungee cord whose unstretched length is 12 m, and falls a total of 31 m. (a) Calculate the z0a0c:e jy6e xvh)jy9 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 up to point 1 where i) ahbzdd,(* 7 jefdr5wt is released from rest. Assuming no friction, calculazd,5) w( b rjdha7e*fdte the speed at points
2    m/s
3    m/s
4    m/s

  A 0.40-kg ball is thrown w(iz 4bud 3yv-*mphv(0 *cdybqith a speed of 12 m/s at an angle of 33 $^{\circ} $. (a) What is its speed at its highest point    m/s
(b) how high does it go? (Use conservation of energy, and ignore air resistance.)   m

An engineer is designing a spring to be placed at theh4pkd/ toz3:ml b2arbv5,si 3 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 passengkah:m35s2i3d4vpbl/bo z t r ,ers 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 uplks x5yr.8s5c 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 o ko478u2cqqd3cenpgput 6x s k4,02 dyf mass 7650 kg and traveling 95km/h in opposite directions, collide head-on and come to rest. How mo4ck 2kcpg p0d8s24uex6 y,q7t3d nq uuch thermal energy is produced in this collision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descg z,76rwd iaw8ends a slide 3.5 m high and reaches the bottom with a speed of 2.2m/s How m,z8 irwwd6 7aguch thermal energy due to friction was generated in this process?    J

  A ski starts from rest and slidix )rqa;o;u t3es 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 n gcg;5vb/cz4.0 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 it3usrzv bba;; p ,.t9cn bounces back to a height of 1.5 m. r ;psnv3c9u.bat b,;z
(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 with z 6rarwbc+t/pp-65y q a constant horizontal force of 350 N. For the first zty-66pr c r5wa p/q+b15 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 coaster in Fig. 6–41 passes point 1 with a b he, cj ml +/qmkh-,erf-0f4jspeed of If the average force of friction is equal to one-fifth of its weight, with what speed will it reach point 2? The distance travelfc,fj -m /m,hkb0rej4 lhe- +qed is 45.0 m. $\approx$    m/s

  A skier traveling 12m/s reac46 8j-z5gy pjk4 1ohasku*r r:zl x)snhes the foot of a steady upward 18.0 $^{\circ} $ incline and glides 12.2 m up along this slope before coming to rest. What was the average coefficient of friction?   

  A 0.620-kg wood block is firmly attached to a very ligy3 ( t.2uu yb(ufwaw(doyk1*xht horizontal spring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compresseb w2 utyyxwu(ody* .1a(3ufk( d 5.0 cm 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 att8pn;o ft(z;fyyy9 jg7ached to a very 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, how far beyond its equilibrium position will it stretch on its first sp o;yzgn 9;8(fyyjf7 twing?    m

  Early test flights for the space shuttle used aszoy,6 idx; y,awvu.9:ivd/c “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 dawi9v ,us,zd.i:oycv/xy; 6 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 piay0w x) p:zrk3tno to a sixth-story window 16xpzkt)r w0y3: .0 m above?    s

  If a car generates 18 hp when traveling at a steady 88km/h what must be.)5eo,hz .o g655 jigjdri3 0nncsk o+kwpo0w the average force exerted on the car due to frictr.ojw6o5nk w+3.h5d,50)icnpo kgizs 0je goion and air resistance?    N

  A 1400-kg sports car accelerates from restufex yfs *a12r** wty, to 95km/h in 7.4 s. What is the average power delivered by the engine?1w y *seur ,*a2tyx*ff$\approx$    hp

  (a) Show that one British horseri8ffwn (,uwv d8o6; pq83 qvppower$ \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 o 3 pd6j;fm1/ zdwm5a k8rq;w:1qg try+fonv-eften expressed in the form of “kilowatt-hours.”
(a) Show that one kilowatt-hour (kWh) is equal to $3.6\times10^6$J
(b) If a typical family of four uses electric energy at an average rate of 520 W, how many kWh would their electric bill be for one month $\approx$   kW*h
(c) how many joules would this be?$a\times10^b$ J a =    b =   
(d) At a cost of 0.12 dollars per kWh, what would their monthly bill be in dollars? Does the monthly bill depend on the rate at which they use the electric energy?    dollars

  A driver notices that her 1150-kg 9vpu*l s+o34gv k4bmv*0 qdxt car slows down from to 65km/h in about 6.0 s on the levelqdvsgp9lm+403v b4t* *kox uv when it is in 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 do in 1.0 h? s+gfkgmo7*5gw34+af ast(x 9ftfy4 z$a\times10^b$ J a =    b =   

  A shot-putter accelerates a 7.3-kg shot from rest to 14m/s If this motiozp53 uia*mz1gn takes 1.5 s, what average power was p51gm z3az u*ideveloped?$\approx$    W

  A pump is to lift 18.0ep3t1zn4y1legq 9 cg: kg of water per minute through a height of 3.60 m. What output rating (watts) shoulqn1pg:g y19ce43ztl ed the pump motor have?    W

  During a workout, tho:.leog) v8 +sinv9 nbe football players at State U. ran up the stadium stairs in 66 s. The sta.+svieg n: o8b)lnv o9irs are 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 cyclistgrvn;3fz 8: oz 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 r07 +6fdidjx g3qmwl6output of 120 hp. How steep a hill can it climb at 3lm6 rq6g0ix w jd7fd+a 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 zm34tsge7e -t to drag a 310-kg box along a level floo-g7tesmzte34 r at a speed of 1.2m/s if the coefficient of friction is 0.45?    hp

  A bicyclist coasts down a o134ajc ;rpm (v owpw9 k/phh,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” 2yi, sws7:s(crm ,q w;r azas,that are designed to issmsa:,( qs,rya;, 7wz2r cwcompress and rebound elastically without any physical damage at speeds below 8km/h If the material of the bumpers permanently deforms after a compression of 1.5 cm, but remains like an elastic spring up to that point, what must the effective spring stiffness constant of the bumper be, assuming the car has a 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 10.0jt y+y2:h c.qw 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 the books are all laying y: wtj+q.2cyhflat on the floor to start? $\approx$    J

  A film of Jesse Owens’s famous lajgs e g)eou 4-- c,s/b::gyozong jump (Fig. 6–42) in the 1936 Olympics shows that his center of mass rose 1.1 m from launch point touso -e s z:gc),-b:ay4ejgg/o 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 shn)d9 zab kgz+/own in Fig. 6–39 is to remain on the track at all times, even at the very top of the loop of radigad/bzk 9+)z nus 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 pz7sd q 0omp of0l;7l3carachute opening. He landed in a snowbank, creating a crater 1.1 m deep, but survived with only min lzops0 3 ;0lofqcmd77or 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 eni:pzp5o ;e wq/5bjj5rd is fixed (Fig. 6–43)j j/iepqrb55:zpw ;5o.
(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.m0edw7owg9 o,erz; y top of a 3700-m-high mountain. The climb is made in 5.0 h starting at an7deo ,w; 0g9.rywezmo 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 above a huge spx)dh+/;9huu b ) etyakring ($k=2.2\times10^{5} \mathrm{N/m}$) 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 Californiat-/n.xzf*k bmoud */h claims that its lifts can move 47,000 people per hour. If the average lift carries people about 200 m (vert**.ztm ofu-/nxdkb/ h ically) higher, estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam at the rate of 650kgq j:id(q,h-am/s and falls vertically 81 m before striking thei:haq,(mdq -j 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 with a circular vertical loop (Fig. 6–44), the t8t 1k.lh9rj8 ) gih5tamdae9difference 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 thr9httm1a5htl9 j8 e. gi)da8k e 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 cwwh/7 w:fn86neukh, 2d zxw6aj;y0sconvert a candy bar directly into work, how high could an 82-kg man climb a ladder if he were fueled by one2 nw6 hhy6 fewxa0wjkw,c/ dn s;:8z7u bar (=1000kJ)    m
(b) If the man then jumped off the ladder, what will be his speed when he reaches the bottom?    m/s

  A projectile is fired at an upwarocor3 dy d-)7pd 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 innha5 xpget )dnce ;g::wsf6q4l pbm 50z5u 0-qside the scale compresses 0.60 mm,m5zq:)0pah;lw6 5bexsg -nfcg5pqnd4: 0e ut and it tells you your weight is 710 N. Now if you jump on the scale from a height of 1.0 m, what does the scale read at its peak?    N

  A 65-kg student runs at 5m/s grabs a rope, and swing8 zv8b 25v+vz*xc;noki uz *las out over a lake (Fig. 6–45). He releases the rope when his velocity is zero+5n k8bivz; vc*lzou2x * az8v.
(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 distanceav51 hoe9nl o. of 5.0 m in 9.0 s. What minimum power output was usav1 e 9no5hlo.ed to accomplish this feat?    W

  Some electric-power companies use water to store energy. Water is pumped by rn512h i kuo8dieversible turbine pumps from a low to a highu21koii h8dn5 reservoir. To 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. What -0x.ynera8)nb8cg wgvt.d q: is the spring stiffness constant for each of the two resulting s-d )x8.e8wb: qt0yvacnr.n ggprings?   k

  A 6.0-kg block is pushed 8.0 mrmjthz 82tox26qa 4i ip6vi87 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 frv9h pvl l-uu*s)1 0lmrom 35km/h to 55km/h in 3.2 s, how long will it take tov*llp)muvsr 109l h -u accelerate from 55km/h to 75km/h Assume the power stays the same, and neglect frictional losses.    s

  In a common test for cardiac functu4pr9hw78n acu m,.ayion (the “stress test”), the patient walks on an inclined treadmill (Fig. 6–46). w9y78uc a,ar4.npmhu Estimate the power required from a 75-kg patient when the treadmill is sloping at an angle of 15 $^{\circ} $ and the velocity is 3.3km/h (How does this power compare to the power rating of a light bulb?)$\approx$    W

  (a) If a volcano spews a 500-kg rock vertically upward a dista36o/ +ip8hjgxuiog.e nce of 500 m, what was its velocity wheiho8 / x +6og.3ieupgjn 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 sq +r;ecjt0qt mn. bt4+9r;o n5n vyk)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 maxi m0+je9nnr nbqcy )o+tv;;tkst5. q 4rmum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s