In what ways is the word “work” as used in everyday language the same as that d- pyd-kw3 rv ki .j6i1zar ;vc53jv:lbefined in physics? In what ways is it different? Give exam;vb rd.v: cjk15ywl-avp-rz3ij6k i3 ples of both.

Can a centripetal force ever dosffje7kdm2/kk2 0 z-t work on an object? Explain.

Can the normal force on sb8wi2- va*qu* dk wt(an object ever do work? Explain.

A woman swimming upstream is not moving with respect to th 2 1vebi8jo+pabd4p.7 bs pi:ve shore. Is she doing any work? d14pi 2is bp b7b+:voj8v.peaIf she stops swimming and merely floats, is work done on her?

Is the work done by kinetic frb6h u/o9*tw coiction forces always negative? [Hint: Consider what happens to the dishes when you pull a tableclw*ht/oo b9cu 6oth out from under them.]

Why is it tiring to push hard against a solid wall even though you are doing n uxwpg(:xli8* o wo(glxu wxip:*8rk?

You have two springs thate;fri3c t63hy are identical except that spring l is stiffer than spring ceh r fi3t36;y2 $(k_1>k_2).$ 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 constanx8 nkve6 +1qvct horizontal force on a block that is free to slide on a frictionless surface (Figv v1e+x6 cqn8k.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 gravitatip)axtlg759krh7py8 7 rh uxc7onal potential energy change when you jump as high as you can?upy 7crar x7lpk857 9 thg7x)h

In Fig. 6–31, water balloons are 2 d2 w( +derj. sc kim/+2xvvuf02fzkbtossed from the roof of a building, all with the same speed but with different launch angles. Which one has the highest speed o+ijf dfbd(vkv.2sr +uxe20 /2 k2 zmcwn impact? Ignore air resistance.

A pendulum is launched from dz5*g(e 1pea1:erudk a point 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 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 g p5dk :e*(du1e ae1zrthe equilibrium position? Explain.

A coil spring of mass m rests upright on a table. If you comj( 5*n .n,z aymfdmfnj9 t4c k h):jo+5phs,mjpress the spring by pressing down with your hand and then a9*fc55ozhfd k4:.jj+m js )(y,t,hmpjnnm n release it, can the spring leave the table? Explain, using the law of conservation of energy.

A bowling ball is hung from the ceiling by a steel wire (Fig. r)rmyf6t /gzujr ecpo230o* p m 78c0a6–33). The instructor pulls the ball back and stands against the wall with the ball against his nose. To avoid injury the instructor is supposed to2m70 u0m)po *g fr6cepcz /jr 3t8aory release the ball without pushing it. Why?

What happens to the gravitational potential energy when /8vw/ ozqji(*kz srv.water at the top of a waterfall falls to the pool be8/zv .orzw(*v/sj qik low?

Describe the energy transformations when a child hops around on a pogo sga p2vkz6 -vy,tick.

Describe the energy transformations l 8m gi2g/8xgt mb,3xzthat take place when a skier starts skiing down a hill, but after a time is brought to rest by striki gxibtx8,28mm3zg /lgng a snowdrift.

A child on a sled (tot4t k: w;k4m ntatnddhi7.as4e,+vy+kal mass m) starts from rest at the top of a hill of height h and slides down. Does the velocity at the bottom depend on the angle of the hill if (a) it is icy and there i ;w shnv,tndkya atmk:+74d+i.e4 t4ks no friction, and (b) there is friction (deep snow)?

Seasoned hikers prefer to step over a fallen log in their path rather tha80hpdg)oedut2 yw3m* 94v z5ps z c/cqn stepping on top and jumping down on the other side. Explain. ghzudt4yc )/p2 q0wp8v9e5m3d *sozc

Two identical arrows, one with twice the speed (b mp0t*nzgu8i;bsu- hzq elu3(0q,b of the other, are fired into a bale of hay. Assuming the hay exerts a constant frictional force on the arrows, the faster arrow w znuql0,b*sbemz- 03u b( ;i hgtqu(8pill penetrate how much farther than the slower arrow? Explain.

Analyze the motion of a simple swi (um*v0t;z wdonging pendulum in terms of energy, (a) ignoring friction, and (b) taking friction d( *vtw 0zu;ominto account. Explain why a grandfather clock has to be wound up.

When a “superball” is dropped, can it rebound to hsq v0z0-rg,cb*us3z2iv p w-a )r n7ta height greater than its original height? Expla0z ph0, iqsg s2 7-rz- 3*waurc)vvbntin.

Suppose you lift a suitcasn 2;xog2z ve0o6v-r tne from the floor to a table. The work you do on the suitcase depends on- o0n2novgrtz6 xev2; which of the following: (a) whether you lift it straight up or along a more complicated path, (b) the time it takes, (c) the height of the table, and (d) the weight of the suitcase?

Repeat Question 22 for the power needed rather thanrc /rfevs0 r/9aix3:oy ed5n8 the work.

Why is it easier to climb a mountain via a zigzag trail than tmyo3rr amr(ggz( s*q01f6w4y o climb straight uygo36 as fmg4yr z*rm(q01 w(rp?

Recall from Chapter 4, Example 4–14, that you can use a pulley andfv e;f*gj9 svmizi(i,ohm88xq 4. rce.kn; 7 r ropes to decrease the force needed to raise a heavy load (see Fig. 6–34). But for every meter the load is raised, how much rope must be pulled up? Accounes9fj8g r7. q mxz,f8*;.cirvk;meh oi(4nvit for this, using energy concepts.

  How much work is done by the gravitational force when a 265-kg pile drive8c5qei0 0qyo k 9ty.a56dpgin r falls 2.80 k09 ciqo5 8edq.n a5p 0gyyt6im?    J

  A 65.0-kg firefighter climbs a flight of stairs 250ti e:vhvt0d0.0 m high. How much work is required?id 50 e0vthvt:    J

  A 1300-N crate rests on the floo1 g . e-,wxxlr4kye72nn5 rdnxy6jo(h r. How much work is required to move it at constant speed (a) 4.0 m along the floor against a friction forc ygnyxe.,j-drn6weo 4(hr5n k17xlx 2 e of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (horizontally) pushing a 160-kg cratr5j9zex64 ok re 10.3 m across a rough floor without acceleration, if the effective coefficient of fricter56x9j ok rz4ion was 0.50?    J

  A box of mass 5.0 kg is accelerated by i v;g rgdu4s-- ger)1aw9o4y6 usf3 cla force across a floor at a rate of for 7.0 s. Find the net work done on the)fye-a w31ios ds 494-g guu cg6r;rvl box.   J

  Eight books, each 4.3-3n1aqqx c;c k cm thick with mass 1.7 kg, lie flat on a table. How much work is required to stack them one on top of another?kca-qc;31n xq    J

A lever such as that s xw99gduw /g-uhown in Fig. 6-35 can be used to liff objects we might not otherwise be able to liff. Show that the ratio of outputxd9uww-/9ugg 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 ans vyml;wku8/wm rrx 8h/;)* npd is kept from accelerating by a man who is pushing back on it parallel to the incline (Fig. 6-36). Ther* w )m ;w/m8suhvl;k/8rnypx 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 accelerat/ffo4q1s..fbu g0 z mtion of 0.10 g upwa4f1gt./qfu m s.0b fzord.    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, assumeb 8x:u-g;a mbyjo y5/c the 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 axis ,qdk58 g ihtc(1d6oot, varies as shown in Fig. 6–37. Dt6qoth d58id( k,c 1goetermine 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 particle jq9sz,t s(mqri3rj2/ acts in the $+x$ direction. Its magnitude increases linearly from zero at
$x=0$, to 24.0 N at $x=3.0$ m. It remains constant at 24.0 N from $x=3.0$ m and then decreases
linearly to zero at $x=13.0$m. Determine the work done to move the particle from $x=0$ to $x=13.0$ m
graphically by determining the area under the $F_x$ vs. $x$ graph    J

  At room temperature, an oxygen molecule, with md p 26ejdgi.r2 4u/aqeass 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 doubh+zm/d+bl, cpm(0ab e led, by what factor has its speed increased? $ \sqrt{a}$ a =    (b) If its speed is doubled, by what factor does its KE increase?   

  How much work is required to s.rnx9f hc 0.a+z mi:pztop 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-kt0mk x8*k4sy / *s19ptwp ,ezjhfkb+vgcar traveling at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whosea+/,bt*zn c e8 kfks/w string exerts an average force of 110 N on the arrow over a distance of 78 cm. What is the speed o,* fes8 bawn//+ktckzf the arrow as it leaves the bow?    m/s

  A baseball (m=140kg) traveling 32m/s moves x15gi;+c /(yaoasoe f lq(g. wa fielder’s glove backward 25 cm when the ball is caught. What was the average force/ c gg ol a((aqes5xow+.;1iyf exerted by the ball on the glove?    N

If the speed of a car is w3 arqkiznvvg0 - 09/kincreased by 50%, by what factor will its minimum braking distance be increased, assuming ali00r9 zvkgw3n /-k vaql else is the same? Ignore the driver’s reaction time.

  At an accident scene on a leveltl8zc9u7nzh xns+o(c kwp0- fw8*y t2 road, investigators measure a car’s skid mark to be 88 m long. The accident occurred on a rainy day, and the coefficient of kinetic friction was estimated to be 0.42. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakeo7fyt u*8pc n-02t(z+l w8nhw scxzk9 s. (Why does the car’s mass not matter?)    m/s

  A softball having a mass of 0.25 kg is pitched at By the time it reaches the p cgg7 cv18bois j;8x.tlate, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resisb;t 17gxi.s jgc8c8ovtance 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 straig*s r u ftvpl)wiub6855ht up by someone who does 80.0 J of work on it?b5*8)r6uutsp5 fl ivw Neglect air resistance.    m

  A 285-kg load is lifted 22.0 m vertically with r a641z6bi vpcan acceleration by a single cable. Determ4a6icp6vb1 zr ine
(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 consta,h2:ku pddsx) nt, k, of 440N/m How much must this spring be stretched to store 25 J ok p2 :duhd)sx,f potential energy?    m

  A 7.0-kg monkey swings from one branch to another 1.2 m high.zvu8wgl:1v t er. What is the change zw. ul 8vv1t:gin potential energy?    J

  By how much does the gravitational potew7rhvoq,/oa81l q bm 5ntial energy of a 64-kg pole vaulter change if his centervhaloq,mw/b o7qr851 of mass rises about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizontal surface has speed v wgo,hml1vjw*zk 1/fi6po -2j = 65 km/h when it strikes a horizontal coiled spring and is *wv /hm-po1woij f12,j 6k gzlbrought to rest in a distance of 2.2 m. What is the spring stiffness constant of the spring?    N/m

  A 1.60-m tall person lifts a 2e0l(b 7ve(lvy.10-kg book from the ground so it is 2.20 m above the ground. What is the potential energy obve7 (vle(yl0f 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 om4c 2:/ itdmktf a 3300-m peakkt mdi4m :2t/c.
(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 bixr naa 7:8e(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 ianrebax87 (:the spring, where will the end of the spring line up with the ruler marks?    cm

  Jane, looking for Tarzan, is running at top l:r6wcci (i*rvu.xh 9speed (5.3m/s) and grabs a vine hanging vertically from a tall tree in the jung69 ihcrruc*x li.(v:w le. How high can she swing upward?    m
Does the length of the vine affect your answer? ----待选择----yesno 

  A novice skier, starting a*v,kb +a:dd dep19 kcfrom rest, slides down a frictionless 35.0$^{\circ}$ incline whose vertical height is 185 m. How fast is she going when she reaches the bottom?    m/s

  A sled is initially given a shove up a friction+ox2nbthi6/wday lo,/vh hecg/ 1t3 3less 28.0$^{\circ}$ incline. It reaches a maximum vertical height 1.35 m higher than where it started. What was its initial speed?    m/s

  In the high jump, Fran’s kinetic energy is transforvq)xw;jrrji5el 9f37med into gravitational potential energy without the aid of a pole. With what minimum speed must Frawxe)r r3iq5;v9 ljfj7n 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 juvdbd -c ay g/::de*fi(mps vertically upward from the top of a platform with a speed of 5.0 m/s. ev :bd /(ydiagf *-:cd($\alpha)$ 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 consta)yslb( zaa,d f28u6ifnt is 950N/m is attached to a table and is compressed down 0.150 m. (a yf68asla2f,u ( idzb)) 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 Fig.xq-tyh1m d npv .)o8m* 6–39. If the block is to remain on the t1nvtm8 dmoxq -yp.)h*rack, even at the top of the circle (whose radius is r), from what minimum height h must it be released?    r

A block of mass m is attached to the end of a spring (spring stiffness const21irqnrklhgag+ 6+d xf5 aq59 ant k), Fig. 6–40. The block is r6hqi9dngx 2r15 kg5 +lq+f aagiven 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 jumrmyaiysml + mdkeo2,.,z3.i 1a4x + feps from a bridge. She is tied to a bungee cord whose unstretched lenlf x.a 4.,zysm,2mai d+1+ kier om3eygth is 12 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 up to po pnx :uh/l3 3towdc-c(int 1 where it is released from rest. Assuming no fricohul x3tncdp:(3c-/ wtion, calculate the speed at points
2    m/s
3    m/s
4    m/s

  A 0.40-kg ball is thrown with a speed of 12 m/s at95(ofvjx i1 sj 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 tn( u /-tzqp1hvo be placed at the bottom of an elevator shaft. If the elevator cable should brnut p(z/1-hqv eak 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 total mass of the elevator and passengers.

  A cyclist intends to cycle up a nih3;a 5w. vc3ox:ch qyj2np97.8 $^{\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 opposite di1e+ anm4wudo7 eoegd:e5nc/8rections, collide head-on and come to rest. How much t8gnu+7oe 5ec/ad1n :4odwe emhermal energy is produced in this collision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slide 3.55y /a rkmc.+*s8bh cne m high and reaches the bottom with a speed of 2.2m/s How much thermal energy due to friction wa rm*bns/a+ kc c5ehy.8s generated in this process?    J

  A ski starts from rest and snrwnoe7j ab,g01s 1,sk b yw72lides 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 they,qddyfc23lbj/vr9-m- q 7xyai dg 76 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 xw;*jjquxq0 m, and it bounces back to a height of 1.5 m.wx*j xuq;0 (qj
(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 resxo,.7vh kzq;t t, is pulled across a floor with a constant horizontal force of 3x7k to, vzhq.;50 N. For the first 15 m the floor is frictionless, and for the next 15 m the coefficient of friction is 0.30. What is the final speed of the crate?    m/s

  Suppose the roller coaster in Fig. 6–41 pamu 7(j; vzoq/dki6p5dsses point 1 with a speed of If the average force of friction is equal to one-fifth of its weight, wi (oq;i 6m kuv7dpdjz5/th 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 pb))taq t /b2e-ccia+ 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 atta4g de6 y:pnhg +w)wbr)ched to a very light horizontal spring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compressed 5.0 cm and re:)r g6yhepgw)4b+ wndleased, stretches out 2.3 cm beyond the equilibrium position before stopping and turning back. What is the coefficient of kinetic friction between the block and the table?   

  A 280-g wood block is firmly attached to a very l8 : xdlsijq49,p p lt-oho:y.q2+ swdzight horizontal spring, Fig. 6–40. The block can slide 8w oi :xlpdohydl 2s-+: s4pztj 9qq.,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 swing?    m

  Early test flights for the space shuttle used a icrkjw 8 ctxmt;nou1xl-o l39 )*bnn 6d5e73j“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 in the absejxk t33benl96 n8ol u) 5xdjco w;1-ci *7ntmrnce 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 taki6 1)sw5fgjekjt ).tx e a 1750-W motor to lift a 315-kg piano to a sixth-story window 16.0 m above? .tg) ji61tk j)5ws xef   s

  If a car generates 18 hp ;+m:hr 7xo y :0;cpu.rvcj yzbwhen traveling at a steady 88km/h what must be the average force exerted on the car due to frictio:b.:z;j y7vcy +o0c;xp mrhu rn and air resistance?    N

  A 1400-kg sports car accelerates from rest to 95km/h in 7.4 cyub ,..z o(cis. What is the average pbu.z(y,ic c. oower delivered by the engine?$\approx$    hp

  (a) Show that one British nja0ig:e -dn) z5uyo v2:bbm;90y jybhorsepower$ \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.” 1 ywsxhkk 1/6qc2 ,)1tam.pz8wcode j
(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 helw(j7 a qd yt)/dkfu81x l1;t9vv5wa)rktvd;r 1150-kg car slows down from to 65km/h in about 6.0 s on the level when it is in neutral. Approximately whaf7at 5d1 lvk;8lyj9 1wxtaw) ;vk) dtd/ur q(vt power (watts and hp) is needed to keep the car traveling at a constant 75km/h.    hp

  How much work can a 3.0-k (xh-wys 8d1 amma42yhp motor do in 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates a 7.3-kg shos-ch)dzb4ad1sx u*b px 191nyt from rest to 14m/s If this motion takes 1.5 s, what average power c1-py9*asxbdb1)h4 s z1xndu was developed?$\approx$    W

  A pump is to lift 18.0 kg of water per minute thrgkwx5 m41ae 0rw(wss8ough a height of 3.60 m. What output rating (watts) should the pump motorakwmse sg85 1w0 (xw4r have?    W

  During a workout, the foeja4dv66 v4 tp( z:kjlotball players at State U. ran up the stadium stairs in 66 s. The staia4zjt6kdv(l6jve 4p: rs 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 cyclistlw;+upg /uyoeyv cp 3:p*v:k , 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 hp. How steep kfsh /,bejgqe /u ns0xbl)l75x j52x*a hill can it climb at a constant speed of 75km/h if the frictional uenlx,/5l5e xs*bqs xh7 bkgj)j/ 0f2forces add up to 650 N?    $^{\circ} $

  What minimum horsepower must a motor have to be able to drag a 310-kg box av3dwltn / 3a.hlong a level flooln h.d3wav/3tr at a speed of 1.2m/s if the coefficient of friction is 0.45?    hp

  A bicyclist coasts down ffh lbep fmbjufr5(5;r*cl7: :y3hs5 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 designed ti/. fj2nspmtf0s8r c, o compress and reft,pcs .f8mi/2 0n rsjbound 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 -nj/bnqw t y3sqe1*7wqfx 4y0 first 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 mx4w n-qsejtq*/1 03y 7wnqybfuch 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. 6–42) in thqhdb95v poksj/+2 f9ku*v c 9pe 1936 Olympics shows that his center of mass rose 1.1 m from lau hkopv52dvk9u+j/c9p * s9f qbnch 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 i lx*al-,gq4u:itudt 2 n1 8ykln Fig. 6–39 is to remain on the track at all tn8gt u4,1yqk ux lld-lt:2a*iimes, 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 aftej c f9 ze*lwc6 i51,ut,6btcpjr jumping from an aircraft without his parachute opening. He landed in a snowbank, creating a crater 1.1 m deep, but survived with onfzw 6 * 9pclc,ib6eujjct1t,5ly 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 end6 uy4:;d c.euidyji6t is fixed (Fig. 6–4;t:y.dj6diuye u6c4 i 3).
(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 q 14lr:kyn+ co;0ewyo3700-m-high mountain. The climb is made in 5.0 h starting at an elevation q1orcokyly+ ew0: 4n; 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 u0urr4w efd8 *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 / k.kv f .av79m742a qz/ml;s:fe vuv l*syovipeople per hour. If the average lift carries people about 200 m (vertically) higher, es7q/4v. z lvs7;:us9o/kv .2myaviemalvf k f*timate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam at thl/6lh n,qm fc1e rate of 650kg/s and falls vertically 81 m before striking the turbine blad1l6/qfc n mlh,es. 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. qu34w 8qsiwi8 9qj e5rtg2sn/6–44), the difference in your apparent weight at the top of the circular loop and the bottom of the circular loop is 6 g’s — that is, six times your weight. Ignore friction. Show also that as long as your speed is above the minimum needed, this answer doesn’t depend on the size88/4 t3u qwsn95rwgisqqi 2ej of the loop or how fast you go through it.    mg

  (a) If the human body could convert a candok 0zzf,uc59ere 63fly bar directly into work, how high could an 82-k3k,uelrf9 0e5 fc6 zozg man climb a ladder if he were fueled by one bar (=1000kJ)    m
(b) If the man then jumped off the ladder, what will be his speed when he reaches the bottom?    m/s

  A projectile is fired at a96ulvycy. b4oa4ay)c x j 29ajn 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 ii f61 9dfir1uhnside the scale compresses 0.60 mm, and it tells you your weight is 710 N. Now if you jumu1idh6 r f1f9ip 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 grab /qid8w *sr0uys a rope, and swings out over a lake (Fig. 6–45). He releud/ syi*q r80wases 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 dista pv(i-/sx8vjex1 lj, rnce of 5.0 m in 9.0 s. What/ vs8j1 , exxiljr(pv- minimum power output was used to accomplish this feat?    W

  Some electric-power companies use watereqw249e. wc i iga;ed8 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 h8wieq 4g2ie;d ecaw9.our 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;- 7q1 y(ogvx;1ppc5dn*o;i rwp kmmr k is cut in half. What is the spring stiffness constant for k1-mqpo y(;in dcrwg7v * ;opx;mr1p5each of the two resulting springs?   k

  A 6.0-kg block is pushed 8.0 m up a rough 73d7p fl 9y8iloyaez+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 accelera4ux:xzc5re/z9 qt z/1uo-ojrd u4)yy k9 mk1zte from 35km/h to 55km/h in 3.2 s, how long will it take to accelerate from 55km/h to 75km/h Assume the power stays the same, and neglect fuoy54u ydk499o:k mz/q1 e ztxu 1)-crrjz/xzrictional losses.    s

  In a common test for cardiac function (the “stress test”), the patient w2ry0ejafl9m 7qg(:p falks on an inclined treadmill (Fig. 6–46). Estif72m:pr 9 qjygafe0( lmate 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 vertica3;l me-+9 h( 0 yofbjrximagy2lly upward a distance of 500 m, what was its velocity whe20olj;f9i3ramyx +em-b (gh yn 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 /k qya9s(p)homx )1t fa rate of 95kg/s (a) If this water wheel is set up to provide electriq()tm ) 9xahof1sykp /city output, what is its maximum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s