In what ways is the word “work” as used in evs/u1qxzj8ui6pk m 30f (n vj5qeryday language the same as that defined in physics? In what sp1 8u zjqi 3mukn(/5vqjx06fways is it different? Give examples of both.

Can a centripetal force ever do work on an object? Explain)ih5qvbjdc fmt5g r l1h)r 16).

Can the normal force on an oo:c6n4mosd myn :5z0y:b wxv3bject ever do work? Explain.

A woman swimming upstream is not moving with respect to the shore. Is sxnpdi h +;q(e7oy rx:;he doing any work? If she stops swimming and merely floats, is work done n( y: h7e+doxxr;qip;on her?

Is the work done by kinetic friction forces al/geyqsjcl0oa9*19j1 cp1 yu v ways negative? [Hint: Consider what happens to the dishes when you pull a tablecloth out from un99 a ejjpsl q1v*/0yoy11gc cuder them.]

Why is it tiring to push hard against a solid wall even t-ef ptaj35fvfpu46 o6hough you are doing no w 6ff j uatvop-e53f6p4ork?

You have two springs that atek*1builj-a992vg8a 4zy v,wg2i jlre identical except that spring l is stiffer than sprgay2jva8 ijv49w9u1bl* iez,g-kl t2 ing 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 l+z3g lofn; w2 2y5wvqforce on a block that is free to slide on a fo22 +w gvl;z3w fyqn5lrictionless 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 gravitat(ouln* wj wh;)n-g3t xional potential energy change when ynnw-u(hox ;*3l )wjtgou jump as high as you can?

In Fig. 6–31, water balloons are tosse7p1k bba); wzld from the roof of a building, all with the same wzpb 1lbk)7;aspeed but with different launch angles. Which one has the highest speed on impact? Ignore air resistance.

A pendulum is launched from p :sr-rj cv-/j/* wytba point that is a height h above its lowest point in two different ways (Fig. 6–32). During both launches, the prcjrbpjv:/yws/ - -t *endulum is given an initial speed of 3.0m/s On the first launch, the initial velocity of the pendulum is directed upward along the trajectory, and on the second launch it is directed downward along the trajectory. Which launch will cause it to swing the largest angle from the equilibrium position? Explain.

A coil spring of mass m rest)jy3 0. 9vocw ke6pabgcl+h,as upright on a table. If you compress the spring by pressing down with your hand and then release it, cab)ljv,0w9e yc h3oagkcp. +6an the spring leave the table? Explain, using the law of conservation of energy.

A bowling ball is hung from t/ nptz xoy1uq 9 )b,qpr:b3s8qhe ceiling by a steel wire (Fig. 6–33). The instructor pullso8tpbqp q/931x q) nuyzb,:r s 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 without pushing it. Why?

What happens to the gravitational potential energy when i-/habxmzwb :. -; lwowater at the top of a waterfall falls to the pool belowa-omxiz.h;b b :wl-/w?

Describe the energy transformations when a child hops around on a pogo:4w;1jj gf6cc inbc, k stick.

Describe the energy transformations that take place when a skier starttq;::xo*:h o aftm lc-na/j)vs skiing down a hill, but after a time is brought to rest by striking a snowdrif tf;ovo):an cxhm* :q/ -l:jtat.

A child on a sled (total mass m) starts from rest at the top of a hill c:a -;wzef wsmivann -gp:k/5o) fh)3 of height h and slides down. Does the velocity at the bottom depend on the anglmc-vf/wh:k ws5an)f- 3e :; pazogni )e of the hill if (a) it is icy and there is no friction, and (b) there is friction (deep snow)?

Seasoned hikers prefer to step over a fallen log in te+wxt) p-r;u4 3 ttpwxheir path rather than stepping on top and jumping down on the other side u;x r4wp)+-ttxpt 3ew. Explain.

Two identical arrows, one with tphag3 g.l2 gz/sx/ x5swice the speed of the other, are fired into a bale of hay. Assuming the hay exerts a constant frictional force on the arrows, sgga/.xhp /x25z s3gl the faster arrow will penetrate how much farther than the slower arrow? Explain.

Analyze the motion of a simple swinging pendulumeb4qb;qghe )xmo e)g r4 w/5)f in terms of energy, (a) ignoring friction, and (b) taking friction into account. Explain why a graq b )g f4qwh;rbo5)ee4 emxg)/ndfather clock has to be wound up.

When a “superball” idb8muul*3-bx )l57 guemgd fsw+d0h(s dropped, can it rebound to a height greater than its originalg m7sdmuu le- du8fb)b3wd(*0+ xhl5 g height? Explain.

Suppose you lift a suitcase from the floor 3rt e*6q6;ffkg ijqt m )--uhyto a table. The work you do on the suitcase depends on which of the following: (a) whether you lift it straight up or along a more complicated path, (b) the time it takes, (c) the height of the table, and (d3jfh6 gyf qt6;t *uk-)m q-eri) the weight of the suitcase?

Repeat Question 22 for the power needed rather thanf9 : e28w8pa y11ep5icqavyvs the work.

Why is it easier to climb a mountain via a zigzag h*h3 ,p g-pzxctrail than to climb straight upp xcph*-zh, 3g?

Recall from Chapter 4, Example 4–14, that j9w/qxn 3ujv5tgln4pdq6 b7ng/s1+ ayou can use a pulley and 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? Account for this, using energy conxadujvn/3gwn4/snpj q69 +l5q71t gbcepts.

  How much work is done by the gravitational force when a 265-kg pile driver f 69cdz/hqx f5ualls 2.80 m5 dh/z 69cfqux?    J

  A 65.0-kg firefighter climbs a flight of stairs 20.0 m high. How much wor+mjd2ev.8 m 7k:vijzo k is requk 7moiem zdj v+8v2:.jired?    J

  A 1300-N crate rests on the floor. Hkv6lbph4ji xew0)05tow much work is required to move it at constant speed (a) 4.0 m along the floor against a6v b eplj00h)kx54tw i friction force of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (horizontally) pushing a -1f ( f9+j qzlrmzw;hr160-kg crate 10.3 m across a rough floor without acceleration, if the effective coefficient of friction wasq+; f (hr9r-zz lwfmj1 0.50?    J

  A box of mass 5.0 kg is accelerated by a force across a floori;8 df, df7jve at a rate of for 7.0 s. Find the net work ; fv dd,7ef8jidone on the box.   J

  Eight books, each 4.3 cm th:g024am dg*jq5hvf giick with mass 1.7 kg, lie flat on a table. How much work is required to stack them one on top of another? q2g*gm 0dg5vh:fia 4j   J

A lever such as that shown in Firmolbek.t *5:e4s5raca4 oo.-vxs 3pg. 6-35 can be used to liff objects we might not otherwise be able to liffm.tbs*p:4 oerc v53sak5r. -oelo a4x . 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° incli9mf 8a3fz ;usxne and is kept from accelerating by a man who is pushing back on it parallel to the incline (Fig. 6-36). The effecf ;sa m9u83fzxtive 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 a-uu/nkb d,j s2cceleration of 0.10 g up2sb/uu-k d j,nward.    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 is k0 zx+n d4p*ulg9,ncw zhyl.y cs 6/g9linear and that $d_{\mathrm{A}}=10.0$ m and $d_{\mathrm{B}}=35.0$m. Estimate the work
done by force $F$ in moving a 2.80-kg object from $d_\mathrm{A}$ to $d_\mathrm{B}$   J

  The force on an object, acting along the x axis, varies aso:i5 c9gyw hvm3rsj61:n8dx d shown in Fig. 6–37. Determine the work done by this force to move the object (a) from x=0 m to x =683nj9h wr1 gvdd:5 oism :cxy 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 acts in o bcoph 2e ; m62kjq3:llxcr1,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 molece j(,mjhv6/oivk /c t3ule, with mass of $5.31\times10^{-26}$typically has a KE of about$6.12\times10^{-21}$ J .How fast is the molecule moving?    m/s

  (a) If the KE of an arrow is doubled, by what factor has its speed increased? b7 9v/g:-rlyjh n pi9i$ \sqrt{a}$ a =    (b) If its speed is doubled, by what factor does its KE increase?   

  How much work is requ g1hh7;/ogfhq0h nveu-mm ;g+wl-w; vired 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 st i;aae;k08gmwd )y 6paop a 1250-kgcar traveling at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whose string exerts an average force of 11/ tb9a c)ihabx*)i:y t0 N on the arrow over a distance of 78 cm. What is the speed of the arrow as it y )c):a*ai/xti bth9b leaves the bow?    m/s

  A baseball (m=140kg) traveling 32m/s moves a fielder’s glove backward 25 by+9 n+ lxpc+e am6io0/t2l yxcm when the ba2iml96x t/by++ yoxl+paec0 n ll is caught. What was the average force exerted by the ball on the glove?    N

If the speed of a car is increased by 5 /)ona+zzcoe*ef9ka 10%, by what factor will its minimum braking distance be increased, assuming all else is the same? Ignore the driver’s reaction t*zoe/z ck1+a9) efnoaime.

  At an accident scene on a level road, investigator +ga- 8kad3crl pq01iprzc1 z/s measure a car’s skid mark to be 88 m long. The accident occurred on a rainy day, and the coefficient of kinetic friction was estimated to be 0.42. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes. (Why does the car’s m p3ca-k/p ai+dc0qz1 gzr1l8 rass not matter?)    m/s

  A softball having a mass of 0.25 kg is pirtg qa4mr:v;l2 vh3 k/tched at By the time it reaches the plate, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resistance during a pitch, if t:v ktm;gvlh q24r/3arhe distance between the plate and the pitcher is about 15 m.    N

  How high will a 1.85-kg rock go if a7cvt852vza r thrown straight up by someone who does 80.0 J of work on it? Neglect air resivt z2 a7r5v8acstance.    m

  A 285-kg load is liftedvv4jkno m3w0 r/56vzo 22.0 m vertically with an acceleration by a single cab5ovwv ozj6n3vk4 /r 0mle. Determine
(a) the tension in the cable,    N
(b) the net work done on the load,    J
(c) the work done by the cable on the load,    J
(d) the work done by gravity on the load,    J
(e) the final speed of the load assuming it started from rest.    m/s

  A spring has a spring stiffness constanl;bm 7,;m)gq e/dlso po)(utct, k, of 440N/m How much must this sprin sl)mplteo;/)m (;7udb oc gq,g be stretched to store 25 J of potential energy?    m

  A 7.0-kg monkey swings from one branch to another 1.2 m higher. W2ixym+ bj7z,*dy s6k9hal6ennv- i p*hat is the change in pote ya6-s ziyd ,b*vi*927+nlkmnj 6 xphential energy?    J

  By how much does the gravitational potential energy of a 6oast7 7ue8op3j(pcba : 0scw*4-kg pole vaulter change if his center of mass rise 870 cpo(u *bo7 s3estjpacaw:s about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizontal surfibtm mo )y52(zace has speed v = 65 km/h when it strikes a horizontal coiled spring and is brought to rest in a dist)ym m5(btzo2i ance 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 2.20 m abo*ovqicif d*r h) l8/+yve the ground. Wha/qf v8o cl+d)ryi h**it 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 ele.;ps aywp;3u hvation of 1600 m and climbs to the top of a 3300-m peak. a3p;wsyu. p;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 = 53 v+s 8t8pg6oyyN/m hangs vertically next to a ruler. The end of the spring is next to the 15py8 8 ty+ogsv6-cm mark on the ruler. If a 2.5-kg mass is now attached to the end of the spring, where will the end of the spring line up with the ruler marks?    cm

  Jane, looking for Tarzan, is running at top speed (5.3m/s) and grabs a vi 2:4( jfc a++du +aandhoncti*ne hanging vertically from a tall tree in the jungle. How ha( n:cjh+ico+a4+*2fddn u t aigh can she swing upward?    m
Does the length of the vine affect your answer? ----待选择----yesno 

  A novice skier, starting from rest, )i 5a t 9vzy(a1ic*ifstsscqe ,24;yxslides 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 frictoaagi,1w x,- hionless 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 transformed into grae8yl 1 bpyp19 7z5vnwcvitational potential energy without the aid o1p7 z1 yy8clpw5ev 9nbf a pole. With what minimum speed must Fran leave the ground in order to lift her center of mass 2.10 m and cross the bar with a speed of 0.7m/s.    m/s

  A 65-kg trampoline artist jumps vertically upward from the top of a plahoml2cj *v7zbin -z)8 tform with a speed of 5.0 m/s8vhnm-zj o b7*)zl i2c. ($\alpha)$ 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 stiffneupo ,+jdf9i6fn12 eesss 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 0.30-kg ball when rfo1f2j i6epn+sd u 9,eeleased?    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 Fi09bwof0mrg7g g. 6–39. If the block is to remain on the track, even at the top of the circle (fb gwr9mg o070whose radius is r), from what minimum height h must it be released?    r

A block of mass m is attached to the end o( 3ilqwdfw72y 3u5j3v+nat1k vbgck9f a spring (spring stiffness constant k), Ft5w1db(v+u w2lk jgci9yna 7f3k3q3vig. 6–40. The block is given an initial displacement $x_0$ after which it oscillates back and forth. Write a formula for the total mechanical energy (ignore friction and the mass of the spring) in terms of $x_0$ position x, and speed

  A 62-kg bungee jumper jumps fr :si9 o;ji, ;xrku0j3zvhs2 gxom a bridge. She is tied to a bungee cord whose unstretched length is 12 m, and falls a total of 31 m.j g;o2vx:hi;93 suzrisxj,k0 (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 point 1 where it is h81f3sffa;grrf; ; d2ek2zq hwcr p+ 4released from rest. Assuming no friction, calculate t;pqrcrf1wh3z hrs8k2 f4+ff ;ea2g d;he speed at points
2    m/s
3    m/s
4    m/s

  A 0.40-kg ball is thrown with a speed of 12 m/s at a,,sih,fxum04 c f*tyo8 qy ))irk5 kzon 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 plac6 sn2yfdvxix 58u.uk)ed 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 touyi.8 u5n2d 6)kxsxvftal mass of the elevator and passengers.

  A cyclist intends to cycle up a 7.8 k,t3ha4)lf rhiffm;b8z;x + n $^{\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 opposit c, gketd**gmlc-2 6nt eiu;rs69fq5oe directions, collide head-on and come to 9fem ol 5-dg u;k *6qgsecnc2tt6* ,rirest. 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 hignvz ,90uxib7vh and reaches the bottom with a speed of 2.2m/s How mu 9zbuv,x0v7nich thermal energy due to friction was generated in this process?    J

  A ski starts from rest and slides down a 22 *tdvaew .w58l 4s+u/ xyswsq3 $^{\circ} $ incline 75 m long.
(a) If the coefficient of friction is 0.090, what is the ski’s speed at the base of the incline? $\approx$    m/s
(b) If the snow is level at the foot of the incline and has the same coefficient of friction, how far will the ski travel along the level? Use energy methods.$\approx$    m

  A 145-g baseball is dropped from a tree 13.0 m above the ground. sa*bc2/ vieo6
(a) With what speed would it hit the ground if air resistance could be ignored?    m/s
(b) If it actually hits the ground with a speed of 8m/s what is the average force of air resistance exerted on it?    N

  You drop a ball from a height of 2.0 m, and it bounces back to a heige luf;jr- .hmp2 ,tqm2a5yaf3ht of 1.5 m. yfrhl5 3 2j e-uat,m2m.pqfa;
(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 hj7q2 q- nz qpqrx(g/8pulled across a floor with a constant horizontal force of 350 N. For the first 15 m the floor is fricti8q2rqqnjpghq xz-7/ (onless, 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 cxzgkirh2pdra fv5 /i:s0.w 9:4q5ziloaster in Fig. 6–41 passes point 1 with a speed of If the average force of friction is equal to one-fifth of its weight, with what speed will it q9a l :ih i4/.:iwf2r5d vzxgrs05kpzreach point 2? The distance traveled is 45.0 m. $\approx$    m/s

  A skier traveling 12m/s reaches the foot ocjc v y9q pqv7u/w(/s:f 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 attach4yh o 7ovm45sped to a very light horizontal spring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compreso ph5474m vsoysed 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 attached to a very lu-e /on(wraq4f lq) -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 swinguao/-ef- )wnlr(ql 4q?    m

  Early test flights for thepyduu4g2 e4 o: space shuttle used a “glider” (mass of 980 kg including pilot) that was launched horizontally at 500km/h from a height of 3500 m. The glider eventually landed at a speed of 200km/h (a) What would its landing speed have gu2po:u ye44d 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 li5egoztqwvuw 3 .d (:g4ft a 315-kg piano to a sixth-story window 16.t 53qugw4og:e wd v(z.0 m above?    s

  If a car generates 18 hp when traveling at a steady 88km/h whagph z(s qrfg6 ;8/z*lfzu *xi/t must be the average force exerted on *g fz*hl8 /6( qiur/;pszgxfzthe car due to friction and air resistance?    N

  A 1400-kg sports car accelerates from v v2;l6 (k7dsrf5+jj wz7m +d kvp5uonrest to 95km/h in 7.4 s. What is the average power 2jl(d v7 dzn+p5kms; r57j6wk+ vvufodelivered by the engine?$\approx$    hp

  (a) Show that one British v ly2jx)s j4,mhorsepower$ \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 “ki(c8 3qmkbp2j6 k qho k8b77y-zerl eg5lowatt-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 car slow (-3vr 9d7 qtozhh8ogos down from to 65km/h in about 6.0 s on thv -dogq3 8t(rzh 79hooe level 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 in1el.peoij1wdad k:tk 1tm2. 1 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates a 7.3-kg shot from rest to 14m/s If thiv(99k 3qgsp/cwbszg rwm.m,c0 75 mtbs motion takes 1.5 c.z,v cs7g/ (skm 509wmmb9bgqwtrp3s, what average power was developed?$\approx$    W

  A pump is to lift 18.0 khyy).w9,tz cbg of water per minute through a height of 3.60 m. What output rating (watts) should the pump motor have ,.)c9 yyzhwtb?    W

  During a workout, the football playersp.k k5iv v 8h7fly x*e:h.+c,jyftfh- at State U. ran up the stadium stairs in 66 s. The stairs are 140 m long and inclined lyi-f fhp:e.chvv *,7hfx.t5k y +8kjat an angle of 32 $^{\circ} $. If a typical player has a mass of 95 kg, estimate the average power output on the way up. Ignore friction and air resistance.    W

  How fast must a cyclist climb a n,i2gvtyt- 7c9 ujs: a6.0 $^{\circ} $ hill to maintain a power output of 0.25 hp? Neglect work done by friction, and assume the mass of cyclist plus bicycle is 68 kg.   m/s

  A 1200-kg car has a maximum power output of 120 hp. How steep a qwu 0 bt3da-/7)9 bduah7y slbhill can it climb at a constant speed of 75km/h if the fri0ybbw-at7qb ha3l/d9u usd7 ) ctional forces add up to 650 N?    $^{\circ} $

  What minimum horsepower muxmg(cl qk 4m2;st a motor have to be able to drag a 310-kg box along mgl 4(xqmc2;ka level floor at a speed of 1.2m/s if the coefficient of friction is 0.45?    hp

  A bicyclist coasts d+ tt ydr8n3:mwm *nl(u5( ocylown 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 defsqlj8/yyr x 0 x(dq+vere8,o5l2,k6ic4vb rsigned to compress and rebound elastically without any physical damage at speeds below 8km/h If the material of the bumpers permanently deforms after a compression of 1.5 cm, but remains likyfrjlver/ sdxo ec, q+40rbv 62q5(ky 8l 8x,ie an elastic spring up to that point, what must the effective spring stiffness constant of the bumper be, assuming the car has a mass of 1300 kg and is tested by ramming into a solid wall? $a\times10^b$ N/m a =    b =   

  In a certain library the first shelf is 10.0 cm off the g ,e/mnmt45ab ))rgnw c,4 ooiuround, and the remaining four shelves are each spaced 30.0w,)5 ort4m/mo a4,uic)genn b 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 jufm hn(d y/:zzzcm4 ;1q,) cyhimp (Fig. 6–42) in the 1936 Olympics shows that his center of mass rose 1.1 m from launch point to the top of the arc. What minimum speed did he need at launch if he was traveling at 6.5m/df;4c, ):z(y my/cqi1 hnzmhzs at the top of the arc?   m/s

  The block of mass m sliding without friction along the loop,c;q s9r xipy+q4/ moged track shown in Fig. 6–39mi+cq4q; 9yo,rp s/g x is to remain on the 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 parachutm: u; i,sgsxoy d7e4d;e opening. He landed in a snowbank, creating a crater 1.1 m deep, dx , og d:;miss;y7u4ebut survived with only minor injuries. Assuming the pilot’s mass was 78 kg and his terminal velocity was 35m/s estimate
(a) the work done by the snow in bringing him to rest; $\approx$    J
(b) the average force exerted on him by the snow to stop him;$\approx$    N
(c) the work done on him by air resistance as he fell.$\approx$    J

A ball is attached to a horizontal cord of leng8.rl46fxtys z th L whose other end is fixed (Fig. 6–43).4.yls z86xr ft
(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 tyyxzdll2a:mc xki+bud7y88 n014k w-o the top of a 3700-m-high mountain. The climb is made in 5.0 h starting at an elevation of 2300 m. Calculate 0 8ylc:wzlxdbkm7uk+ 4i xyy2-n1da8
(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 breo3zm vh( gw6:zaks when 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 m2ukze 3ei-yp ef68a 7gove 47,000 people per hour. If the average lift carries people about 200 m (vertically) higher, estimate the power nei7z328eepy e6-gaf kueded.$a\times10^b$ W a =    b =   

  Water flows over a dam at the rara xh+4k-w7v 8)yinav:n2lgk te of 650kg/s and falls vertically 81 m before sway478knh:i- )l2rn xvvga k+triking the turbine blades. Calculate
(a) the speed of the water just before striking the turbine blades (neglect air resistance), $\approx$    m/s
(b) the rate at which mechanical energy is transferred to the turbine blades, assuming 58% efficiency.    W

  Show that on a roller coaster with a circular vertical loop (Figpf4 ke-dv hw5kc.d 0,y. 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 you fdw 4hp.kec,-kv5d 0yr weight. Ignore friction. Show also that as long as your speed is above the minimum needed, this answer doesn’t depend on the size of the loop or how fast you go through it.    mg

  (a) If the human body couldd l-/qgo5*g v 9uzo yno*qog8: convert a candy bar directly into work, how high could an 82-kg man climb a ladder if he o*gg8oyovqq*gzd/95 :-o u lnwere 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 fire mcebao:r3 fhz:vuq 7kn53-x9d at 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 sx-u(yin*f ;ascale compresses 0.60 mm, 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? a ix; -ufsy(*n   N

  A 65-kg student runs at 5m/s grabs a rope, and swingss wpb6u 3a(u9qe./ onv out over a lake (Fig. 6–45). He releases the ropbw (qu v 6/3aeson.pu9e 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 aeh6 fds0:v /t8(wj pqgthlete climbs a vertical distance of 5.0 m in 9.0 s. What minimum power output was used to accomplish this feat? 0 6 fpj 8sw/v(qhegd:t   W

  Some electric-power companies use water to store energy. Water is pumped by rd,su 1c dii9l/eversible turbine pumps from a low to a high reservoir. To store the energy produced in 1.0 hour by as uddic91 ,i/l 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 half0bw llbj-qpg3w* 5( ai. What is the spring stiffnes*0 lb-agi35w lq(j wbps constant for each of the two resulting springs?   k

  A 6.0-kg block is pushed 8.0 l z vm876ih*qcm 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 tocy6y.35 gzei ey+n xj::i0 vnyc/zz) f 55km/h in 3.2 s, how long will it tn /ezg3f+yzx )i5i0cv.j6z: :y c yneyake to accelerate from 55km/h to 75km/h Assume the power stays the same, and neglect frictional losses.    s

  In a common test for cardiac function (the “stress test”), the patient walks oqmx: +i0 nwv 10fjxtk m+mp*7gn ankmjx+ nitgqf*p0x1:v0m+w m 7 inclined treadmill (Fig. 6–46). Estimate the power required from a 75-kg patient when the treadmill is sloping at an angle of 15 $^{\circ} $ and the velocity is 3.3km/h (How does this power compare to the power rating of a light bulb?)$\approx$    W

  (a) If a volcano spews a 500-kg rock vertically upwardxf efn)t6g;*kohc71i a distance of 500 m, what was its ve; fc6*nhgof k71xti)elocity 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 water wheel from a height of 2.0 m at a rate of 9v7-e:tgn a n+j5kg/s (a) If this water wheel is set up to provide electricity output, what is its maximum powe7 agvnt -jen:+r output?    W
(b) What is the speed of the water as it hits the wheel?    m/s