In what ways is the word “work” as used in everyday language the.3ry ne:mpowh(i k/v/ same as that defined in physics? In what ways is it different? Give examples of m.(kn /3v:opiweyr/hboth.

Can a centripetal force everkpc wkuw5+5o8 r1f -z m*pr)rkljuhfx u:+-u 2 do work on an object? Explain.

Can the normal force on an object ever do work? Eura3o/n k3:qbr+8 3zdlb8d*o wqs( cf xplain.

A woman swimming upstream is not moving with respect to the shore. Is svf2a ) daa(qv*he doing any work? If she stops swimming and merf(2v *aaav q)dely floats, is work done on her?

Is the work done by kinetic frictionj)d 2s30 stwfmk8cxj 0 forces always negative? [Hint: Consider what happens to thfkssjd)0c2 0 3mwxj 8te dishes when you pull a tablecloth out from under them.]

Why is it tiring to pus jbs -rz7w h9wxi7o:m)h hard against a solid wall even though you are doing no workiw 7z b-)rxw9:oms j7h?

You have two springs that a0 z(a j lcvnxr74yjfpk r)n)73re identical except that spring l is stiffer than springjn)3vn ck 4)(rl77yafxz0jrp 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 2ouon 8b0 9gnq ic*f,ja block that is free to slide on a frictionless surface (Fig.6-30). The block starts from rnb 2c,ngj8ui*q0o f9oest 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 gravitational potential energy change w :5fa7i1z amjhioiy 02hen you juho21mzf 5y jaii:0 ai7mp as high as you can?

In Fig. 6–31, water balloons a+08jmn deha cr,. /2 ijr )bcxzwu)iv5re tossed from the roof of a building, all with the /crne. r i+v c)iu58wj,h0dbza2j x)m same speed but with different launch angles. Which one has the highest speed on impact? Ignore air resistance.

A pendulum is launched from w1dnk xjj ;-:/g9ftpd 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 thjj/:dp9 w; kxd-tnfg1 e trajectory. Which launch will cause it to swing the largest angle from the equilibrium position? Explain.

A coil spring of mass m rests upright on a e0yfax wn/49g table. If you compress the spring by pressing down with your hand and then release it, can the spring leave the table? Exp049x/ay f wneglain, using the law of conservation of energy.

A bowling ball is hung from the ceiling )oxbl+2t fy; kby a steel wire (Fig. 6–33). The instructor pulls the ball back and stands against the wall with the ball against his nose. To avoid injury the instructor is supposed to rt ) ;xk+ylbof2elease the ball without pushing it. Why?

What happens to the gravitationrqu175wm f o1f(ye .tkal potential energy when water at the top of a waterfall falls tumw qyo k1.r7(5f tef1o the pool below?

Describe the energy transformations when a child hops around on a pogo stick.3lc28x6+4dh: )xw1xkgnu4dk w nntv,j.d twi

Describe the energy transforma o-pb gyb1i+yr c8c6qsf1v52rtions that take place when a skier starts skiing down a hill, but after a time is brought to rest by striking a5cborpi yfb+qv 6 -21srcyg18 snowdrift.

A child on a sled (total mass m) star1+-h ikj* 9d w -sm(qgl)mlj3uvwx;mcts 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 is no friction, and (b) -1*hjk+wvg)xu- m cmd3 qlwjlmi;( 9sthere is friction (deep snow)?

Seasoned hikers prefer to step over a fallen log i6h(:y*z.vu(ybvlug mth :8 df n their path rather than stepping on top and jumping down on the othz.yuh tu dy :glmbvh*v6f(8: (er side. Explain.

Two identical arrows, one with twice the speed of the otherp:p gdw h14+ts, are fired into a bale of hay. Assuming the hay exerts a constant frictional force on the arrows, the faster arrow will penetrate how much farther than the slower gp1+p: s4hwdtarrow? Explain.

Analyze the motion of a simple swinging pendulum in terms8akz6of: l/b t of energy, (a) ignoring friction, and (b) taolk8/fb6 : ztaking friction into account. Explain why a grandfather clock has to be wound up.

When a “superball” is dropped, can it rebound to 5ppmo *a2jc ne8c,z(za height greater than its origicc *jez(2o mn p,az58pnal height? Explain.

Suppose you lift a suitcase from the floor to a kvouc0u :;a bzfxvo;+s ); 2,ov.hqmftable. 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 (d) the weig.hu:v )f bv;;0xoufkaoz vo2m sq,c+;ht of the suitcase?

Repeat Question 22 for the power needed rather thany1udzd e -mc9-g/ q2tl the work.

Why is it easier to climb a mountiw0 6 ijajxk* 5ag)+slain via a zigzag trail than to climb straight u)sij0j+ wagk5x *a il6p?

Recall from Chapter 4, Example 4–14, that you can use a pulley and ropes tooi/(fr0x.t9 s5 tttpg decrease the force needed to raise a heavy load (see Fig. 6–34). But for every meter the loa9s/g.t(5itt 0tpf o xrd is raised, how much rope must be pulled up? Account for this, using energy concepts.

  How much work is don3m -/fgwlijm,qt ,4 r sls69ewe by the gravitational force when a 265-kg pile driver falls 2ms qi6rw,/gmf wtl43 e,-s9lj.80 m?    J

  A 65.0-kg firefighter rv *f +azxt 3ed7g+*h:v*sfxzclimbs a flight of stairs 20.0 m high. How much work is requiv3*fdxz a*f +xs:* gvz+7ehr tred?    J

  A 1300-N crate rests on the floor. H41rkf g 6*a68jcufm:gk*u jncow much work is required to move it at constant speed (a) 4.0 mg:a r gk u4ff66j1j*cnk*umc8 along the floor against a friction force of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (hihc d0:s7(g b5p,spzn orizontally) pushing a 160-kg crate 10.3 m across a rough floor without acceleration, if the effectzb0 ip7sd (p5cgh,s:n ive coefficient of friction was 0.50?    J

  A box of mass 5.0 kg is accele0 c t9,+ce+ z+ets -kz3kkl(x xgsb,ixjvr3 u;rated by a force across a floor at a rate of for 7.0 s. Find the net work donv + sek;k(zecgt+,ju0 93tli3crx xk+z s-b,xe on the box.   J

  Eight books, each 4.3 cm thick with mass 1.7 kg,7lvxq pp 8d) dvkfmj0+3l43 qaivy2x4 lie flat on a table. How much wqf) 2 3a340lvmlj pv 4py kqxd87x+vdiork is required to stack them one on top of another?    J

A lever such as that shown in Fig. 6-35 can be used to liff object;l .iw:f:wa rq v4qq :ixzc(1fs we might not otherwise be abq:1 w.f 4xcw ivi;ar:fq(qz:lle 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 fr*f :h)vrpq+y qom accelerating by a man who is r vhpqy) *+q:fpushing back on it parallel to the incline (Fig. 6-36). The effective coefficient of kinetic friction is 0.40. Calculate:
(a) the force exerted by the man,    N
$(b)$ the work done by the man on the piano,    J
$(c)$ the work done by the friction force,   J
$(d)$ the work done by the force of gravity,   J
$(e)$ the net work done on the piano   J

  (a) Find the force required to give a helicopter of mass M an accelerationpwxef4 uhha)t7, w1d+bw 485oy5*m6 h icjkcd of 0.10 g upmw*hdpx hew7c 54kyc,8+6dt u51aw 4bo )ij hfward.    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 thenl g 5uft6neei0:0:pq 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, varies asarc) 9wm:gt2k+vl f3 n shown in Fig. 6–37. Determine the work done by this force to move the object (a) frgr )twk9ncm f2lav3:+om 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 acts in the ajom 4wezh;wx6t/76hz y lv- sk4e:6q$+x$ 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,d1w4wjv:ski1 bn f r8, an oxygen molecule, with mass of $5.31\times10^{-26}$typically has a KE of about$6.12\times10^{-21}$ J .How fast is the molecule moving?    m/s

  (a) If the KE of an arrow is doubled, by what factor has its yz4m3 8snd+suspeed increased? $ \sqrt{a}$ a =    (b) If its speed is doubled, by what factor does its KE increase?   

  How much work is required to stop a+kq: (d nellbf m9m-jbtmz,**2kj (w br /*zssn 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-kg, lyyaa9l*ylja3b*1/uvfj b4 car traveling at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whose strin:rrsh j m+.pe(g0b r.rg exerts an average force of 110 N on the arrow r bsj.(r0re.ph+ mg:r over a distance of 78 cm. What is the speed of the arrow as it leaves the bow?    m/s

  A baseball (m=140kg) traveling 32m/s moves a fielder’s glove backward 25 agd(u6 ;-zowp cm when the ball is caught. What6 wuzp og(ad;- was the average force exerted by the ball on the glove?    N

If the speed of a car is increased by 50lp3l,dv3g 2fzda-i p)%, by what factor will its minimum braking distance be increased, assuming all else is the same? Ignore the drivep,-f p ld2d3)3 lavgzir’s reaction time.

  At an accident scenechp*vf0d;0 y-c* fqkr on a level road, investigators measure a car’s skid mark to be 8;*p0dq yvfh-c0ckrf *8 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 mass not matter?)    m/s

  A softball having a mass of 0.25 kg is pitched at idj90 0nvu0ig/wjcu 6 By the time it reaches the pl0u0 icu6v9/n0d jg iwjate, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resistance during a pitch, if the distance between the plate and the pitcher is about 15 m.    N

  How high will a 1.85-kg rock go if thrown straight up by someone who does 80.0 Jeg1n)iw e4g+r of work 1ew 4+ggr)ne ion it? Neglect air resistance.    m

  A 285-kg load is lifted 22.0 m vertically with an accelerwjl5 lptbb4d d)e802i ation by a single cable. Determine lb i)de2 b80dt4 p5jwl
(a) the tension in the cable,    N
(b) the net work done on the load,    J
(c) the work done by the cable on the load,    J
(d) the work done by gravity on the load,    J
(e) the final speed of the load assuming it started from rest.    m/s

  A spring has a spring stiffness constant, k, of 440N/m How mu47 flztu 7(5y,yodisn ch must this spring be stretched to stld f75ioy,s uz 4nt(7yore 25 J of potential energy?    m

  A 7.0-kg monkey swings from one bran* ia m9edpmg n8i; -rlr5xjr9- 2dru3ych to another 1.2 m higher. What is the change in poter95rrlmiy8a2 mr3-xd i* ng ;pduje-9ntial energy?    J

  By how much does the gravitational potential energy of a 6dcj*t) ze64m7*jeype 4-kg pole vaulter change if his center of mass risesj*mezd7 e6)cj ep*4yt about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizontal sur 0(bgs/yxc 8psface has speed v = 65 km/h when it strikes a horizontal coiled spring and is brought to rest in a px0/g 8sy(scb distance of 2.2 m. What is the spring stiffness constant of the spring?    N/m

  A 1.60-m tall personx)h92 pu8okgal - o 7+e1hsovn lifts a 2.10-kg book from the ground so it is 2.20 m above the gokv 2ph -eolax9o1+78)husnground. What is the potential energy of the book relative to
(a) the ground,    J
(b) the top of the person’s head?    J
(c) How is the work done by the person related to the answers in parts (a) and (b)?    J

  A 55-kg hiker starts at an elevation of 1600 m and cl)y;pmha/ykf: +gg 8p nimbs to the top of a 3300-m p g m/;:)h8f yykg+pnpaeak.
(a) What is the hiker’s change in potential energy?    J
(b) What is the minimum work required of the hiker?    J
(c) Can the actual work done be more than this? Explain why. ----待选择----yesno 

  A spring with k = 53N/m hangs vertically next ton90(tana wv q6 a ruler. The end of the spring is next to the 15-cm mark on q( 6nwtn9a av0the 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 tot1n gzuxxxu 5u(-kc5)7rek8pp speed (5.3m/s) and grabs a vine hanging vertically from a tall tree in the jungle. How high can she swing upward 5x)t( kpxrg751kn ecu8- uuxz?    m
Does the length of the vine affect your answer? ----待选择----yesno 

  A novice skier, starting from rest, slides dowm qlbbgz;3j4; zldh4o0: 8up dn 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 gi24gcet1laro7e8g +us ven a shove 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 is trans*ebze,kq4 kd.jah6z- : g7 ajyformed into gravitational potential energy without the aid of a pole. With what minimum speed must Fran leave the ground in order to lift her cekj6,gyeqz7j * z4h.b d:kaae-nter 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 thsh +gbh1;o1 xxt-,hhx e top of a platform with a speed of-h s,gxhx1h+; xobth1 5.0 m/s. ($\alpha)$ How fast is he going as he lands on the trampoline, 3.0 m below (Fig. 6-38)?$v_2$ $\approx$    m/s
(b) If the trampoline behaves like a spring with spring stiffness constant 6.2×10$^{4}$ N/m , how far does he depress it? $y_3$ =    m

  $\text{A projectile is fired at an upward angle of 45.0o from the top of a 265-m cliff with a speed of 185m/s. What will}\\\text{be its speed when it strikes the ground below?(Use conservation of energy.)}$    m/s

  A vertical spring (ignore its mass), whose spring stiffness constant is 950N/m w3 kud)i-rwa3is attached to a table and is compressed down 0.150 m. (a) What upward speed can it give to w wu)kar33i-d 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 slid9a(aq d zidb92es without friction along the looped track shown in Fig. 6–39. If the block is to remain on theda(9d2zba 9q i 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 spring (spr. /k)q dnpxlwdoz .6k1ing stiffness constant k), Fig. 6–40. The block is given an i qokxl/.zk. 6pn)d 1dwnitial 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 f +k)yg mt*l;ofd wp :pg0 5cw6f(+qchdrom a bridge. She is tied to a bungee cord whose unstretched length 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 applie cf5:pdf+c *kh ty06wm;gop l +dw)(qgs. $\approx$    N/m
(b) Calculate the maximum acceleration she experiences. $\approx$   m/$s^2$

  The roller-coaster car w )1 wccyy8e57x 5ezfzshown in Fig. 6–41 is dragged up to point 1 where it is relec1w5yzxe)8ey5 w7fz c ased from rest. Assuming no friction, 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 at an angle of8+q.klq+yc w2 mi-tu n 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+xpg av14iy2e placed at the bottom of an elevator shaft. If the elevator cable should break when the elevator is at a height h above the top of the spring, calcul vpia+xy4 2ge1ate 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 cycas6w.k 1(z ( /-uonqy+b rih21hblfo tle up a 7.8 $^{\circ} $ hill whose vertical height is 150 m. Assuming the mass of bicycle plus cyclist is 75 kg,
(a) calculate how much work must be done against gravity.    J
(b) If each complete revolution of the pedals moves the bike 5.1 m along its path, calculate the average force that must be exerted on the pedals tangent to their circular path. Neglect work done by friction and other losses. The pedals turn in a circle of diameter 36 cm.    N

  Two railroad cars, each of mas:x;xmu0 tno+hs 7650 kg and traveling 95km/h in opposite directions, collide head-on and come to rest. How much thermal energy is produced in this 0:m oxu h;n+txcollision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slide 3.5 mslwuq,a a s3v 6l6jm33 high and reaches the bottom with a speed of 2.2m/s How much thermal energy due to friction was generam63wjsa3l6 lq ,vasu 3ted in this process?    J

  A ski starts from rest avfdwq p+k3rmo)8 bz(cj0 t8e( nd slides 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 abovfl:/mxgs2wz sl-sf l(g zh7, ;e the ground.
(a) With what speed would it hit the ground if air resistance could be ignored?    m/s
(b) If it actually hits the ground with a speed of 8m/s what is the average force of air resistance exerted on it?    N

  You drop a ball from a height of 2.0 m, and it bounces back t73 jkg vjii tetr7ql863 6u,sho a height of 1.5 mh, qr7igkule v8jt63 j76si3t .
(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 a 8u7anru- / ffn82tfmdconstant horizontal force of 350 N. For the first 15 m the floor is frictionless, and for the next 15 m the coefficient 2/adn788ufnfr -muf t 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 n.w ;-q6dlmvz a speed 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 traveled q.mz;6lndw-v is 45.0 m. $\approx$    m/s

  A skier traveling 12m/s reaches the foot of a steady upwardy rwr .q n0bp,u9qij1/ 18.0 $^{\circ} $ incline and glides 12.2 m up along this slope before coming to rest. What was the average coefficient of friction?   

  A 0.620-kg wood block is firmly attached to a very light horiz+ i6) )iltolzsontal spring (k=180Ntzl)o s+ i)l6i/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compressed 5.0 cm and released, stretches out 2.3 cm beyond the equilibrium position before stopping and turning back. What is the coefficient of kinetic friction between the block and the table?   

  A 280-g wood block is firmd oo(+q8d)5ub vy+ ay dzj/ec)ly attached to a very light horizontal spring, Fig. 6–40. The block can slide along a table where the coefficient of d8(yq)o juzyvb) /ec5+dd+oafriction 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 “glider” (mass of 980 kg incl-o+yf5dlnix - jx)yz* uding pilot) that was launched horizontally at 500km/h from a height of 3500 m. The glider eventually landed at a speed of 200kdjyi o-*+nzy)x-lf x5m/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 ec 2543kacqwx9s lx; mpiano to a sixth-story windocsx m2a c4k 5lx;e93wqw 16.0 m above?    s

  If a car generates 18 hi +,zei0 rwh+lp when traveling at a steady 88km/h what must be the average force exerted on the car due to friction and air resistance++i0zl he irw,?    N

  A 1400-kg sports car accelerates from rest to 95km/h in 7.4 s. What is t v0wzw ge,7f2p-ezii 4he average power delivered by the eng7 ,v02f-zw4wpgi eiezine?$\approx$    hp

  (a) Show that one British(ta q.j8)yac c; ymvxt)r(jf :l xk,e+ horsepower$ \mathrm{ft}\cdot\mathrm{lb/s}$ is equal to 746 W.
(b) What is the horsepower rating of a 75-W light bulb?    hp

  Electric energy units are often expressed in the form xyz 86xpjljc,v; j/ur2r 1p9,xdh )clof “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 car slows down from to 65km/h in about 6.0 s :/a wzyvj+szhe5wy4. on the level when it is in neutral. Approximately what power (watts and hp) is needed +zawejz y54sy:hv . w/to keep the car traveling at a constant 75km/h.    hp

  How much work can a 3.0-hp motor do i/ykxm.gwio,n;j97z)v jl q 1cn 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter acceleratxoe* e- w9f+fles a 7.3-kg shot from rest to 14m/s If this motion takes 1.5 s, what average power was de*eeffxo wl -+9veloped?$\approx$    W

  A pump is to lift 18.0 kg of water per minute through a h1 .v8px5hi-; rtba a 4-de6l8qzsffzjeight of 3.60 m. What output rating (waxp 1ab8lszt8 -r-j .eh 5a46vqizd;fftts) should the pump motor have?    W

  During a workout, the football players;2r,1 hdi lj1 b0aoa7z :lzkir at State U. ran up the stadium stairs in 66 s. The stair1ho r zl,ail;d07abk ir j12:zs 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 cyclist clq .jvs. wa7tifi2p2i .8)t q* (yhomigimb 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 / .ikwaytbv32 output of 120 hp. How steep a hill can it climb at a constant speed of 75km/h if the frictional 3./ i2byvwk taforces add up to 650 N?    $^{\circ} $

  What minimum horsepower must a motor have to be able to drag a 31mwn4y, j.uzfdd: x6p1osh4h ;0-kg box along a level floor at a speed of 1.2m/s if the coefficient of .,fj wnysuz4x;1pod:d4 6mhhfriction is 0.45?    hp

  A bicyclist coasts down a 7.0 wa h5szb3 w u9b ma hmo(lenm28z:3w/)$^{\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 hegqa 8,6 /6c9,xahy g) ylvbpaave built “5mi/h(8km/h) bumpers” that are designed 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 like an elastic spring up to that point, what must the effective spring stiffness constant of the bumper be, assuming the car h6 ,vq)y ,lg9hab x8ec/ ya6gapas 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 ground, and the/ f (+ 1dxxwv-poubk5z 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 avexkf-x(bv /pzd5o1uw + rage shelf holds 25 books, how much work is required to fill all the shelves, assuming the books are all laying flat on the floor to start? $\approx$    J

  A film of Jesse Owens’s famous long jump (Fig. 6–42) in the 1936 Olympics sj m5bj 5an8u/bq6n,d xhows that his centerjbmu,nb85danj5 q x 6/ of mass rose 1.1 m from launch point to the top of the arc. What minimum speed did he need at launch if he was traveling at 6.5m/s at the top of the arc?   m/s

  The block of mass m sliding without frict79c7(ksac km bp8:mxdngda8 8ion along the looped track shown in Fig. 6–39 is to remain on the track at all times, even at the ds 9(n 8dakc7:ba8xcmmg7 pk8very 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 o .vrbu ;93 k5ltl+vobz2z4r;rdk :t aan aircraft without his parachute opening. He landed in a snowbank, creating a crater 1.1 v95zz+uo4.;oltrvrb 3;dr2: a bt klk m deep, but survived with only minor injuries. Assuming the pilot’s mass was 78 kg and his terminal velocity was 35m/s estimate
(a) the work done by the snow in bringing him to rest; $\approx$    J
(b) the average force exerted on him by the snow to stop him;$\approx$    N
(c) the work done on him by air resistance as he fell.$\approx$    J

A ball is attached to a hoh/vgmb :bl ix.8s6ih3rizontal cord of length L whose other end is fixed (Fig. 6–43). 3 im68 il.b gshvx/bh:
(a) If the ball is released, what will be its speed at the lowest point of its path?
(b) A peg is located a distance h directly below the point of attachment of the cord. If h=0.8L what will be the speed of the ball when it reaches the top of its circular path about the peg?

  A 65-kg hiker climbs to the top of a 3700-m-high mountain. The climb is madek rfb yli h,(v4v.xi-2zq :;ve in 5.0 h starting atylvhx .-z,i f;v:rbq(i ev2k4 an 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 wfertr 97d;pd +l.5nos hen 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 claim,w48bmvc 0s -ncv -zurs that its lifts can move 47,000 people per hour. If the average lift carries people about 200 m (vertrv4n8 bvmuz- wcsc0 -,ically) higher, estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam at the g76mj+mn ph9frate of 650kg/s and falls vertically 81 m before strikinghp 6+7gm9mnjf 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 (Fig. 6–44), the dif keh3iv8lc),kj,i ss1ference 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 siivski,sk31ecl ,)h 8 jze of the loop or how fast you go through it.    mg

  (a) If the human body could convert a candy bar 4 3gmc;wi lydt z/gtq.x.qm+ -directly into work, how high could an 82-kg man climb a ladder if he were fueled by on.g.twltm4my3qz+ g;dc q /-xie 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 upward angle *sa4 ,lhh jgg2of 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,(ak xaa)lugfzi 5ze5z aq:93, the spring inside the scale 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 readg5aqf zl ,5i):z9xakua(ez 3 a at its peak?    N

  A 65-kg student runsl n,ng6yg0n:k jhx(k 4 at 5m/s grabs a rope, and swings out over a lake (Fig. 6–45). He releases the rope when his velo0hn4nxl gy6(ngjk,k: city is zero.
(a) What is the angle when he releases the rope?    $^{\circ} $
(b) What is the tension in the rope just before he releases it?    N
(c) What is the maximum tension in the rope?    N

  In the rope climb, a 72-kg athlete climbs a vertical distance oxurx3e08j 2j8 u7uo 8fyfwd+ ff 5.0 m in 9.0 s. What minimum power output was used to8d0+eujx 2fwuou38jf 8fy7xr accomplish this feat?    W

  Some electric-power companie hwnz)r(wj- h+s use water to store energy. Water is pumped by reversible turbinehj z)h rn-+w(w pumps from a low to a high 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 constanpu/.*xbd ld0e z:c, vmt k is cut in half. What is the spring stiffness ce0dudx: bzl,vm */pc .onstant for each of the two resulting springs?   k

  A 6.0-kg block is pushed 8.0 m u8(:ps cwa4eb/ (lxvi xc(jpy0p 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 to 55km/h in 3.2 s, ve6;b)1gzxhcq )*c u show long will it take to accelerate from 55km/h to 75km/h Assume the power stays the same, and ne);ube gcvcz6x1s)h *q glect frictional losses.    s

  In a common test for cardiac functionr u4zq acs59e) (the “stress test”), the patient walks on an inclined treadmill (Fig. 6–46). E)4 urca5 eq9szstimate 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 v+es58h e 9 pr7pjrb3df0. qtocertically upward a distance of 500 m, what was its velocity w+ 7shrr90cqo 8eppd.t3 e 5jbfhen 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 w5lw cpt,m6;b rheel 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 maxir b;6p,lmt cw5mum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s