In what ways is the word “work” as used in everyday language the sln /k8rfn,rl4 ame as that defined in physics? In what ways isr8,r4l fn/n kl it different? Give examples of both.

Can a centripetal force ever do work on an ob85kc(udn .0pxol l9p xject? Explain.

Can the normal force on my+;f * ufh/dodq ufjui-*37eyt oj1,an object ever do work? Explain.

A woman swimming upstream is not moving with respect to the shore. Is she doing gdd2:ar4wz,nany wog,n 42a:rddzwrk? If she stops swimming and merely floats, is work done on her?

Is the work done by kinetic friction forces always ne6l,qdh-lmz. h c nn1/wgative? [Hint: Consider what happens to the dishes h d/-,.1hqzn6 mlnclw when you pull a tablecloth out from under them.]

Why is it tiring to ukxn..8z ym+sj lo+cuv6 + yd8y*h 9fjpush hard against a solid wall even though you are doing no wok*dvoc lx+ fyn8.u .jjy8h+6u9zs my+rk?

You have two springs tha0cmpfcueuvkdsg 68r)5nn* 8-t are identical except that spring l is stiffer than sprind6u)u s n 0cfcn8vmpgr8e-5 *kg 2 $(k_1>k_2).$ On which spring
is more work done $(a)$ if they are stretched using the same force, $(b)$ if they are stretched the same distance?

A hand exerts a constant horizontal force on a block that izc2* i-c3 :fgdk hk(vzs free to slide on a frictionless surface (Fig.6-30). The block starts from rest at þoint A, and by the time it zhd23vfg-ikc: (*z kc 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 muchx 7-dwhy3qq*r7 t *u ac)i.bkp does your gravitational potential energy change when you jump as high as you can?u *c-7hx*q7tad brpk3 .yqi)w

In Fig. 6–31, water balloons are tossed from the roof of a6 0vmosojb; 0z 9uwdj5 building, all with the same speed but with different launch angles. Which one has the highes6so w09oubjmz0 jdv; 5t speed on impact? Ignore air resistance.

A pendulum is launched from a point tha(5ai 2y3 bn 4noxw-jxqt 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 p4i( nx5-jy bwoaqn3x2 endulum is directed upward along the trajectory, and on the second launch it is directed downward along the trajectory. Which launch will cause it to swing the largest angle from the equilibrium position? Explain.

A coil spring of mass m rests upright on a table. If you compress t0rst q4rd *ab1he spring by pressing down with your hand and then release0s4*tbd 1rr aq 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. 6–33). Tek v39j4xes m)zzd8):7cjxn ahe instructor pulls the ball back and stands against the wall with the ball against his nose. To avoid injury the instructor is supposed to release the )jxzee 34m) c9nxkzsdaj87: v ball without pushing it. Why?

What happens to the gravitational potential ene -v *pfgc bn:q70l,kjkrgy when water at the top of a waterfall falls tnfl-cqpk:v 7*b,j kg0o the pool below?

Describe the energy transformations when a childm fha22 js99hg hops around on a pogo stick.

Describe the energy transformations that take place when a skier starts skitbdc4 xc-z1 y/s2wp7s ing down axw y t-d1cs2pbs/z7c4 hill, but after a time is brought to rest by striking a snowdrift.

A child on a sled (total mass m) starts from rest at the top oa:c t -+h5cypmgqsi 33f a hill of height h and slides down.-t:i3 +ymca5sgcqh p3 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) there is friction (deep snow)?

Seasoned hikers prefer to step ie7y)3 cp 0pbvover a fallen log in their path rather than stepping on top and jumping d0)pbyvp c37ie own on the other side. Explain.

Two identical arrows, one with twice the speed ofa-.t kfg9 n9 (sfacnk, the other, are fired into a bale of hay. Assuming the hay exerts a constant frictional force on the arrows, the faster arrow will penetrate how9,aag(-kf9cs.tk nn f much farther than the slower arrow? Explain.

Analyze the motion of a simp4z8 8-ereffj,f1vh-kuz w)iz le swinging pendulum in terms of energy, (a) ignoring friction, and (b) takingj8zf zfu,kh1-ev rei)wz4f8- friction into account. Explain why a grandfather clock has to be wound up.

When a “superball” is dropped, can it rebound to a heigh if4u*k/p f.1ky4 dgcrt greater than its original hei1 rk*f4 fi4/.ckug ypdght? Explain.

Suppose you lift a suib 6yv;c 0wl8 rbu7qw-itcase from the floor to a table. The work you do on the suitcase depends on which of the following: (a) whether you lift it straight up8;y blbcvu6wi q0-rw7 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 r+j0n0bqd wshhmv aa;dk4( ;2 the power needed rather than the work.

Why is it easier to climb a mountain via fopvrge48j 7) a zigzag trail than to climb straight up7regp8fov )j4 ?

Recall from Chapter 4, p xzkchn*5+8wExample 4–14, that you can use a pulley and ropes to decrease the force needed to raise a heavy loadkx5 zp *8n+hcw (see Fig. 6–34). But for every meter the load is raised, how much rope must be pulled up? Account for this, using energy concepts.

  How much work is done by the gravitational force when a 265-kg pile driver falhh4yx.j y*r5lls 4yyrhj*.lh x5 2.80 m?    J

  A 65.0-kg firefighter climbs a flight of stairs 20.0 m high. How much work i./kdn0gun uc3s required? nc/k.g3 0un du   J

  A 1300-N crate rests on the floor. How m veitu;uufrf 66 037atuch work is required to move it at constant speed (a) 4.0 m along thvu uuf0 676ttari;f3ee floor against a friction force of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (horizontally)q- rmbl/9zda 7 pushing a 160-kg crate 10.3 m across a rough floor without acceler abl d/zq-m79ration, if the effective coefficient of friction was 0.50?    J

  A box of mass 5.0 kg is accelerated by a fl8b4q i k:tm -*wdz56 4sivqnmorce across a floor at a rate of for 7.0 ib*m-l4 6n k5qmqw4td: 8visz s. Find the net work done on the box.   J

  Eight books, each 4.3 cm thick with mass 1.7 kg, l:2rfsno,yxbn1 pqleb 03k t14ie flat on a table. How much work is required to stack them orltk4:1b s10efyq 3o2,xpnb nne on top of another?    J

A lever such as that shown in Fig. 6-35 can be used to ak e cgi 1 ulfd++4512gx g:z *srob4lif(1gymliff objects we might not otherwise be able to liff. Show that the ratii15+rezy ib1+lkxs4fcug2mg g(og: fl 4da1* o of output force, $F_{\mathrm{O}}$, to input force, $F_{\mathrm{I}}$, is related to the lengths $\iota_\mathrm{I}$ and $\iota_\mathrm{o}$ from the pivot point by $F_{\mathrm{O}}/F_{\mathrm{I}}=l_{\mathrm{I}}/l_{\mathrm{O}}$ (ignoring friction and the mass of the lever), given that the work output equals work input.

  A 330-kg piano slides 3.6 m down a 28° incline and is kept from azw*p wy(dhk25yr*7p l ccelerating by a man who is pushing back on i*h2w7y5ldzky( r* pw pt 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 uch ;r*5 5ftqwscs3;ha helicopter of mass M an acceleration of 0.10 wct;c3 hqs5 *;sr5hfu g upward.    Mg
(b) Find the work done by this force as the helicopter moves a distance h upward.    Mgh

  $\text{What is the minimum work needed to push a 950-kg car 810 m up along a 9.0$^{\circ} $ incline? }$$(a)\text{ Ignore friction. }$    J
$(b)\\\text{Assume the effective coefficient of friction retarding the car is }0.25.$    J

  In Fig. 6-6a, assume the distance axis is linear and that bu7kq(fr;f x26o0xw 5keo;qm $d_{\mathrm{A}}=10.0$ 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, variesn p u5ax:o:x3f as shown in Fig. 6–37. Determine the work done by thix5of :x3nuap:s 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 acts in r vvarvnvz/ f969g ;t7,umq:dthe $+x$ 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, witcf8 3z.+-laitchbzy61qw mc*d/b he . h 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 ar4bb zw51 xs:rxrow is doubled, 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*t 1xfrqw .qk0 stop an electron $\left(m=9.11\times10^{-31}\mathrm{~kg}\right)$ which is moving with a speed of$1. 90\times 10^{6}\mathbf{m/ s}$ ? $\boxed{a\times10^{b} \mathrm{J}}$ a =    b =   

  How much work must be done to stop a 12505pqo8k ;xi-;j/jcth d -kgcar traveling at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from i:b*azr8zq24j )nz ooa bow whose string exerts an average force of 110 N on the arrow over a distance of 78 cm. What 8:zabzzoqri*)4oj n2 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 baup k(b pg*;t/cckward 25 cm when the ball is caught. What was the average force exerted by the t( /;*bgpcku pball on the glove?    N

If the speed of a car is increased f;4h/i6tgo444km e 0tuyqitu by 50%, by what factor will its minimum braking distance be increased, asimueo uyh4fti4 0/;64kqtt 4gsuming all else is the same? Ignore the driver’s reaction time.

  At an accident scene on a level rou 2p m6a-6flybad, 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 (a6p6ybu f 2m-alnd 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 By the tpk+ob- wbi5m ) tx)lz9ime it reaches the plate, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resistance during a pitch, if the distance betwp 5)m+blb )9-xowkziteen the plate and the pitcher is about 15 m.    N

  How high will a 1.85-kg rock go if t .vpr-jq99b7zvhbfdd. zd (d 6hrown straight up by someone who does 80.0 J of work on it? Neglect air resistanc z.rvvb d6qz. ddj9hd-b97(pf e.    m

  A 285-kg load is lifted 22.0 m vertically with an acceleration by a singlezqzg80lwpc7fiu*9 wn/t3s 9. 9ewe ul cable. Det 9i3z7p0 * u.lfgcw9w eunz89wsq/eltermine
(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 :lz 2dk8: -r9 pwqe.ihizvc;l 440N/m How much must this spring be stretched to store 25 J of p:erz2:ql-hic k98 plwdiv;z .otential energy?    m

  A 7.0-kg monkey swings from oney t-j soyn52g2qod:n 9 branch to another 1.2 m higher. What is the change in potential energy? n92nqosd5-t j2y go y:   J

  By how much does the gravitational potential energy of a 64-kg pole vaul8kobd m cgex)j* 8e:b(ter change if his cente:b b*mexc( 88k g)deojr of mass rises about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizontal surface has speed5ti ,) 7ipdsez v = 65 km/h when it strikes a horizontal cz7d s 5iei,tp)oiled spring and is brought 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 9 w95dmrjyikra0mv, z*)/,rf xip,zea 2.10-kg book from the ground so it is 2.20 m above t9/9yxwrkjv*)a e i 0mir r,,mpfz 5,dzhe ground. 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 climbs to the top of a pu81q;mjldm +4es y 5s3300-m peak.4 sdmusm5e 8p+;l1yqj
(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 verti hn2mfp-i2i, fcally next to a ruler. The end of the spring is next to the 1nhm2, f ifi-2p5-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 v/t z)ka n ;nvgt3 f6*lv5fz(xaine hanging vertically from*ta/z (fa 53fgl)zxvvn; t6nk a tall tree in the jungle. How high can she swing upward?    m
Does the length of the vine affect your answer? ----待选择----yesno 

  A novice skier, starting fro nvl:*apxf/qs9jf - oc0 ez*-hm 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 frictionle6b77i dou5mdzss 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 p 5p qj)d l7t2dfysbdt8w6+b0 is transformed into gravitational potential energy without the aid of a p) w72s yblp dqb0+f 6jdtp5td8ole. 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 aie 1fj0kf aj*x +us/85pkcfi, rtist jumps vertically upward from the top of a platform with a speed of 5.0 mi81esx/50 ,jk+ipf cff aj*uk /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 mab+ 8flqzgk/n(ss), whose spring stiffness constant is 950N/m is attached to a table a / kf(nl8+zbqgnd is compressed down 0.150 m. (a) What upward speed can it give to a 0.30-kg ball when released?    m/s
(b) How high above its original position (spring compressed) will the ball fly?    m

  A block of mass m slides without frictioy ga 9e*)r/-oetdk8to n along the looped track shown in Fig. 6–39. If the block is to remain on the track, even at the top of t- k/toa)dot9ee*gy 8rhe 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 (springaycu4 5bb5 c5 vc:8odw stiffness constant k), Fig. 6–40. The block is given an initial displacemecy va8cu4c5 :obw5d 5bnt $x_0$ after which it oscillates back and forth. Write a formula for the total mechanical energy (ignore friction and the mass of the spring) in terms of $x_0$ position x, and speed

  A 62-kg bungee jumper jumps from a bridge. She is tied to a bun.7pm th szh;i;gee cord whose unstretched length is 12 m, and falls a total of 31 m. (a) Calculate the spring stiffness .hz ;spti7;mhconstant 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.*u/*m* tl x:jb/xdh :xjiybnv9 8uya 1 where it is released from /* m *uxj *:b ytuxv8x.lna9bjhdi:y/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 5db2b.crsl j;o* fy/f at an angle of 33 $^{\circ} $. (a) What is its speed at its highest point    m/s
(b) how high does it go? (Use conservation of energy, and ignore air resistance.)   m

An engineer is designing a spring to be placed at the b pprb41eools8il3ph swee ,6v/21 - tbottom 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 total mass of the elevator and pas-b 2po1bwpep, re6ssthov1e/3il8l 4 sengers.

  A cyclist intends to cycle up a 9 xwq5gz9b ydcp :tye (yy2)4r7.8 $^{\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 opposons8y 6qtpv:i2w +zs 3ite directions, collide headsvs6t8pzoq3 yw +2n:i-on and come to rest. How much thermal energy is produced in this collision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slide 3.5 m high and reax.;tui5w/8 6rryy+ e p4pwi*v8, wv7 b rvwdsjches the bottom with a speed of 2.2m/s How much the /85 ujwib6dv;ep w.p s7,twy *4+rr rv8wxyvirmal energy due to friction was generated in this process?    J

  A ski starts from rest and slide waen8r*6 1dm g p-syyj6eni,1s 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 6)qd- yd(w vrb13.0 m above the ground.
(a) With what speed would it hit the ground if air resistance could be ignored?    m/s
(b) If it actually hits the ground with a speed of 8m/s what is the average force of air resistance exerted on it?    N

  You drop a ball from a height of 2.0 m, and ixpb+n 4 m(l luvqg .7v2q /tp/a8oo*iyt bounces back to a height of 1.5 m.pv +im*v/q8 q(uo xlb7ola 2.ny/t4pg
(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, startg;vt63ijo6px rcheob*r qyvn :7 5,b:ing from rest, is pulled across a floor with a constant horizontal force of 350 N. For the first 15 m the floor is frictionless, and for the next 15 m the coefficient of friction is 0.30. What is the final speed of6ob5: yjvp6ohri gvb3nq ex;rc, *7 :t the crate?    m/s

  Suppose the roller coaster in Fig. 6–41 passes point 1s48hybcs:8bv;aif 4z/*l bog with a speed of If the a;y:/a8s*vih4lgbbz cb84 fos verage force of friction is equal to one-fifth of its weight, with what speed will it reach point 2? The distance traveled is 45.0 m. $\approx$    m/s

  A skier traveling 12m/s reaches the foot of a 6/u)lxmysr-9y(t g3jz izom4 steady upward 18.0 $^{\circ} $ incline and glides 12.2 m up along this slope before coming to rest. What was the average coefficient of friction?   

  A 0.620-kg wood block is firmly attached to a very light horizontal spring (k=183s iy)hzv tnv788 l/ng0N/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 fr3/8zl s7v)nn8ght viyiction between the block and the table?   

  A 280-g wood block is firmly attached to a very light horizontal spring, Fig. 6–u(7m1a.oi yny wy2bj np0b;d /40. The block can slide along a table where the coefficient of friction is 0.30. A fo do0y.p1nmwu2;b bn(y/ay j7i rce 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” (massr j ; 1t 4g07vgmuzen6ez+sk ;uy.ynv4 of 980 kg including pilot) that was launched horizontally at 500km/h f4zung;nz7k ve.64vyt0su rjye+ m; 1grom 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 absence of air resistance?$\approx$    km/h
(b) What was the average force of air resistance exerted on it if it came in at a constant glide of 10 $^{\circ} $ to the Earth?$\approx$    N

  How long will it take a 1750-W motor to lift a 315-kg piano to a sixmsqb3e*d+; uyg +0loa tfk7 a+th-story window 16.0 m above;0 g ue7qt damfsyo3l b+*k+a+?    s

  If a car generates 18 hp when traveli 0f26ez( ayjahng at a steady 88km/h what must be the average force exerted on the car due to friction and air resistance? 0eahzfaj 2y(6    N

  A 1400-kg sports car acceleraox 8 tnt2zz ,x0a4hb-mft8e5 otes from rest to 95km/h in 7.4 s. What is the average power delivered by the eng 45b,tnz8 -eoomz0ta2hfx 8 txine?$\approx$    hp

  (a) Show that one British horsep 2dom4ihh2 5xuower$ \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-zom yn8x 7yam/ 2x8ted4 tru* .aex1(thours.”
(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.*+7dm2 fxxn /h)axk3m- fq1af b3rjpk0 s on the level when it is in neutral. Approximately hd37* -f2m)fk fqx mnka1bx prx/3+ja 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 in1axk ch 10lcf)y)2 ltt 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerax zlsb2+2s*a f bjgo*0tes a 7.3-kg shot from rest to 14m/s If this motion takes 1.5 s, what average power was deveb*l 2szb+oaj2 f0x g*sloped?$\approx$    W

  A pump is to lift 18.0 kg oz h7(gt7y )4ws6 l3kljs u1adt5vp nm9f water per minute through a height of 3.60 m. What output rating (watts) sh1 sl (5pm)kawdutt73yl h76z vnjs9g4ould the pump motor have?    W

  During a workout, the football rhy,sib.0 1 ggplayers at State U. ran up the stadium stairs in 66 s. The stairs are 140 m l, y. 0hgrgs1ibong 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 climb a 60p fvn 7-,*an,c uy;ytlachc).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 12)rp tq-dwv2us imz6+gv9 8ew(0 hp. How steep a hill can it climb at a constant speed of 75km/h if the frictional forces add- z 8(e uri)tp92vmg6wvw+dsq up to 650 N?    $^{\circ} $

  What minimum horsepower must a 533ww3n hi 0kzpmt 4brz0uiyz,wkfc-1z+w9amotor have to be able to drag a 310-kg box along a level floor at a speed of 1.2m/s if the coe w+9z4tkzrw- 030ia3w wykbcui3hmfzn5p1 z,fficient of friction is 0.45?    hp

  A bicyclist coasts down f+ t z9t (abqrq)-7i1fzkn iq;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 hpubzvff +:f.:t85t; i gh)tjkave 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 u:g vjf5p.8 tt:zf;ihb)tf+ k 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 ground,uglb2q7:g aytvns:7w4 ;vkf,jv g .w3 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 af:v 7wgktw 2gj37 :ygqvu,sv4 ;b.nl, 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 shoe4c-nrig4dj8e4z rzc:c,dvp 6 9 feh5ws that his center of mass rose 1.1 m from launch point to the top of the arc. What minimum spee8ncir465cdcg fz4e p: - 9vrjeedhz4,d 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 shvcwu+4kfce02 own in Fig. 6–39 is to remain on the track at all times, e +20fkc4cv uewven 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 ;8.ehpjsc*gs 370 m after jumping from an aircraft without his parachute opening. He landed in a snowbas*g8c ;js eh.pnk, creating a crater 1.1 m deep, but survived with only minor injuries. Assuming the pilot’s mass was 78 kg and his terminal velocity was 35m/s 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 ofp/ssd87jj3l r length L whose other end is fixed (Fig. 6–43).8 rs3dp l/jsj7
(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 m:cv.be -s6 8n*nicdfn ountain. The climb is made in 5.0 h starting at an elevation.6:dbc ncif ve8-n*ns 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 elevkw4f9fe7xcmy eb 2b5 5ator 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 t-aun(j *2oykn9obc8 jhat its lifts can move 47,000 people per hour. If the a(obu8y*a o 9jnn jk-2cverage lift carries people about 200 m (vertically) higher, estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam ag 62ezprlir+z l43m d4no)2(a.ywh 7wrh b:dt t the rate of 650kg/s and falls vertically 81 m before striking the turbine blades. Calcuadt2r4. r4r yn7:)h oz2idh6w3m(l plbzw+gelate
(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 circka dps8hvc .ehm8n +a 8d+6y3gular vertical loop (Fig. 6–44), the difference in your apparent weight at the top of the circular loop and the bottom of the circular loop is 6 g’s — that is, six times your weight. Igndeg a3na.syc6pvhdk hm8+ + 88ore friction. Show also that as long as your speed is above the minimum needed, this answer doesn’t depend on the size of the loop or how fast you go through it.    mg

  (a) If the human body could convert a candy bar dw1 f; j*m6+(+,sn tkvloknqmtirectly into work, how high could an 82-kg man climb a ladder if he weremvqk;fj monl6+t+ t (ksnw1,* 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 an upward a rcdp:reuj4ie*aa1 f ;oyz3f; 0a 8t.wngle 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 insidev3)ndz v1+ oic2x gxcc8-,wx t the scale compresses 0.60 mm, and it tells you your weight is 710 N. Now if n) ,-2izwc83+xxgt xovdc1 vc you jump on the scale from a height of 1.0 m, what does the scale read at its peak?    N

  A 65-kg student runs at 5m/s grabs a rope, and swingsrc7 xnct 81f5t out over a lake (Fig. 6–45). He rele1crt75 ct8 fnxases 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 bi8nk) 2uy:csna+j;4goq.u f4l-gjsclimbs a vertical distance of 5.0 m in 9.0 s. What minimum power output was used to accomia.8;:y)jf+n n oq uu2gkl4bc js4g-splish this feat?    W

  Some electric-power companies use watey5a x l9v1upx( ok89qm s7v6zhr 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 ho1 yxx s7hkmvavu9q68pl5( z9our 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 c 3y4 7f pcqu;5eg6bzubonstant k is cut in half. What is the spring stiffness constant ypb6 g7 efu5;4 qcb3zufor each of the two resulting springs?   k

  A 6.0-kg block is pushjv9x/ y,fpw.tv; *dmped 8.0 m up a rough 37 $^{\circ} $ inclined plane by a horizontal force of 75 N. If the initial speed of the block is 2.2m/s up the plane and a constant kinetic friction force of 25 N opposes the motion, calculate
(a) the initial kinetic energy of the block; $\approx$    J
(b) the work done by the 75-N force; $\approx$    J
(c) the work done by the friction force;    J
(d) the work done by gravity;$\approx$    J
(e) the work done by the normal force;    J
(f) the final kinetic energy of the block.$\approx$    J

  If a 1500-kg car can accelerate from 35km/h to 55km: qsb c:;xgvs4pct(jb )j(50b e pbb.d/h in 3.2 s, how long will it bg0j:s:;p(4cs)bx bv(tbd j.ecp 5bqtake 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 te:jd)wqd0j malqgi4*;yf ku4 b6b1rr3pk :y(dst”), the patient walks on an inclined treadmill (Fig. 6–46). Estimate the power required from a 7 qr3w gq pimy0d4 l:yd kfu:*;64(abrb1kjdj )5-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 upwb ,2 ysbzh+;;go2q5u1mj i:n bkplpf/ard a distance of 500 m, what was its velocity when it left theuqb5/,nbykoisl 1 f2 ;p:;h zmgjp+b2 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 as u1x/+vt(knclrcfn- 6x-kr/ t a rate of 95kg/s (a) If this water wheel is set up to provide electric/(-vsf/ck xrcuk6 x- n1 trln+ity output, what is its maximum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s