In what ways is the word “work” as used in everyday language the shwp wei4:0t*arzh8p7z::hew m* wo o2ame as that defined in physics? In what ways is it different? Give hwt0*w:p ozwhwhr8* 42 ope:ai:z me7examples of both.

Can a centripetal force ever do work on an object? Expla4dvy89mzb ij;q3/xj.t ti7i e in.

Can the normal force on ahdn d1bd3bun (f-+*jgn object ever do work? Explain.

A woman swimming upstream is not moving with respect to the shore. y drzwz,dy 9n4*fzm, vu7c93n Is she doing any work? If she stops swimminczw 7 y3v9z my9u,rndz*f,d4ng and merely floats, is work done on her?

Is the work done by kinetic friction forces wt+( m* lyui:jalways negative? [Hint: Consider what happens to the dishes when you pull a tablecloth ou: my(ul twji+*t from under them.]

Why is it tiring to push hard against rzy0n;;: .qmy fo8no sa solid wall even though you are doing no worky; z0onf n;8. yms:orq?

You have two springs that are identical except that spring l is st8tef wfeind4m0 2(2ph iffer than spring penhm8ef i240wd(2t f 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 is free to slide z;dlz2dm :,b4 v g/ti)q1k sbzon a frictionless surface (Fig.6-30). The block starts from rest at þoint A, and by the time;/blb1dzm,dv s2iz:tk)4 gqz 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 energ ,c);8 z raz3lx3t6vv( dioelxy change when you jump as higho3lldr)v8z6xv zi( 3x a ce;t, as you can?

In Fig. 6–31, water balloons are tosmsmvxgr25 li4 u;p7(jsed from the roof of a building, all with the same speed but with different launch angles. Which one has the highest spe ri;4 (lvg5xm7sju 2pmed on impact? Ignore air resistance.

A pendulum is launched from a point that is akg/:6gv 6a uhr height h above its lowest point in two different ways (Fig. 6–32) v/ru:aghg66k . During both launches, the pendulum is given an initial speed of 3.0m/s On the first launch, the initial velocity of the pendulum is directed upward along the trajectory, and on the second launch it is directed downward along the trajectory. Which launch will cause it to swing the largest angle from the equilibrium position? Explain.

A coil spring of mass m rests upright l)6q7wr gst d)on a table. If you compress the spring by pressing down with your hand and then release it, can the spring leave the 6)tlr7q)gds wtable? Explain, using the law of conservation of energy.

A bowling ball is hung from the ceiling 12lwzf.cmajab g(5k .vsv(q*by a steel wire (Fig. 6–33). The instructor pulls the ball back and stands against the wall with the ball against his nose. Tvcjf a1..(*q ws52mavgzl k b(o avoid injury the instructor is supposed to release the ball without pushing it. Why?

What happens to the gravitational poten 9 qxfh/7/)ws3lo*ug.5gm,pekj zi d btial energy when water at the top of a wabpe /7)fg9.li dk*53hm x,szjou w/gqterfall falls to the pool below?

Describe the energy transformations when a child hops around o3zk:f (fh4bk qgjj-o *n a pogo stick.

Describe the energy transformations that take place when a sk+q:ogsrp kx ,,u1t4lu5 ro;tmier starts skiing down a hill, but after sgtu q41lr+5trkom: u;,p,x oa time is brought to rest by striking a snowdrift.

A child on a sled (total mass m) starts from rest a4i9 7aiwj)c tceb6d2 ft 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) there is fricti2764jib faicdctew9) on (deep snow)?

Seasoned hikers prefer to step over a fallen log in their path ratheae:/vhz 0 d7xpzv 9hj;r than stepping on top and jumping dowh0j ; ea7hzzxp/9vd v:n on the other side. Explain.

Two identical arrows, one with twice the speed of the other, are fired into a ba1oc 0 g4kfg.re9nonat c9ox3 /le of hay. Assuming the hay exerts a constant frictional force on the ro.13faognn099c4x k/te ocg arrows, the faster arrow will penetrate how much farther than the slower arrow? Explain.

Analyze the motion of a qm902 mu 8j2vebs9bwisimple swinging pendulum in terms of energy, (a) ignoring friction, and (b) taking friction into account. Expla2wjsmiv2q9u e 8bmb90 in why a grandfather clock has to be wound up.

When a “superball” is dropped, can )tk1yk voqftpm .kwm 794 c/t7it rebound to a height greater than its original hmf/vk y9 t) 7mtwq.c7to4k pk1eight? Explain.

Suppose you lift a suitcase from the floor to e d )yb: huy1:lschpp;1 k:y3da 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 (d) the weight of the suitcasbd:hcupy; y: ys3 d)l1khp1 :ee?

Repeat Question 22 for the power needed rather than d la7u ha00lx*the work.

Why is it easier to chb,k c lezhp4+,b gh(7limb a mountain via a zigzag trail than to climb straight upc hzep, kg7b4b(,hhl+ ?

Recall from Chapter 4,f7/d,avgienda,n :0) ics 49xojxsu * Example 4–14, that you 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, hsevxc7 aa di)/i9sgod:,*f4j nx,n0u ow much rope must be pulled up? Account for this, using energy concepts.

  How much work is done by the gravi- j rp64ymhxao)0ru5ymwp.t:ak3 ad/ tational force when a 265-kg pile driver fallswa3apyo) jx4apm khyu0mr :6 d r.t5-/ 2.80 m?    J

  A 65.0-kg firefighter climbs a flight of stairs 20.0 m higbkc jj(k i,h65:ko8 gvh. How much work is required?ihko8(k:k 5bj,gv jc6    J

  A 1300-N crate rests on th(k 9x;z e.y wlt+f/rcae floor. How much work is required to move it at consta/(.c zxf;rwety9+ ka lnt speed (a) 4.0 m along the floor against a friction force of 230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did thnjm; uh,2uju5e movers do (horizontally) pushing a 160-kg crate 10.3 m across a rough floor without acceleration, if the effective coefficient of friction wan,;juj5mu2hu s 0.50?    J

  A box of mass 5.0 kg is accelerated by a fow5dx7fwrresc* o.15i s:;by l rce across a floor at a rate of for 7.0 s. o.f57xd*1clywrr b5 :;w essiFind the net work done on the box.   J

  Eight books, each 4.3 cm thick with mass 1.7 kg, lie flat on a table. H)ph)qvfo49j h;ivn w/1;g x juow much work is required tq ux4 /igfow; 1v); jnh9hvp)jo stack them one on top of another?    J

A lever such as that shown in Fig. 6-35 can be uqy-3f )n:v qp)x6dvxs s/ai,bx9tl z5sed to liff objects we might not otherwise be able to liff. Show t)fvlsb65v),q dp9 yx:asz x /tiq3nx-hat the ratio of output force, $F_{\mathrm{O}}$, to input force, $F_{\mathrm{I}}$, is related to the lengths $\iota_\mathrm{I}$ and $\iota_\mathrm{o}$ from the pivot point by $F_{\mathrm{O}}/F_{\mathrm{I}}=l_{\mathrm{I}}/l_{\mathrm{O}}$ (ignoring friction and the mass of the lever), given that the work output equals work input.

  A 330-kg piano slides 3.6 m down a 28° incline and is kept from ac ys+;m3 9wdb5 eilb6mlcelerating by a man wy9lm6i3b;+5sme dw lbho is pushing 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 angt dqqi-78j ;a acceleration of 0.10 d-8t jagq; q7ig 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 thatwfzhep+ 1a90 *d *krfh $d_{\mathrm{A}}=10.0$ 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,cueb)i/u6js /5ixwb. *j ze6f varies as shown in Fig. 6–37. Determine the work done by this force to move the object (a) from x=0x b6.cjeif )5jw /iz/u sbe*u6 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 actso9fxtlhv :+qyp9; kocf yk 79t 7qov., in the $+x$ direction. Its magnitude increases linearly from zero at
$x=0$, to 24.0 N at $x=3.0$ m. It remains constant at 24.0 N from $x=3.0$ m and then decreases
linearly to zero at $x=13.0$m. Determine the work done to move the particle from $x=0$ to $x=13.0$ m
graphically by determining the area under the $F_x$ vs. $x$ graph    J

  At room temperature, an oxygen molecul0zr(jaszxmdq+5o n *k 8vl,t4e, 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 shiyc -w 6 5fs8ua( roi(o)b(z j9fft: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 sto7m)(: tnbxqp ;zs4ezsk0sj -wp an electron $\left(m=9.11\times10^{-31}\mathrm{~kg}\right)$ which is moving with a speed of$1. 90\times 10^{6}\mathbf{m/ s}$ ? $\boxed{a\times10^{b} \mathrm{J}}$ a =    b =   

  How much work must be done to stop a 1250-kgcar traveling at 1xjq m) ybw3e4905km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whose string exerts an almtys0j,1sb r -f s4.jverage force of 110 N on the arrow over a distance oy,jslbt4f rs.s-j 1m0 f 78 cm. What is the speed of the arrow as it leaves the bow?    m/s

  A baseball (m=140kg) trnvi3 l33f6 dni .gjf4v gmq2/maveling 32m/s moves a fielder’s glove backward 25 cm when the ball is caught. What was the average force exerted by the g im2g m6jn/3i4f dfv3n3q.lvball on the glove?    N

If the speed of a car is increased by 50%, by what factor will itsytcw/;k5-)r f,jv lixwpn08 z minimum braking distance be increased, assuming all else is the same? Ignore the drivecv z-p ;xtyw5l,/i jnrf) 8kw0r’s reaction time.

  At an accident scene on a level road, investi.om n wnw:1mv+gators measure a car’s skid mark to be 88 m long. The accident occurred on a rainy wn m:+ w.v1nomday, 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 o.yp2qtcj t2 i:f 0.25 kg is pitched 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 q ycj22pt. i:tthe distance between the plate and the pitcher is about 15 m.    N

  How high will a 1.85-kg rock go;bdhv5 l1d 2au if thrown straight up by someone who does 80.0 J of work on it? Neglect air resis a1d2 dlv5hub;tance.    m

  A 285-kg load is lifted 22.0 m vertically with an acceleration by a singl1+lokb)oh-mpy.0r- j1 ci(vp d5 wnt ke cable. Determinoj (05ypiwkod1lh+ -mr1kpt. cbv-n )e
(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 much57t4 x9nw .cdt3dz kpn must this spring be stretched to store 25 J of potentia z35ptt4dn9dx nwk7. cl energy?    m

  A 7.0-kg monkey swings from one branch to another 1.2 m higher. Whato jr;qwue,o2au 14,ja 1w-yoa is the change in potentiuqo,oj ea 4or12a 1w;waj-uy, al energy?    J

  By how much does the gravitational potential energy of a 64-kg pole vaunmn5 itg9g :)glter change if his center of masmg:ginnt )5g 9s rises about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizontal surface has spf.de h7- ,rkm8wngi;u 7 bclmn;wp;.ieed v = 65 km/h when it strikes a horizontal coiled spring and is brought to rest in a distance of 2.2 m. What is the spbgr7di.- p7h ;i8lkm,c;mw;n en.f w uring stiffness constant of the spring?    N/m

  A 1.60-m tall person lifts a 2.10-kg book from the groh 1hdiyh e z;m6kxz,+,+z .yigund so it is 2.20 m above the ground. What is the potent1e,d y z+hzh g.+6;iixmyk, zhial 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 clihvcf0)5v h 5q)5hrt4gbd+uk ombs to the top of a 3300-m pe5)o qfk gbur0h5vhd5v+4)tchak.
(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;q; sw5irjva 0cally next to a ruler. The end of the spring is next to the 15-cm mark on the ruler. If ws5j i0;;rvqaa 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 t /d58 xqhwle5pop speed (5.3m/s) and grabs a vine hanging vertixd5q/5le8 hwp cally from 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 from res2bs-: q:5vtz rhloqz(t, 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 friceo lk7r )s 8wzs7*z8sutionless 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 f;ox2 h,jfhid*sb85 ktransformed into gravitational potential energy without the aid of 5sf2*xk j h,ohbdi ;f8a 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 towz l) m..2tzav jzpuor9*we14p of a platform with a 9 )va4ol2p*z1mz . wujrw.tz espeed of 5.0 m/s. ($\alpha)$ How fast is he going as he lands on the trampoline, 3.0 m below (Fig. 6-38)?$v_2$ $\approx$    m/s
(b) If the trampoline behaves like a spring with spring stiffness constant 6.2×10$^{4}$ N/m , how far does he depress it? $y_3$ =    m

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

  A vertical spring (ignore its ml(fw08wj wa13 z,o,9i ceqjolass), whose spring stiffness constant is 950N/m is attached to a table and is compressed d li9q zf,wj,013wjac8wl o( oeown 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 slf3du9d jkop, v2vtomy2cz4,(ides without friction along the looped track shown in Fig. 6–39. If the block icyu v,zm( 3fd ,9koj2t4ov2pds to remain on the 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 (spring stiffness constanfp9z3 o; 8/urpbt9ik-kl 4civ* ym a*et k), Fig. 6–40. The block is given an initial displacement l8kkf9b i-e m9ti u/cz3y4p*; *ovpra$x_0$ 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 ajkqs7u8m rwl /)xsfq 0* r9ai4 bungee cord whose uns7rj/l0qf8 49m ) ia*xqwru skstretched 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 applies. $\approx$    N/m
(b) Calculate the maximum acceleration she experiences. $\approx$   m/$s^2$

  The roller-coaster car shown in Fig. 6–41 isg9t rrd-5eu 4f9j*znn dragged up to point 1 where it is released from rfneg9u5drtz-4r*n 9 jest. 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 oe98y gu) x,tdjf 12 m/s at an angle of 33 $^{\circ} $. (a) What is its speed at its highest point    m/s
(b) how high does it go? (Use conservation of energy, and ignore air resistance.)   m

An engineer is designing a spring to be,mvch qoo6-j2.- zv r5vjax/ a 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, 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 th,5/a6v.q2rvojm oa- j-h cvx ze elevator and passengers.

  A cyclist intends to cycle up a 7j0+q/(ggk2e ncp7 pe 2nqfc ,j.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 9.st92deq q8k* ovl j(i5km/h in opposite directions, collide head-on and come to rest. How much thermal energy ikde 2( t8v.oq l*s9jqis produced in this collision? $a\times10^b$ J a =    b =   

  A 21.7-kg child descends a slide 3.5 m high and reaches the bottom w8n32u, o. 4e auib1po *oxdzjbith a speed of 2.2m/s How much thermal energy u o.*aoi x1 j ob42ezdp,3nb8udue to friction was generated in this process?    J

  A ski starts from rest and slides dow)hv+ omgg7 s nm.b9u,lc5ftlz:+im,s*ag f;yn 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 1op zxsocv sjtu;/9f 1()s56o q3.0 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 it bou:m.jkdl bi qgtx +058af8 fi7 +wlmkf6nces back to a height of 1.5 m..jq+xfm5f7w: it6+lk8m0 fd igabk 8l
(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 aco r)xhco bir+u ;24e:yross a floor with a constant horizontal force of 350 N. For the first 15 m the floor is frictionless, ao2yxh;cr+u ) b:ire4o nd for the next 15 m the coefficient of friction is 0.30. What is the final speed of the crate?    m/s

  Suppose the roller coaster in Fig. 6–41 passes point 1 with a speed of If theisxg86zb,,rb *( apw c average force of friction is equal to one-fifth of its wz(asg,i6p b x8c,w*br eight, 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 csrc7kivb zyf ;3u,lq/(z2az5d m4f4 of a steady upward 18.0 $^{\circ} $ incline and glides 12.2 m up along this slope before coming to rest. What was the average coefficient of friction?   

  A 0.620-kg wood block is firmly attached to a very nh3k ivj (7y45,g6btcnlfma*light horizontal spring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compressed 5.0 cm and released, stretches out 2.3 cm beyond the equilibrium position before stopping and turning back. What is th,j5 n*6bikhm y3cnt7gv l4(fae coefficient of kinetic friction between the block and the table?   

  A 280-g wood block is firmly attached to a very light horizonby */p qahvpv3d1 02tltal 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 ita13pt/hpv*2 dqv l by0s first swing?    m

  Early test flights for the space shuttle used a “glider(8t1hub1 sp ah-x4ny j” (mass of 980 kg including pilot) that was launched horizontally at 500km/h from a height of 3500 m. The glider eventually landed at a speed of 200km/h (a) What would its landing speed have been in1h j-1hy unx8b(a s4tp 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 ax01 4ua4e fq -q0epyfm 1750-W motor to lift a 315-kg piano to a sixth-story window 16.0 m above? ee14fp0q4a u- xmq0yf   s

  If a car generates 18 hp when traveling at a steady 88km/h what ma m e68lq2b8ffye. 5z-2rzslnust be the average force exerted on the car due to friction and air resistance? -m8nel2z8fsb lzqf2y aer.5 6   N

  A 1400-kg sports car accej0r bc6v40fs ez 7w06lxtypi. lerates from rest to 95km/h in 7.4 s. What is the average p7er00c z j 60blivy.6f4wtsxpower delivered by the engine?$\approx$    hp

  (a) Show that one British horsepower;hpc + wgta*)x$ \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 unitywai3b*t 7og7jxt 7c-eea; o* s are often expressed in the form of “kilowatt-hours.”
(a) Show that one kilowatt-hour (kWh) is equal to $3.6\times10^6$J
(b) If a typical family of four uses electric energy at an average rate of 520 W, how many kWh would their electric bill be for one month $\approx$   kW*h
(c) how many joules would this be?$a\times10^b$ J a =    b =   
(d) At a cost of 0.12 dollars per kWh, what would their monthly bill be in dollars? Does the monthly bill depend on the rate at which they use the electric energy?    dollars

  A driver notices that her 1150-kg carn )u92 +wfjc mrbmk23cd9wv.p slows down from to 65km/h in about 6.0 s on the level when it is in neutral. Approximately what power (watts and hp) is needed to keep thc3nm2jd wpk.) vb9cuwrm2+f9 e car traveling at a constant 75km/h.    hp

  How much work can a 3.0-hp5 nrguh)+ nqp p-oz1l; motor do in 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates a 7.3-kg shot from rest to 14i1 *j owcs6fi9m/s If this motion takes 1.oc*i fj9 i16ws5 s, what average power was developed?$\approx$    W

  A pump is to lift 18.0 kg ofvkp.hdu o;qe4x:1u1kc4wu .z water per minute through a height of 3.60 m. What output rating (watts) should theh.x1.cv eu d4wp ukkuo:q14;z pump motor have?    W

  During a workout, the +l uhd2yv8p f s6j5qv(football players at State U. ran up the stadium stairs in 66 s. The stairs are 1d58yu( j2 +vqphsf6 vl40 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 s *e-:8b1fkicoa o/ewclimb a 6.0 $^{\circ} $ hill to maintain a power output of 0.25 hp? Neglect work done by friction, and assume the mass of cyclist plus bicycle is 68 kg.   m/s

  A 1200-kg car has a maximum power output of 120 hp. How steep a hr jn:hsg m4cn)pr07 j8ill can it climb at a cr nr4j hc7 pgn)m0s:j8onstant speed of 75km/h if the frictional forces add up to 650 N?    $^{\circ} $

  What minimum horsepower must abb2z,b)5d uovc4o t (r motor have to be able to drag a 310-kg box along a le4b)oc2u (,5z votdbbr vel floor at a speed of 1.2m/s if the coefficient of friction is 0.45?    hp

  A bicyclist coasts dow)andz-u;yd-ca i r8j 8n 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) bumbx.9 0* ij3ey nvhv2odpers” that are designed to compress and rebound elastica i39.xo2 yh*0bejvn vdlly without any physical damage at speeds below 8km/h If the material of the bumpers permanently deforms after a compression of 1.5 cm, but remains like an elastic spring up to that point, what must the effective spring stiffness constant of the bumper be, assuming the car has a mass of 1300 kg and is tested by ramming into a solid wall? $a\times10^b$ N/m a =    b =   

  In a certain library the first shelf is)qv3t2a;qknhvl z.jmu46z a (q3 a 4dw 10.0 cm off the ground, and the remaining four shelves are each spaced 30.0 cm above thejv.z2alqq aa n4m3k zt u)w6dh4(q3v; 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 Owen;tk o9+ph6xjfs’s famous long jump (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 d9khfpt ;6ox+ jid 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 track7qapi0d6sgw 8-stei jo -,jg-r pr0zmf (5rk0 shown in Fig. 6–39 is to remain on the track at all times, even at the very top of the loop of radfiq 507 pj swi-,-tz80m0d jrrggpoaer(6s -kius 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 .t+1o v8v +chpqlzhqibx -0vt7i6 7y0evim (oparachute opening. He landed in a snowbank, creating a crater 1.1 m deep, but survived+-1ihvv(oqe bo00+ . t8 hvxtliz7 6c7 vqmyip 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 t(ni pevu-rxtgvj: vw):b(6)zo a horizontal cord of length L whose other end is fixed (Fig. 6–43n6:b (gtu(p:ivj -zxrv))e vw).
(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 39rp(n gq /ghcml8a/(m 700-m-high mountain. The climb is made in 5.0 h starting at an elevation of 2300 mc98/(g/hpmg (nmqlr a. 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 9l9 /k(pdby)wx 20-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 move 47za- c3x,7gsq.cn no ly-g1im1,000 people per hour. If the average lift carries people about 200 m (vertically) higher,mn- 3ao,zq1y 1xisg7- g c.nlc estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam at the rate of 650kg/s and falls vertically 81 m befor wm+-3a5io vfx/4pnm oe striking the turbine blades iw5m ox 4va-/mn3fpo+. 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 0*sit(pw1gw / v kh95u/bowrk coaster with a circular 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, sigurh(s*i/k/0 o9vwkp wt5w b1x 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 size of the loop or how fast you go through it.    mg

  (a) If the human body could convert a candy 6 xnd tkh)* qvv+kpmv.17gjfj;zsd: :bar directly into work, how high could an 82-kg man climb a ladder if he were fueled by one bar .:* 7tv+:d)kg sdzvjpk f6;1mn xq vjh(=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 of::8mi 5 clbxmdehzy74p . vr7k 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 scal-z(s 70co),nlrdjt n*yf v,mle compresses 0.60 mm, and it tells you your weight is 710 N. Now if you jump on the scale from a he,td rlf)zcl-7* jmv0sn,(onyight 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 swings out over a lake (Fig. 67pd +p,hwvo73 o k2bpe k jjiucp+6d3/–45). He releases the rope whe6pk7oo/+bjv,d wp2 j cd7p k3h3e+u pin his velocity is zero.
(a) What is the angle when he releases the rope?    $^{\circ} $
(b) What is the tension in the rope just before he releases it?    N
(c) What is the maximum tension in the rope?    N

  In the rope climb, a 72-kg athlete climbs a vertical distance of 5yp53n*y jatdg8p j o8*.0 m in 9.0 s. What minimum power output waj* n8p5d*ag3yjyot8ps used to accomplish this feat?    W

  Some electric-power companiyxsfd(*,d+tklne -v c7 nc /3xes use water to store energy. Water is pumped by reversible turbine pumps from a low to a high reservoir. To sxt en(* 7/c-s yxckn3d+ vfld,tore the energy produced in 1.0 hour by a 120-MW ($120\times10^{6}$W) electric-power plant, how many cubic meters of water will have to be pumped from the lower to the upper reservoir? Assume the upper reservoir is 520 m above the lower and we can neglect the small change in depths within each. Water has a mass of 1000 kg for every 1$m^3$.    $m^3$

  A spring with spring stiffness constant k is cut in half. What is thewr 0wb+lc4.zd,og mws 0iq4-n spring stiffness constant for each of the two resulting4s,gwb0dzn.0moi w-qw+4r l c springs?   k

  A 6.0-kg block is pushed 8.0 m up a rough 37 l0+yf9x eneevv4xqc9 p 3bs +($^{\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 vz yfs )-xq171rti8ua/h in 3.2 s, how long will it take to accelerate from 55km/htqu-x1 fa7yivr) 8zs 1 to 75km/h Assume the power stays the same, and neglect frictional losses.    s

  In a common test for cardiac3 ,t;huage f9gw1b 7qc function (the “stress test”), the patient walks on an inclined treadmill (Fig. 6–46). Estimate the power required from a 75-kg patient when the treadmill g1,h9gt7 wq e;ba3cfuis 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-kgi-7q te/vw gz; h3rpe: rock vertically upward a distance of 500 m, what was its velocity when it left the volcano? 7tqiez3;:ve / -rwg ph $\approx$    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 watev z +3d/n,k-.f21yl wcwkqbr gr wheel from a height of 2.0 m at a rate of 95kg/s (a) If this water wheel is set up to provide2y/kl vqr,w+n gfzb31.cw-kd electricity output, what is its maximum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s