In what ways is the wordc1yk7 mt e 3knr bzl ,f*i9j-mvi/-a2d “work” as used in everyday language the same as that defined in physics? In whatzv ma, -7niy9ift 1k3*/j-bm k2ecr dl ways is it different? Give examples of both.

Can a centripetal force eveoh )(hs+-ozppaba* df6gfy, ,r do work on an object? Explain.

Can the normal force on an object ever do work? Expl1nx * ;etuy1c8 p(u3c9hruesqain.

A woman swimming upstream is not moving with respect to the shoreeqdmz:1+oz + t. Is she doing any work? If she stops swimmingdz +1:+mq ezot and merely floats, is work done on her?

Is the work done by kinetic friction forces always negativec+* d*dcu9r ku /gp6rd/3 1r:ax pqrwd? [Hint: Consider what happens to the gp9c pqru r/:cuddrar / *w+xk3dd61* dishes when you pull a tablecloth out from under them.]

Why is it tiring to push hard against a solid wall ev6hdxne 5t n,lx0d3zj:hp)h y,en though you are doing no wenty,)hl,5d z3x 0hnp6hj:dxork?

You have two springs that are identical except that spring l is stiffes9 aady1kn6.6dmh 3ekr than spr693d6aknsk e am1h.yding 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 fr/g om4ux6vak2 (k6n 63lwesswee to slide on a frictionlesa(6x34 v eww losg6 kku62s/mns surface (Fig.6-30). The block starts from rest at þoint A, and by the time it has traveled a distance $d$ to point B it is traveling withe bint $o$ point B it is traveling with speed $\nu_\mathrm{B}$.When the block has traveled another distance $d$ to point C, will its speed be greater than, less than, or equal to 2$\nu_\mathrm{B}$? Explain your reasoning

By approximately how much does your gravitational potential energy change when y5sni.t pil( rn.xjy;3ou jump as highs3it( .n5.j nliy;p xr as you can?

In Fig. 6–31, water ball*el jz e +*gn8xe-*cwnoons are tossed from the roof of a building, all with the same speed but with different launchee- *glw+en*zcxj8n* angles. Which one has the highest speed on impact? Ignore air resistance.

A pendulum is launched from a point that is a height h above its lowest point in*8 h wmm7 wuna-caazp. j5a91r 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 m8r* w5a7z-haam nucwj.1 p9a 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 compresq,df g(y6kvxjwwp wl609a 6 sb1,sm ,xs the spring by pressing down with your hand and then relb sld a9myk(,gw0w6 ,w6,xvx p1sf qj6ease it, can the spring leave the table? Explain, using the law of conservation of energy.

A bowling ball is hung from the ceiling b gs1up-*m qpo5y 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 injurypug*so1 5 -pqm the instructor is supposed to release the ball without pushing it. Why?

What happens to the gravitational potential energy whene 91qj.t-qe np water at the top of a waterfall falls to the pool belowtenpe-q qj 1.9?

Describe the energy transformations when a child r(3fde ein;e),fs1 sm ge 44dchops around on a pogo stick.

Describe the energy transformations that take place when a /w4l. xg8.rnld-im kgpxct38 skier starts skiing down a hill, but after g4x.xc8. 8/t k-3nidm lwrglpa time is brought to rest by striking a snowdrift.

A child on a sled (total mass m) starts fagx 8msludtq8-)w0 f)rom 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, asfxt 0mu 8dql8w)-ga )nd (b) there is friction (deep snow)?

Seasoned hikers prefer to step over a fallen log in their path rather than stepc/otv 341z uuzping on top and jumping down onc 1z34 ovu/uzt the other side. Explain.

Two identical arrows,ae8zl-o ju0-lki ic xss. 2-6c one with twice the speed of the other, are fired into a bale of hay. Assuming the hay exerts a constantkiauz6j-0 -llsise c. xo8- 2c frictional force on the arrows, the faster arrow will penetrate how much farther than the slower arrow? Explain.

Analyze the motion of a simple swinging pendulum in terms of energy,cmr-dcl9 ):4 z; ew r82iljtmv (a) ignoring friction, and (b) taking frictiom; lr d)m9284wev-:cjzcrli tn into account. Explain why a grandfather clock has to be wound up.

When a “superball” is dropped, can it mlw4akd5hk9/l+n co 8j rt5y6rebound to a height greater than its original height /my cn4lhk r9da+lt8o5 wj5k6? Explain.

Suppose you lift a suitcase from the floor to a table. The work yolol* be+uo p--n,w ms4p1fm *ou 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* l loo ewn,*o4sp u--mp+mb1f, (c) the height of the table, and (d) the weight of the suitcase?

Repeat Question 22 for the power neen ()f,*znshl gded rather than the work.

Why is it easier to climb a mountain via a zigzag trail than to climb straight daiyjsw tibg+*w)zt:; 2k: a0.oy/trup?wbd;t + t0gj ikya/zyowr:)i*: 2.tas

Recall from Chapter 4, nu )fl//1ecqvqj5*gu 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, how much rope must be pulled up? j ql 5/ 1/)efvqugu*ncAccount for this, using energy concepts.

  How much work is done bykv *53buq3k vy the gravitational force when a 265-kg pile driver falls 2.k* vqykb3v 5u380 m?    J

  A 65.0-kg firefighter climbs56yu*rtn +ti w a flight of stairs 20.0 m high. How much work is requi+t65inyutrw *red?    J

  A 1300-N crate rests on the floor. How much work is required to move it at consthottt,cl g 54-ant speed (a) 4.0 m4,toltc g-5ht 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 (bghgp gr1p ;;d/efz ivrh3d 9+l+6,rthorizontally) pushing a 160-kg crate 10.3 m across a rg96vrt;hg+/; d3 +bgl,pr frpid e z1hough floor without acceleration, if the effective coefficient of friction was 0.50?    J

  A box of mass 5.0 kg is accelerated by a force adg141.gf si( 0a:e udmpwbvp*cross a floor at a rate of for 7.0 s. Find the netu. d mei wv(4p0g1 pg*fa:db1s work done on the box.   J

  Eight books, each 4.3 cm thick with c ip4 (zvt4tt.fk:z vd162nezmass 1.7 kg, lie flat on a table. How much work is required to stack them one on top of an4 e(f2t ti6tzpd.zv4nkz1v:c other?    J

A lever such as that h*g9c ra*1gzmshown in Fig. 6-35 can be used to liff objects we might not otherwise be able to liff. Show that the ratio of output forczgg1m 9 *ach*re, $F_{\mathrm{O}}$, 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 2,en0wuofdp *mqp*5r:; w.p p h8° incline and is kept from accelerating by a man who is pushing back on it parallel to ,m5u. op 0ep*nw w;hfrp* :qpdthe 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 a3+8jem6 k4i gz dejryo3 amu,/cceleration of 0.10 g upward. j zi3amoe+r ykeu6m8j3g/ d4,   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, assumen s-7d324ae a afxidg, the distance axis is linear and that $d_{\mathrm{A}}=10.0$ m and $d_{\mathrm{B}}=35.0$m. Estimate the work
done by force $F$ in moving a 2.80-kg object from $d_\mathrm{A}$ to $d_\mathrm{B}$   J

  The force on an object, acting along the x axis, varies as shown in Fig. 6–37y 8 yq/nidep*,. Determine the work done by this force to mov,8y i/qd*n peye 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 t;h*vr41(mabm i scx04azyey5 he $+x$ 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 oxygenj1pgysp9 7*(yf*qp cyldb)n j( h9/ti 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, be:hi 5w7yfp )y7zi+cyy 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 stop an 3bhyi) )4uvk y0g;oq f lih-r: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-kgmcgit :xacrdh+f+. l,/.r-d+td7sj mcar traveling at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whose string exerb. 5qyo7 0gbmkts an average force of 110 N on the0ok 57mb.ygqb arrow 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/.q98x9 1c uw piw,vwmws moves a fielder’s glove backward 25 cm when the ball is caught. What was mw9v.c1 uw9 wip8,qxw the average force exerted by the ball on the glove?    N

If the speed of a car isguoa7,r5zy(( ppowr9 increased by 50%, by what factor will its minimum braking distance be increased, ar (u(zgw po,5opa7 9yrssuming all else is the same? Ignore the driver’s reaction time.

  At an accident scene on a lr57vy*w3 vd gjevel road, investigators measure a car’s skid mark to be 88 m long. The accident occurred on a rainy day, and the coefficient ov y*7rj3 v5wgdf 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 By the tf y-/:y 3u0r+ ouadagcime it reaches the plate, it may have slowed by 10%. Negle+ucr-gy3/a0o :fdy aucting 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 tytd3q o l9a6-dhrown straight up by someone who does 80.0 J of work on it? Neglt o9ydaq-dl63 ect air resistance.    m

  A 285-kg load is lifted 22.0 m vertically with an accbkl4),a8l * anvur3nmeleration by a single cabll)a 3*kv4nb,m ualrn 8e. Determine
(a) the tension in the cable,    N
(b) the net work done on the load,    J
(c) the work done by the cable on the load,    J
(d) the work done by gravity on the load,    J
(e) the final speed of the load assuming it started from rest.    m/s

  A spring has a spring stiffness *z mkg+4 +vfr2w- teyyconstant, k, of 440N/m How much must this spring be stretched to sto tz-4g wfvkemy+*+yr2re 25 J of potential energy?    m

  A 7.0-kg monkey swings from one branch to another 1.2 m higher. What pjxd*6vcy4 p7vznew /16:v mpis the change in potential energ xe*j 7z:61v/ 4nmwv6pdpcyp vy?    J

  By how much does the gravitational potentiaov2qae5epn4um h ;5(ml energy of a 64-kg pole vaulter change if his center of mass rises about 4.0 m dur;qen(5v 4ou 5hamp e2ming the jump?    J

  A 1200-kg car rolling on a horizontal surface has ju41j e(jcdsje/v z (a2me5 )gspeed v = 65 km/h when it strikes a horizontal coiled spring and is brought t2(mz1j4u5eec j /ge v)ds(ajjo rest in a distance of 2.2 m. What is the spring stiffness constant of the spring?    N/m

  A 1.60-m tall person lifts a 2.10-kg book from the ground so if:g f8d j7-k4fipcch5t is 2.20 m above the ground. What is the potential :i cfchf -f7 dj5gp4k8energy 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 ofzn3;pb kh*i1e 1600 m and climbs to the top of a 3300-m peakz13e ibh;nk *p.
(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 to a ruler. T cao b2--lr/nx,csy5bhe end of the spring is next to the 15-cm mark on the ruler. If a 2.5-kg mass is now attached lca/b,x-sb5 -c roy2nto 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) ae- tbm + qt2eg )z 8lh(6ase+;jdipk(ond grabs a vine hanging vertically from a tall tree in the jungle. i le;++-tqd)(2oj8k s(6aepgb z mhetHow high can she swing upward?    m
Does the length of the vine affect your answer? ----待选择----yesno 

  A novice skier, starting from rest, slides down nhpby* v5urp03t bd25 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 ain3f5i;dz u.x201msswhro3h0ecy: b 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 i x(0q+ynbi. ml)-rrqls transformed into gravitational potential energy without the aid of a pole. With what minimum speed must Fran leave the groun qlxq-mbir+ly(r0 ).n d in order to lift her center of mass 2.10 m and cross the bar with a speed of 0.7m/s.    m/s

  A 65-kg trampoline artist jumps vertically upward from the top of a platpu9xu ruc):w:43k( c llz+)ehr 5ppqe form with a sppurplpu 3lekx: )4 5ec+u 9rhwz :)qc(eed 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 mass), whose spring stiffnesshre2)eu*f b )t constant is 950N/m is attached to a table and is compressed dowf *te)hu2er b)n 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 friction along the loo*:t9wumh1e. 6q w gkjzped track shown in Fig. 6–39. If the block is to re6:j*wkhe w.m 1 utzg9qmain 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 t mlh: *j(b iud0q4hd8bj: p,tko the end of a spring (spring stiffness constant k)i*lp b: hh,0m(: bdud8j q4tkj, Fig. 6–40. The block is given an initial displacement $x_0$ after which it oscillates back and forth. Write a formula for the total mechanical energy (ignore friction and the mass of the spring) in terms of $x_0$ position x, and speed

  A 62-kg bungee jumper jumps from a bridge. She qzta7on-e.y1 is tied to a bungee cord whose unstretched length is 12 m, and falls a total of 31 m. (a) Calculate theqazy1-ton 7e . spring stiffness constant k of the bungee cord, assuming Hooke’s law applies. $\approx$    N/m
(b) Calculate the maximum acceleration she experiences. $\approx$   m/$s^2$

  The roller-coaster car shown in Fig. 6–41 is dragged up to po2z v)dtlb1 mb*nk+- veint 1 where it is released dlt)e2mvbz v-n +1b k*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 c ,z :mr;qrzeztpso vs0+,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 placet (ul32t l sue*nq.v)rp(p,azd 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 con,puz(vs eln)p u(tt a.q2lr 3*stant 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 cyg, )pn (ipisq8cle 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 mass 7650 kg and traveling u;h ,woofu g,y:- gr1y95km/h in opposite directions, collide head-on and come to rest. How much thermal energy ish-;ouug,rf: ygwo1y, 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 with 6d7ir((yziu 3 m4uozp)+xyl u ej3i: oa speed of 2.2m/s How much thermal energy due tz(r o(io6xe7y3:y)lm3pj+iuiu z du4o friction was generated in this process?    J

  A ski starts from rest and slidnuwp,f kc *6f6es 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 droppmd2/dr-n.3u r,3unwt- dyjpy ed from a tree 13.0 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 bounces back to a height osgy.j2k::g q sf 1.5 m.j g 2qy.gs::ks
(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 wap0 e- yvhxp4o75kbbt 2w7jw5ith a constant horizontal force of 350 N. For the first 15 m the floor is frictionless, and for the next 15 m tjp-x4bh w7k0eoyavp b57t2w5he coefficient of friction is 0.30. What is the final speed of the crate?    m/s

  Suppose the roller coaster in sbop 0(r1x3cl e 2*o qzs8r*msFig. 6–41 passes point 1 with a speed of If the average force 3pbs1m oclz0s(qe r2sor8 x**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 steady upward 18.:nieaff h.g 8 tg)o o(kkjb3,)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 al.k 1k,86z)xj:9ibu luqamq)3 yzgfsou y80xttached to a very light horizontal spring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compressed 5.0 cm and released, stretches out 2.3 cm beyond the equilibrium position before stopping and turning back. What is the coefficient of kinetic friction betweeuyu kouk0 a3,9is:1qjl)z86xq lfmy8 z.)bxgn the block and the table?   

  A 280-g wood block is firmly attache( -bn6fxtsl;c 6n dah88s /uhrd to a very light horizontal spring, Fig. 6–40. The block can slide along a table where the coefficient of friction is 0.30. A force of 22 N compresses the spring x8hu86al;sr6-c fn bnsht/ d( 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 foa lvy8 cck d*./nht;ivu71sr1 r the space shuttle used a “glider” (mass of 980 kg including pilot) that was launched horizontally at 500km/h from a height of 3500 m. The 7tcic;8 sh r/*nyvav d.ul 1k1glider 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-Wor d 8jrd2pjm ah9h,:3 motor to lift a 315-kg piano to a sixth-story window 16.0 m above?m,j9hdr82o3h d p r:aj    s

  If a car generates 18 hp when traveling at a steady 88km/h what mu+3tww kh7w ww,e8 1 wpbjow(r9st be the average force exerted on the car due to friction +w8jkr,ewp b( w tw3o1 ww7h9wand air resistance?    N

  A 1400-kg sports car accelerates from rest to 915zww cl6o s-kkcparp +;(7th5km/h in 7.4 s. What is the average power delivered by the o z akc1 s +r-wct6;wpp5kl(h7engine?$\approx$    hp

  (a) Show that one Bri jjje xwli9t3(3cfi*6tish 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 of “kcc og yoa(5p dy/oyoi7z9,t2.(ufp *uilowatt-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 6.0nr dg3,ak .e:f*wd4gt s on the level when it is in neutral. Approximately what power (watts and hp) is needed to keep the car traveling at agrnkg*d4.da et,w3f: constant 75km/h.    hp

  How much work can a 3.0-hkzailo1udv x 2 /me)us7e6;2a p motor do in 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates a 5:gu0r5 b n0kydoket: 7.3-kg shot from rest to 14m/s If this motion takes 1.5 s, whatkr:e u0ondt gb55k 0:y average power was developed?$\approx$    W

  A pump is to lift 18.0 kg of water per minute through a height of 3.60 m. What .. fc () (rm3pizvig7xh ola1doutput rating (watts) should the pump motor hav z laio7hgc3r.f (x1p.vi (d)me?    W

  During a workout, the football players x o wvycz),2c7at State U. ran up the stadium stairs in 66 s. The stairs are 140 m long and incl oc cwvyz72,)xined 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 clim18rr ewo:2cz ;awea i9b 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 hill can it cli).gbqy4+qb *radli3mre e ch1do-7e )mb at a constant speed of 75km/h if the frictional forces ade a*qo-re.1 )4g7)lqcdybbe3 irh+mdd up to 650 N?    $^{\circ} $

  What minimum horsepower must a motor have to be able to drag 451yu w0 x 4lo,nh7zjsgp3r inoaduks7/m;n 7a 310-kg box along a level flos izh7rn3lpujnaxkdo4u0o41/7 7wny5g ms; , or at a speed of 1.2m/s if the coefficient of friction is 0.45?    hp

  A bicyclist coasts down a uzuzvg3 u:5shkywj8d :6h v8 y;(6nyj7.0 $^{\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(8k5ih72h6 j ovxp auf);ym/h) bumpers” that are designed to compress and rebound elastically wihf62u);xo7 y h5p ajivthout 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 10.0 cm off the ground, and 5s+oq tqj*hx.8nos0hthe remaining four shelves are each spaced 30.0 cm above the previous one. If the average book has a maso ss05oq8* hhtq+ jx.ns of 1.5 kg with a height of 21 cm, and an average shelf holds 25 books, how much work is required to fill all the shelves, assuming the books are all laying flat on the floor to start? $\approx$    J

  A film of Jesse Owens’s fam4uepord ua6j--i lr-d 6q9gx-ous 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 did he need at launch if he was traveling at 6.5m/s o-dupu6-46erag-xli-rj d q9at the top of the arc?   m/s

  The block of mass m sliding without friction along the looped trzt ;tpb2/4sa5iw 0ksd cr1/fc ack shown in Fig. 6–39 is to remain on the track at 25 014iskpwcb/tza s t/rf d;call times, even at the very top of the loop of radius r.
(a) In terms of the given quantities, determine the minimum release height h (as in Problem 40). Next, if the actual release height is 2h, calculate    r
(b) the normal force exerted by the track at the bottom of the loop,    mg
(c) the normal force exerted by the track at the top of the loop,   mg
(d) the normal force exerted by the track after the block exits the loop onto the flat section.   mg

  An airplane pilot fell 370 m after jumping from an aircraft without hi0r8yl/fp +hy os parachute opening. He landed in a snowbank, creating a crater 1.1 m deep, but survived with only minor injuries. Assulo0yh+ ry /8pfming the pilot’s mass was 78 kg and his terminal velocity was 35m/s estimate
(a) the work done by the snow in bringing him to rest; $\approx$    J
(b) the average force exerted on him by the snow to stop him;$\approx$    N
(c) the work done on him by air resistance as he fell.$\approx$    J

A ball is attached to a horizontal cord of length L whose other end .b8sc dwc3/gd7qvtu )is fixed (Fig. 3/g d t8uqs).c wvb7cd6–43).
(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-*1d tyl axm.:r.)bo zehigh mountain. The climb is made in 5.0 h starting at an elevation of 2300ylo)tz* :b mx1dr.e.a 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 elevator is 28 m above azsh7cme -4ya3 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 Califorpea rol;)f;zq5 1uqe2n- o r1pnia claims that its lifts can move 47,000 people per hour. If the average lift carries people about 200 m (vertically) hig;ouroe; ) rn1 pelfp1aq 5-zq2her, estimate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam aq +ec1f(4j;wldqx n 1zt the rate of 650kg/s and falls vertically 81 m before strikin 1q4 ;znjxqwle(+d 1fcg 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 loopq vg2iha7i9t/utdl* qpaj 25; (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. 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 throul29i *t2 ;/ai7q va ut5qpjhdggh it.    mg

  (a) If the human body could convert a candy bar directly into work, how high cou9(5fn l16k fd-qvuhulld an 82-kg man climb a ladde (lu15hfnfdu 9v6kq l-r if he were fueled by one bar (=1000kJ)    m
(b) If the man then jumped off the ladder, what will be his speed when he reaches the bottom?    m/s

  A projectile is fired at an upwatih nus/fkp:*unqzn 8q2 ,u36 rd angle of 45.0$^{\circ} $ from the top of a 165-m cliff with a speed of 175m/s What will be its speed when it strikes the ground below? (Use conservation of energy and neglect air resistance.)    m/s

  If you stand on a bathroom scale, the spring i b6t+ + a7yv 6xlv/knrlsau+q7nside the scale compresses 0.60 mm, and it tells you your weig /av+ k+a66bnrl utsv lyxq77+ht is 710 N. Now if you jump on the scale from a height of 1.0 m, what does the scale read at its peak?    N

  A 65-kg student runs at 5m/s grabs a rope, and swings out over a lake .jlr472vp jm;t wg/d1joq0v d(Fig. 6–45). He releases the rope when jvm4w dq/;dprjjtgol702 . v1his 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 5.0 m,z)n f0ba5 l/n,,qbsve 1x odx in 9.0 s. What mv b, bdf),qnxnzo/5 es,1xal0inimum power output was used to accomplish this feat?    W

  Some electric-power companies use water to store energy. m63j o +d4ftcs lq)gq0d ff+*sWater is pumped by reversible turbine pumps from a low to a high reservoir. To store the energy produced it 6)dfm qs 0o3+ gqdljcff4*s+n 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 half9 q;gw8xam8m ywe:o1nm6uc b8. What is the spring stiffness constant for each of the two resulting spwxmq9be;6:mgm8ocyu a8n w 81rings?   k

  A 6.0-kg block is pushed 8.0 m up a rou y8e)um2s d;smgh 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, how long df qdevz+ ,u/1will it take to accelerate from 55km/h to 75km/h Assume the power stays the same, and nev /u+1dz,deq fglect frictional losses.    s

  In a common test for cardiac fu 5fr0pofm)+lb7 ik qx6nction (the “stress test”), the patient walks on an inclined treadmill (Fig. 6–46). Estimate the power required from a 75-kg patient when the treroi7bmq f06x5l) + kpfadmill 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 5x1f trufy j146 g+tyu;00-kg rock vertically upward a distance of 500 m, what was its velocity when it lug61ty1f jf u t;r4+yxeft the volcano? $\approx$    m/s
(b) If the volcano spews the equivalent of 1000 rocks of this size every minute, what is its power output? $\approx$ $a\times10^b$ W a =    b =   

  Water falls onto a water wheel from a height of 2.0 m a-c vvb0i6n7:q/gk+g( .l:c ghj szqf st a rate of 95kg/s (a) If this water wheelfgg (q-sjs6 : 7/.qkvc0+ngb vlchz:i is set up to provide electricity output, what is its maximum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s