In what ways is the word “work” as xl33 l jhe 8bd1x6x.s8*q4jdl +pi ngsused in everyday language the same as that defined+s lb3xpgnx4s1jqd 8l*d 6eilj 3 h8.x in physics? In what ways is it different? Give examples of both.

Can a centripetal forcy8 wlg.)fji :ee ever do work on an object? Explain.

Can the normal force on:d0jj 9f+b lfnu s..ba d+apv- an object ever do work? Explain.

A woman swimming upstream is not moving with respect th/; rb bnw- /dh.avyw8o the shore. Is she doing any work? If she stops swimming and mn/; ah-r bbw8h./ydwverely floats, is work done on her?

Is the work done by kinetqb193hw;b gfot f 9z4dic friction forces always negative? [Hint: Consider what happens to the dishes when you pull q3ob1thwz49fd9 fb g ;a tablecloth out from under them.]

Why is it tiring to push hard against a solid wall even though you are dohy b/ jf:p*-2wp1fp rava 0y4aing no workjprfay 0 a-v2wh4y:1pab *fp/?

You have two springs that are identical except that spring l is stifwu* b86 )p9*rcehh 9gl oxo2whfer than spring 2cwo82 e9lgp) 6hu 9r w*x*hboh $(k_1>k_2).$ 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 on ,y-7o focgqy 6a frictionless surface (Fig.6-30). The block startsfoc,yyq-6go 7 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 gravitational9yck hehe+v ( vwn o)t ym196mrki.m,( potential energy change when yn(keymt m1h.6iwc(),rv9o9 y hkm+v e ou jump as high as you can?

In Fig. 6–31, water balloons are tossed from the roof of a buildir8)es;vuv*r m ng, all with the same speed but with different launch angles. Which one has the highest speed on impact? Ignore air 8eu)m;vsvr* r resistance.

A pendulum is launched from a point that is a height h abovpk uur0j2s+tdki 6u 1fe; ;;xke its lowest point in two different ways (Fig. 6–32). During both launches, the pendulum is given an initial speed of 3.0m/s On the first launch, the initial velocity of the pendulum is directed upward along the trajectory, and on the second launch it is directed downward along the trajectory. Which launch will cause it to swing the largest angle from the d+i0tujkk 6su2;e k1rxu fp;;equilibrium position? Explain.

A coil spring of mass m rests upright on a table. Ifmpq (. j:m6(jh1ui:zov bjvh2 you compress the spring by pressing down with your hand and then release it, can the spring leave the table? Explain, using the lam(q2h16ivvjjuz mb o(hj::p. w of conservation of energy.

A bowling ball is hung from the ceiling by a steel /aw lbhjn2- h +pfi-g/u re5q8wire (Fig. 6–33). The instructor pulls the ball back and stands against the wall with the ball against his nose. To avoid injury the instructor is supposed to release the wfnpra5/8q h+j2bl h --ieu/gball without pushing it. Why?

What happens to the gravitational potential energy when water at the ,ukrj sts,s 92top of a waterfall falls to ts,ussr ,k2t9j he pool below?

Describe the energy transformations when 4lg/fu(q*f bo; 4pkej a child hops around on a pogo stick.

Describe the energy transformations that take place when a skier starts skif gf-jd137ee ning down a hill, but after a time is brought to reseg1 f-fjn de73t by striking a snowdrift.

A child on a sled (t-qj 8sgi0 j 6ch;:pxgnu,fqw5otal mass m) starts from rest at the top of a hill of height h and slides down. Does the velocity at the bottom depend on the angle of the hill if5 0igjf ,sw86nupj:qqcg-; xh (a) it is icy and there is no friction, and (b) there is friction (deep snow)?

Seasoned hikers prefer to step w6 78 :;re1e id3vmyjxlgfw j9over a fallen log in their path rather than stepping on top and jumping d;vjfg8e76 jmyiwxdw13l r9 e:own on the other side. Explain.

Two identical arrows, one.9tcm,r md .,ddumh;coe8sp4 with twice the speed of the other, are fired into a bale of hay. Assuming the hay exerts a constant frictional force on the arrows, the faster arrow willpmur,sh.,d89cd.m ode; m4ct penetrate how much farther than the slower arrow? Explain.

Analyze the motion of a simple swinging pendulum in terml6f0yb:he, 8e 2 2pmu-jhfc eos of energy, (a) ignoring friction, ,o-:0buee mehfjy6cl2h p28 f and (b) taking friction into account. Explain why a grandfather clock has to be wound up.

When a “superball” is dropped, can it rebound to a height greater than iy+h 0zkbh w+ok,wyq7 *ts original heigkb+ w7kyqwyho, z0h* +ht? Explain.

Suppose you lift a suitcase from the floor to a table. The work you do on the sut )dfd/afmdii * y/;a4itcase depends oda 4idat*ff/)m d/; yin 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 suitcase?

Repeat Question 22 for thehj3jo. -2ysae5 (f2/fxvie ot power needed rather than the work.

Why is it easier to climb a mountain via a zigzag t kt2ut ;nw/dn*rail than to climb straight utd;k2u wn*nt/ p?

Recall from Chapter 4, Example 4–14, that you can use a pulleyi0*qu,1ggsj 2r n vn9 +ggk.q velz0r, and ropes to decrease the force needed to raise a heavy0,kg vgr q +*1resg.nl0 u,9qgij2 vnz load (see Fig. 6–34). But for every meter the load is raised, how much rope must be pulled up? Account for this, using energy concepts.

  How much work is done by the gr0 wrg3lfzl: 33mcna 9bavitational force when a 265-kg pile driver falls 2.b:z3ml a3 cngfl03rw980 m?    J

  A 65.0-kg firefighter climbs a flight of staimf2r :g:c,u(cenkum-kond(- rs 20.0 m high. How much work is required?, (uc d-genmo-n:k(2fr cm uk:    J

  A 1300-N crate rests osq e,rt +yk4a5n the floor. How much work is required to move it at constant speed (a) 4.0 m along the floor against a friction force of y s5k4aet +,rq230 N,    J
(b) 4.0 m vertically?    J

  (I) How much work did the movers do (horizontally) pushing a 160-kg crate 10.3bzav z fp6wot2n;)**d m acrtz*fbz6a nowvdp *; )2oss a rough 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 across a floor at a ra) i8+z1 aqimerte of for 7.0 s. Find the net work done on the beiz)a+iq81 m rox.   J

  Eight books, each 4.38 btht;:ojv6 le+s 39 uxine8c cm thick with mass 1.7 kg, lie flat on a table. How much work is required to stack them one on top ;8cvnle8oe6j b:+t h9sit3xu of another?    J

A lever such as that shown in Fig. 6-35 can be used to liffg+6 xem)f/ho mam+m5 a objects we might not otherwise be able to lif h+a6fam mex+om) g5m/f. Show that the ratio of output force, $F_{\mathrm{O}}$, to input force, $F_{\mathrm{I}}$, is related to the lengths $\iota_\mathrm{I}$ and $\iota_\mathrm{o}$ from the pivot point by $F_{\mathrm{O}}/F_{\mathrm{I}}=l_{\mathrm{I}}/l_{\mathrm{O}}$ (ignoring friction and the mass of the lever), given that the work output equals work input.

  A 330-kg piano slides 3.6 m down a 28° incline and is kept from accelerat b7atmabhy*1w7) smh z/+d.uq.6jgjging by a man who is pushing back mj1 tq+jws 67gby.bhuamh d.)/*ag7 zon 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 l37sj z-.xw m. 0pytkthelicopter of mass M an acceleration of 0.10 g upwar. yzlk-sm wjt3x0 p7.td.    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 lp+;q1yw6 w fevinear 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, a* p9 d0u2qpatxsw 8ivsba4.o5cting along the x axis, varies as shown in Fig. 6–37. Determine the work done by this force to move the object (a) from x=qp8pu s 0xsowia 4 25.v*bt9ad0 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 c z7zpm5jm, *xin 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 molecule, with mass of 1d 1 goou2j3b/dk.xdb$5.31\times10^{-26}$typically has a KE of about$6.12\times10^{-21}$ J .How fast is the molecule moving?    m/s

  (a) If the KE of an arrow is doubled, by what factor has its speed incrk ioc1 x)/s8jig1 jka 8:w*ewqeased? $ \sqrt{a}$ a =    (b) If its speed is doubled, by what factor does its KE increase?   

  How much work is required to stopf6jyx( cb6)dk0rmn4ow+b + qt (a r3yp 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 d xk*h2 aky ocu:.b,7jaone to stop a 1250-kgcar traveling at 105km/h?$\boxed{a\times10^b\text{J}}$ a =    b =   

  An 88-g arrow is fired from a bow whose string exerts an average fo/zrboj2d-o:p rce of 110 N on the arrow over a distance of 78 cm. What is the speed of the arrow as it leaves thpdbjr -o 2oz:/e bow?    m/s

  A baseball (m=140kg) traveling 32m/s moves a fielder’s gg,f5.1bz7eeyqkk f u;love backward 25 cm when the ball is caught. What was the average force exerted by the 7ykq.b5ekf ,e1f;zu gball on the glove?    N

If the speed of a car is in.k m lho n7opwpuce7,hbq: ,.6creased by 50%, by what factor will its minimum braking distance be increas.k whp,ble7oc7 on:pqu,h6.med, assuming all else is the same? Ignore the driver’s reaction time.

  At an accident scene on a level road, investigators measure a car’s :pes*z 6a xz6oskid mark to be 88 m long. The accident occurred on a rainy day, and the coefficient of kinetic friction was estimated to be 0.42. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes. (Why does the car’s mass not matzs epa6*z:ox6ter?)    m/s

  A softball having a mass of 0.25 kg is pitched at By the time it reaches the p 07ifkm fgtd3/late, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resistance during a pitch, if the distance between the plate and the pitcher is f7 3 /mikgf0dtabout 15 m.    N

  How high will a 1.85-kg rock go if thrownrcxwt7 n +n-o5 straight up by someone who does 80.0 J of work on it? Neg rcwn-57+ tnoxlect air resistance.    m

  A 285-kg load is lifted 22.0 m vertically with an acceleration by a so8kv3c sm 42.ylv8k ,qa to6ldingle cable. De8 4 ovk8ms63qyld,al.vc t2oktermine
(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 much must thisg15du 8bhcd-iaj*a6j 0jz3 ug spring be stretched to store 25 J -5jgu* 1 abu0i6za3 j cjgd8dhof potential energy?    m

  A 7.0-kg monkey swings from one branch to another 1.2 m higher. What ir zms bt ms1gz:4i6/q,s the change in potential es:46tmz/ zsbgi,1m qrnergy?    J

  By how much does the gravitational po u38xnu;ob a:gtential energy of a 64-kg pole vaulter change:gubnxu o;3a8 if his center of mass rises about 4.0 m during the jump?    J

  A 1200-kg car rolling on a horizontal surfasx *x 33o.2g , k o*splizeucub1nif/4ce has speed v = 65 km/h when it strikes a horizontal e3f4sx*z/buou, x isgcp .3oi *kln21coiled 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 a 2.10- u-kkpp6):m)r ,ebknukg book from the ground so it is 2.20 m above the ground. What is the potential energy ofrk)me-p:,b u) pkk 6un 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 +*t- kcx o,uj/adyir6climbs to the top of a 3300-m pec ka6 ojdy-,tuxri+/*ak.
(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. The end of the sprjhky+v8br9;x 6ag( tw ing is next to the 15-cm mark on the ruler. If a 2.5-kg mass is now attachtwj 8+ab(96 gr yhxv;ked 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 ako mhhaz6sc1*ub7;pdeb +elc)5+f,ft top speed (5.3m/s) and grabs a vine hanging vertically from a t mb5ce ) od 1,be++uh6flz* f;sphkc7aall 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 rest, slides down a;.3d no0drejlue3 i.z 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 frictiolk:aj)nkv3 33zn/ys v nless 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 p ix)x10)v xx2o0cfxm transformed into gravitational potential energy with1x)0 )xim xp0 2fvxocxout the aid of a pole. With what minimum speed must Fran leave the ground in order to lift her center of mass 2.10 m and cross the bar with a speed of 0.7m/s.    m/s

  A 65-kg trampoline artu8(u, p) 9mv9um i)5zzmyjaozist jumps vertically upward from the top of a platform with a 8zmmm )z)p,u( uo99j zya5vuispeed 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 stiffe8f:lng gdl m4cg4h.0-tg* lo ness constant is 950N/m is attached to a table and is compressed down 0.150 m. (a) Wg-4 4.g g:mh8l*lng0tfld ce ohat 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 with7 opr 7)ore.ais9 7tmsout friction along the looped track shown in Fig. 6–39. If the block is to remain on the track, even at the top of the circle (whose radius is r), frm9 o7. rsoitae)pr7s 7om what minimum height h must it be released?    r

A block of mass m is attached to the end of a spring (springdfv.08 ,pl7r. bnoig ) b ai-,xikwsf, stiffness constant k)wxkad f,o.lvibi,f)7 0b 8, nr. gip-s, 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 is tied to a bungee cord whose uhfcf . :f(k-j d3wy/ulnstretched length is 12 m, and falls a total of 31 m. (a) Calculate the spfhk -cul:f w(3y .fdj/ring 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 ca3ugygwzn(0q7d is*.k r shown in Fig. 6–41 is dragged up to point 1 where it is released from rest. Assuming no friction, calculate tyuq gzk.3g(s w 0i*dn7he speed at points
2    m/s
3    m/s
4    m/s

  A 0.40-kg ball is thrown with a sp x q*a++ pyfhn*fol4k.eed of 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 placed at the bottomloj(k1+y-ie , ,r dg/e unlk79htuh- y 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 passengel-, tyr kn/j gkyoh -edei hu+l(197u,rs.

  A cyclist intends to cyehx;d )reg3by:5i2y q.pv/ltip3taby 9* a (z cle 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 a n-ix:a2,n -,s gat/n dvv0yysnd traveling 95km/h in opposite directions, collide head-on an a/xnan ,--ytn: vsy i2,vds0gd 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.+kmsn6,je qavdnn 7b 3 .b;v0u5 m high and reaches the bottom with a speed of 2.2m/s How much thermal energy due to fqs6ju0 nvdv7 b,kn.m;3 ane+briction was generated in this process?    J

  A ski starts from rest a * xfy)vtw3-w;5syd qep69ayh nd slides down a 22 $^{\circ} $ incline 75 m long.
(a) If the coefficient of friction is 0.090, what is the ski’s speed at the base of the incline? $\approx$    m/s
(b) If the snow is level at the foot of the incline and has the same coefficient of friction, how far will the ski travel along the level? Use energy methods.$\approx$    m

  A 145-g baseball is djl zvx)w) 6vh*ropped 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 bouncext5xo.nws c* 0s back to a height of 1.5 m. owx 5c.nx*0t s
(a) What fraction of its initial energy is lost during the bounce?    %
(b) What is the ball’s speed just as it leaves the ground after the bounce?    m/s
(c) Where did the energy go?

  A 110-kg crate, starting from rest, is pulled across a floor with a constsq ys se p0*6)-)-kfhehj3 copant horizontal force of 350 N. For the first 15 m the floor is frictionless, and for the next 15 m the coefficiens skjpf)-sp)c*6qh0hee -3o yt 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 If1;3m9q xhqh5kb:bm pi the average force of friction is equal to one-fifth of its weight, with what speeph9mi;mbx 3hb: qk5q1 d will it reach point 2? The distance traveled is 45.0 m. $\approx$    m/s

  A skier traveling 12m2p)d j6pr2 bx.d u gjy94pook)/s reaches the foot 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 light horizonqb-ed,bq kf(5 tal spring (k=180N/m) as shown in Fig. 6–40. It is noted that the block–spring system, when compressed 5.0 cm and releaek5fbq -d ,(qbsed, stretches out 2.3 cm beyond the equilibrium position before stopping and turning back. What is the coefficient of kinetic friction between the block and the table?   

  A 280-g wood block is firmly attached to a very light horizonta1p , z5-sylrhtsn;wy )l 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 equili1zhsyprs w)5;tl,-y nbrium position will it stretch on its first swing?    m

  Early test flights for the *sw .plme.9j;hgx wi* space shuttle used a “glider” (mass of 980 kg including pilot) that was launched horizontally at 500km/h from a height of 3500 m. The glider eventually landed at a speed of 200km/h (a)9; wm*x w.ijg.he*lsp 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 sixth-story0wh :8gd afr+b (yj4zig6b7cj window 16.0 m aboveygb0j4 6 (d j7a:ch+bwg fz8ir?    s

  If a car generates 18 hp when traveling at a steady 88km/h what mub ,esiq. jc.06gvenn. st be the average force exerted on the car due to friction and air.0jngseq bv6ncei, .. resistance?    N

  A 1400-kg sports car accelerates from rest to 95km/h in 7.+b5k p ot6yog3b+95b tvb)faw4 s. What is the average powerypvf g5bw 9bk3+ oa6btb) o+5t delivered by the engine?$\approx$    hp

  (a) Show that one British horsepo5n bp 9xp.quh* 2j9yl9rult,lwer$ \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 unitsrr;b 50l9us-g j 0s0+5asn,c qxxa.xeo0 o oxx 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 car slows down fromzpm8vni; 9rq4 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 keepzr9m 48vq;pin the car traveling at a constant 75km/h.    hp

  How much work can a 3.0-hp motor d do8u ur* gfqcjhh3gf1h0p(aff h (/0,o in 1.0 h? $a\times10^b$ J a =    b =   

  A shot-putter accelerates a 7.3-kg shot frodf9pgkd5,o sm0d79*k:ncpvbkedz9;d/ss q -m rest to 14m/s If this motion takes 1.5 s, w:kp9 /9 kd mn;zbsdfdcq*gd -,0 odsps57vke9hat average power was developed?$\approx$    W

  A pump is to lift 18.0 kg of water per minute through a heiyqjeipon z;:zwjl zg *3)u771ght of 3.60 m. What output razi jyg z7ewlquo)z3j:;n17 p *ting (watts) should the pump motor have?    W

  During a workout, the football players at State Umrpputkg4ismds(t.-t :u+6q;eo 0 j :. ran up the stadium stairs in 66 s. The stairqdsk6;tusio:pmtu j( 4p+-mge.r 0t :s are 140 m long and inclined at an angle of 32 $^{\circ} $. If a typical player has a mass of 95 kg, estimate the average power output on the way up. Ignore friction and air resistance.    W

  How fast must a cyclist clitp2u/ i.p ldb6mb 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 +2*iw 0yhc qvemaximum power output of 120 hp. How steep a hill can it climb at a con qecwyi20+h* vstant speed of 75km/h if the frictional forces add up to 650 N?    $^{\circ} $

  What minimum horsepower must a motor have561kxs g4er.em*( xd8kdsb tc to be able to drag a 310-kg box along a level floo t1 bg*xe.ss5kd(xk6emr8 cd4r at a speed of 1.2m/s if the coefficient of friction is 0.45?    hp

  A bicyclist coasts down a 7.0)v 8n/* ch:, l0ns uheb:vmtff $^{\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 havslvwz ;)z*g:. ;r 2zr6ziaazoe built “5mi/h(8km/h) bumpers” that are designed to compress and rebound elastically without any physical damage at speeds below 8km/h If the material of the bumpers permanently deforms after a compression of 1.5 cm, but remains like an elastic spring up to that point, what must the effecaowi)rl6z gz;. z*zsr v2;a :ztive 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 shelj.r x0hwv3*ej f is 10.0 cm off the ground, 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, how much work is required to fill all the shelves, assuming the books are all laying flat on the floor jh 3ew j.x0rv*to start? $\approx$    J

  A film of Jesse Owens’s famous long jump (Fig. 6–42) in the 1936 - u-b y*iju3zxmf:7-h3xl.: uzb ua hfOlympics shows that his center of mass rose 1.1 m from launch point to the top of the arc. What minimum speed did he3z3:xa.-u- b*xu:-bhf7 luzfhjmy i u 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 wi(ss z c1*se2nathout friction along the looped track shown in Fig. 6–39 is to remain on the track at all times, even at the very top of the loop of raz 2cs1nsa(*e sdius 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 withp2dqisu.6l-7gd a+:i to m;oxout his parachute opening. He landed in a snowbank, creating a craterqx6oiom ;+:dp i7.a du2-slt g 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 of length L whose other end is fn.f;o+6 p8mc 4pwelybixed (Fig. 6–pyfmbo 8n 6l;4p.c+ew43).
(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 mounreac :yytl 5+exl+a 5jx c2ie0 .x4(pwtain. The climb is made in 5.0 h starting at an elevation of . xc5e4c+ ltxaxjr 2wy+5yple(ei : 0a2300 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 elevatorj6kc1y;k5x pj 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 Californif2:,x*tl smzo5ng+by d 0x2zvj5od- wa claims that its lifts can move 47,000 people per hour. If the average lift carries people about 200 m (vertically) higher, estxmj5,v dz -z 0o*l+xfgy2w:ts onb2d 5imate the power needed.$a\times10^b$ W a =    b =   

  Water flows over a dam at the rate owi97 0ct6oz p;owo* caf 650kg/s and falls vertically 81 m before striking the turbine blades.;0oc76toaz c* i wpw9o 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 lool/a,c:bat t;;t ap4i un2dj9f p (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 frictioa,;t;2ad piltjf 4u:abt 9n/cn. 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 ;)b(ppwy hpk1bar directly into work, how high could an 82-kg man climb a laddybwh) ppk;1(p er 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 upward angle of 45rhdi kh+ ) uk9wqgh 6p,u/ci8*.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 bathro6f+*wndry 0 nlw 8wqdwn -(s5jom scale, the spring inside the scale compresses 0.60 mm, and it(8q-+6sdnfy0jwrwnl* ww n5d tells you your weight is 710 N. Now if you jump on the scale from a height of 1.0 m, what does the scale read at its peak?    N

  A 65-kg student runs at 5m/s grabs a rope, and swings out /1 t ftkn6nc0qover a lake (Fig. 6–45). He relean106qtc ftkn /ses 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 climbs a vertical dsu7(3vzyyxm 3istance of 5.0 m in 9.0 s. What 3z7 3ysuxmvy(minimum power output was used to accomplish this feat?    W

  Some electric-power companies u e **8uvk()wii)8s.nm slcm2 nadkepo .z;ei8se water to store energy. Water is pumped by reversible turbine );elzod8kias88 pmkev*u w n(2.s e)mnc*ii.pumps from a low to a high reservoir. To store the energy produced in 1.0 hour by a 120-MW ($120\times10^{6}$W) electric-power plant, how many cubic meters of water will have to be pumped from the lower to the upper reservoir? Assume the upper reservoir is 520 m above the lower and we can neglect the small change in depths within each. Water has a mass of 1000 kg for every 1$m^3$.    $m^3$

  A spring with spring stiffness constant k is cut in half.-tq8o0upnl 2 0n jlbs0 What is the spring stiffness constant for each of s-jl nu0l2 oqp80bnt 0the two resulting springs?   k

  A 6.0-kg block is pushed 8.thrupnofu k*6*yun +s ;6 .tx60 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/hdlk5 60:rpooajdu8*r to 55km/h in 3.2 s, how long will it take to accelerate from 55km/h to 75km/h Assume the power stay u6odk0:ad8rpo 5lr*js the same, and neglect frictional losses.    s

  In a common test fort c 1 6z1a; poz38(1debwm8dn ght,nhs cardiac function (the “stress test”), the patient walks on an inclined treadmill (Fig. 6–46). Estimate the power required from a 75-kg patient whea8e hw n36mz1 od,c1;1pz t(sbhdt8n gn 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-k +*txy dchz n1c9-hs(tb+vn:qg rock vertically upward a distance of 500 m, whatt1tnx: cs+ nd-9h+bqvy* (z hc was its velocity when it left the volcano? $\approx$    m/s
(b) If the volcano spews the equivalent of 1000 rocks of this size every minute, what is its power output? $\approx$ $a\times10^b$ W a =    b =   

  Water falls onto a water wheel from a height of 2.0 m at a ratq;hm8ja jl(y .e of 95kg/s (a) If this water wheel is set up to provide ejh ay;l j.q(m8lectricity output, what is its maximum power output?    W
(b) What is the speed of the water as it hits the wheel?    m/s