Physics Unit6: Work and Energy - 51fly国际课程 (51fly.win)

1#

What is the correct unit of work expressebes m+: 1qd *ki1.mt*jiniv 4pd in SI units?

A. $kg m/s^2$

B. $kg m^{2}/s$

C. $kg m^{2}/s^2$

D. $kg^2 m/s^2$

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2#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Can work be done on a system if therepn b;.xxf(n7 w is no motion?

A. Yes, if an outside force is provided.

B. Yes, since motion is only relative.

C. No, since a system which is not moving has no energy.

D. No, because of the way work is defined.

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3#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If you push twice as hard against a stationary brick wall, the amount of worwca 7 h 0iold*-hs4/slk you dol/ l*sh7osdwi0 h- ac4

A. doubles.

B. is cut in half.

C. remains constant but non-zero.

D. remains constant at zero.

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4#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 50-N object was lifted 2.0 m vertically and is being held tqqdhpb 3md poq x/k(u5335q 8khere. How much work is being done in holding thp8 5 qdpkqd/ u 3o53qxmb(h3qke box in this position?

A. more than 100 J

B. 100 J

C. less than 100 J, but more than 0 J

D. 0 J

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5#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If you walk 5.0 m hor c6u s9v+nb8fl e02mgdizontally forward at a constant velocity carrying a 10-N object, the amount bmu 9ln 2svf806gd+ce of work you do is

A. more than 50 J.

B. equal to 50 J.

C. less than 50 J, but more than 0 J.

D. zero.

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6#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A container of water is la8 fyv66cc4jtkgd ,-o ifted vertically 3.0 m then returned to its original position. If the total wedc4 fotky6-g,8 v6 cjaight is 30 N, how much work was done?

A. $45 \; J$

B. $90 \; J$

C. $180 \; J$

D. No work was done.

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7#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Does the centripetal force acting on an object do work on the l0qa54vrgc :5+bj ozqobject?

A. Yes, since a force acts and the object moves, and work is force times distance.

B. Yes, since it takes energy to turn an object.

C. No, because the object has constant speed.

D. No, because the force and the displacement of the object are perpendicular.

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8#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You throw a ball straight up.50u9z za8eo/p 3gapza Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity whuo5gpa a8za9z0 ze/p 3ile it goes down.

A. Work is + on the way up and + on the way down.

B. Work is + on the way up and - on the way down.

C. Work is - on the way up and + on the way down.

D. Work is - on the way up and - on the way down.

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9#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The area under the curve, on a Force versus positiolo1motpk,ob+t t02 ae j 83m1an (F vs. x) graph, representsompe1tm238 ,ot0 lk+to1b aaj

A. work.

B. kinetic energy.

C. power.

D. potential energy.

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10#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

On a plot of Force versus positiong xwq rblx0ll:td2img ;h/- 7+ (F vs. x), what represents the work done by the fowim-gb :lgqlrldx ; 0x+t /h27rce F?

A. the slope of the curve

B. the length of the curve

C. the area under the curve

D. the product of the maximum force times the maximum x

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11#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity $\frac{1}{2} \; mv^2$ is

A. the kinetic energy of the object.

B. the potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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12#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an object is w)uxxm)lx7 f zv)o8b/ positive, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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13#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an object is negative, then the objvroz5)kh(y x/u4kc uyhy7 58+y +thppect's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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14#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an object is zer/h0ob,: apwtpo, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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15#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A truck weighs twice as much as a cep2x 7o tptw mj,;kbe: 2ti/w*ar, and is moving at twice the speed of the car. Which statement is true about the truck's kine,wkbxpe:*/p2 tt m2tie7;w jo tic energy compared to that of the car?

A. All that can be said is that the truck has more kinetic energy.

B. The truck has twice the kinetic energy of the car.

C. The truck has 4 times the kinetic energy of the car.

D. The truck has 8 times the kinetic energy of the car.

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16#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Car J moves twice as fast as car K, and car J has half. bwbfz2m +vb2 the mass of car K. The kinetic energy of carm2+fbzw2b v. b J, compared to car K is

A. the same.

B. 2 to 1.

C. 4 to 1.

D. 1 to 2.

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17#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object hits a wall and bounces back with half of its original spe,1j llies/i d;g -opy*a6f)pqed. What is the ratio of the final kinetic energy to the initi-iq/* p flyae;pg,)6si1j ld oal kinetic energy?

A. \frac{1}{2} \;

B. 1/4

C. 2

D. 4

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18#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A brick is moving at a speed of 3 m/s annd(vi txcw/un ; d/,+ad a pebble is moving at a speed of 5 m/s. If both objects have the same kinetic energy, c;wt(d /+v inx/dnua,what is the ratio of the brick's mass to the rock's mass?

A. 25 to 9

B. 5 to 3

C. 12.5 to 4.5

D. 3 to 5

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19#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 4.0-kg mass is moving with speed 2.0 m/s. A 1.0-kg may(y,*h2t dmlvss is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels y2,hyl* mv(dt the greater distance before stopping?

A. the 4.0-kg mass

B. the 1.0-kg mass

C. Both travel the same distance.

D. cannot be determined from the information given

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20#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You slam on the brakes of your car in a panic, and skid a certain dista 8 etujhrqx0jd+h6/(mnce on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, 0 j/6 dqrhhumjt+ e8x(under the same conditions?

A. It would have skidded 4 times farther.

B. It would have skidded twice as far.

C. It would have skidded 1.4 times farther.

D. It is impossible to tell from the information given.

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21#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A planet of constant mass orbitlwn-r+vxp l :);ivr+5tw nc9e s the Sun in an elliptical orbit. Neglecting any friction effects, what happens to the planet's kinetic ene n+ -:9vr)iv tlxwcwre+n 5l;prgy?

A. It remains constant.

B. It increases continually.

C. It decreases continually.

D. It increases when the planet approaches the Sun, and decreases when it moves farther away.

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22#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the work-energy priw-- rw+qy2q bb 5kvn7uj78hhgnciple.

该题自我估分: (必填) (满分:1.0分)

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23#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity mgy is

A. the kinetic energy of the object.

B. the gravitational potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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24#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity $\frac{1}{2} \; kx^2$ is

A. the kinetic energy of the object.

B. the elastic potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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25#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Is it possible for a system to have negao/vu ,9dgz6 ty4 wyvf;pnwq0.tive potential energy?

A. Yes, as long as the total energy is positive.

B. Yes, since the choice of the zero of potential energy is arbitrary.

C. No, because the kinetic energy of a system must equal its potential energy.

D. No, because this would have no physical meaning.

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26#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object is released from rest a height h above the ground. wtie)k1j7vo b-2et 4 i/p:cp fA second object with four times the mass of the first if released from the same height. The potp1jwe 47tpfcvi2:ki/)b t- eoential energy of the second object compared to the first is

A. one-fourth as much.

B. one-half as much.

C. twice as much.

D. four times as much.

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27#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.200-kg mass attached to the end of a spring causes it to/in zb,r7kwj dwi:zl 0d7 )+;f)r aprh stretch 5.0 cm. If another 0.200-kg mass iszjb, wz)7kr;i /r:f0+ 7rdhal idpw )n added to the spring, the potential energy of the spring will be

A. the same.

B. twice as much.

C. 3 times as much.

D. 4 times as much.

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28#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The total mechanical enereb- m56t fdzt6gy of a system

A. is equally divided between kinetic energy and potential energy.

B. is either all kinetic energy or all potential energy, at any one instant.

C. can never be negative.

D. is constant, only if conservative forces act.

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29#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An acorn falls from a trerp xm-i2snvt c/9w6i.qhy3z ,e. Compare its kinetic energy K, to its potential eneripnc3w m .th6-vi9 r/qs xz,2ygy U.

A. K increases and U decreases.

B. K decreases and U decreases.

C. K increases and U increases.

D. K decreases and U increases.

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30#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Describe the energy of a car drivi ,/r* bge e8 a/taqnnyg9g,t6gng up a hill.

A. entirely kinetic

B. entirely potential

C. both kinetic and potential

D. gravitational

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31#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A lightweight object and a very heavy ob86wzd, okt; tw, atee5/y(ejqject are sliding with equal speeds along a level frictionless surface. They both slide up the same a,o;t(/kjte6 wyz5w8t dee , qfrictionless hill. Which rises to a greater height?

A. The heavy object, because it has greater kinetic energy.

B. The lightweight object, because it weighs less.

C. They both slide to the same height.

D. cannot be determined from the information given

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32#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Consider two masses oshl*sl5h hrd5fk)50h d.t;r $m_{1}$ and $m_{2}$ at the top of two frictionless inclined planes. Both masses start from rest at the same height. However, the plane on which $m_{1}$ sits is at an angle of $30^{\circ}$ with the horizontal, while the plane on which $m_{2}$ sits is at $60^{\circ}$. If the masses are released, which is going faster at the bottom of its plane?

A. $m_{1}$

B. $m_{2}$

C. They both are going the same speed.

D. cannot be determined without knowing the masses

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33#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the principle of conservachok ,g9leu *8tion of mechanical energy for conservative forces.* l e9u8kcho,g

该题自我估分: (必填) (满分:1.0分)

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34#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball falls from the top of a building, through the air (air friction is preseoedk19)nme 1m nt), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (Ue)11m9de n omk) at the top of the building?

A. K is equal to U.

B. K is greater than U.

C. K is less than U.

D. It is impossible to tell.

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35#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and g z qlk-.sksiw)j/(k u5ains 30 J of kinetic energy. Do not ignore air resistance. How much gravitational potential enerq(jz-ssiuk wkl/. k)5gy did the ball lose?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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36#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and loses 30 J of(w:k2 aeqrpyf q 6+e6e gravitational potential energy. Do not ignore air resistance. How much kinetic energy p+6(q: qreek2wy e6fadid the ball gain?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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37#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the law of conservation ohgp6:6 0 nxemgf energy.

该题自我估分: (必填) (满分:1.0分)

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38#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity Fd/t is wni r) x*nsawh;(fi5 l.1r3pk

A. the kinetic energy of the object.

B. the potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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39#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What is the correct unit qylkmi 6n.ko0 q qa5*(of power expressed in SI units?

A. $kg m/s^2$

B. $kg m^{2}/s^2$

C. $kg m^{2}/s^3$

D. $kg^2 m/s^2$

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40#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Of the following, which3lcqth+q6: 7bl.uu x r is not a unit of power?

A. watt/second

B. newton-meter/second

C. joule/second

D. watt

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41#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Compared to yesterday, you did 3ns1gx c p59or.zmul*2 times the work in one-third the time. To do so, your power org2us*cn1ol z5.px9 mutput must have been

A. the same as yesterday's power output.

B. one-third of yesterday's power output.

C. 3 times yesterday's power output.

D. 9 times yesterday's power output.

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42#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

To accelerate your car at a constant acceleratio-rxr5 iw lud , -59hppg5;eqfhn, the car's engine must

A. maintain a constant power output.

B. develop ever-decreasing power.

C. develop ever-increasing power.

D. maintain a constant turning speed.

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43#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object is lifted vertically 2.0 m and held there. If the obje .ekv5qkmq qf9gi)1 g1l8h ,ijct weighs 90 N, how much work was doni l 9,.iqemg vfh)gk1q58k1jq e in lifting it?

A. $360 \; J$

B. $180 \; J$

C. $90 \; J$

D. $0 \; J$

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44#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You lift a 10-N physics book up in the air a d5 frmcn;.dph/ istance of 1.0 m, at a constant velpnfh/ c5;.mrdocity of 0.50 m/s. What is the work done by the weight of the book?

A. +10 J

B. -10 J

C. +5.0 J

D. -5.0 J

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45#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upwarkt) s87a ufep4vok2 3cd with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the 5500 N forcepsf82 ev37a ckoutk)4 ?

A. $2.75 \times 10^{5} \; J$

B. $-2.45 \times 10^{5} \; J$

C. $3.00 \times 10^{4} \; J$

D. $-5.20 \times 10^{5} \; J$

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46#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward with a uns*ti,-ivu.s3 4 j5,i, f gngiunp7g constant force of 5500 N for a distance of 50.0 m.,-tj*pnfsni u.43i g 5,ui vsggu7n, i What is the work done by the weight of the elevator?

A. $2.75 \times 10^{5} \; J$

B. $-2.45 \times 10^{5} \; J$

C. $3.00 \times 10^{4} \; J$

D. $-5.20 \times 10^{5} \; J$

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47#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upw) w )gm zk6av-o5i(gouard with a constant force of 5500 N for a distance of 50.gk))u6 oi a(mgz 5-vow0 m. What is the net work done on the elevator?

A. $2.75 \times 10^{5} \; J$

B. $-2.45 \times 10^{5} \; J$

C. $3.00 \times 10^{4} \; J$

D. $-5.20 \times 10^{5} \; J$

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48#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30-N box is pulled 6.0 m 8an m4g:oduyc l uc9*0up along a $37^{\circ}$ inclined plane. What is the work done by the weight (gravitational force) of the box?

A. $-11 \; J$

B. $-1.1 \times 10^{2} \; J$

C. $-1.4 \times 10^{2} \; J$

D. $-1.8 \times 10^{2} \; J$

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49#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 4.00-kg box of fruit409a( (jdlnatqvnpu(+q; t pl slides 8.0 m down a ramp, inclined at $30^{\circ}$ from the horizontal. If the box slides at a constant velocity of 5.00 m/s, what is the work done by the weight of the box?

A. $157 \; J$

B. $-157 \; J + 78.4 \; J$

C. $78.4 \; J$

D. $-78.4 \; J$

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50#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Matthew pulls his little sister Srp(ueuuo,f( 8(;2up j;frue edw 2 a8barah in a sled on an icy surface (assume no friction), ,8(;( d urupu2r uufb j;2w8epoe(f eawith a force of 60.0 N at an angle of $37^{\circ}$ upward from the horizontal. If he pulls her a distance of 12.0 m, what is the work done by Matthew?

A. $185 \; J$

B. $433 \; J$

C. $575 \; J$

D. $720 \; J$

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51#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the forceo- -rckz)dht*ihba6,i l6 yx: . The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 0 to 2.0 m.xborh6 -cyalt*iz :h,-k)i d6

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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52#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in tnluh7 ,c8.cp yhe direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 2.0 to 4.0ch.cp,ul 87ny m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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53#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the for uw:jdd:i5xq1ce. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moji:d5 udw:1qxves from 4.0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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54#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the formzx+y)xnoxr)rsn +hmx c5 t*.0 4rrh4ce. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 0 to 6.0 )mtn4z rn hc.0 *+symoxxxr4+rrx h)5m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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55#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A horizontal force of 200 N is applied tstn8ndp(; k3k o move a 55-kg cart (initially at rest) across a 10 m level surface. What is the fndpk 38(n;sktinal kinetic energy of the cart?

A. $1.0 \times 10^{3} \; J$

B. $2.0 \times 10^{3} \; J$

C. $2.7 \times 10^{3} \; J$

D. $4.0 \times 10^{3} \; J$

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56#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A horizontal force of 200 N is applied to move a 55-kg cart (initiallrx ) z*3fioev( - ifb3co)jn+hy at rest) across a 10 m level surface. What is+(r3bi*zjvf c-h3) )xn ofi oe the final speed of the cart?

A. 73 m/s

B. 36 m/s

C. 8.5 m/s

D. 6.0 m/s

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57#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-kg mass is moving 7rec,fy10tn:j8:y b k fa(uvjwith a speed of 5.0 m/s. How much work is required to stop theny7b,vrejfk1 tafcj:8y: (u0 mass?

A. $50 \; J$

B. $75 \; J$

C. $100 \; J$

D. $125 \; J$

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58#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If it takes 50 m to stop a car initially moving at 25 m/s, what distan 0dlk,z1ybx .lce is required to stop a car moving at 50 m/s under the same 0lxd 1z l.ky,bcondition?

A. $50 \; m$

B. $100 \; m$

C. $200 \; m$

D. $400 \; m$

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59#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring-driven dart gun propels a 10-g dart. It is cocked by exertqrt1hmkmm 8w8p u 1x1*ing a force of 20 N over a distance of 5.0 cm. Witr k 1mmt8811p *whmuxqh what speed will the dart leave the gun, assuming the spring has negligible mass?

A. 10 m/s

B. 14 m/s

C. 17 m/s

D. 20 m/s

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60#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 100-N force has a horizontal component of 80 N and 2:zidsv9y. w pa vertical component of 60 N. The force isy2vs:d w i.pz9 applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 m horizontally along the floor. What is the cart's final kinetic energy?

A. $200 \; J$

B. $160 \; J$

C. $120 \; J$

D. zero

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61#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An arrow of mass 20 g is shot horizontally igj(ya9 (w jz 5lpak9r.nto a bale of hay, striking the hay with a velocity of 60 m/s. It pezprw .ka9j 5a(yjg(9 lnetrates a depth of 20 cm before stopping. What is the average stopping force acting on the arrow?

A. $45 \; N$

B. $90 \; N$

C. $180 \; N$

D. $360 \; N$

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62#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 15.0-kg object is moved from a height of 7.00 m abojl-epjs (:7 n r*ui,mjve a floor to a height of 13.0 m above the floor. What is the chi7(,jr- *lujejs: mnpange in gravitational potential energy?

A. zero

B. 1030 J

C. 1176 J

D. 1910 J

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63#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 400-N box is pushed up an inclined plane. The plane is 4.0 m long ahcoc3 -oyd*t 1:ps )*-fjvm rpnd rises 2.0 m. If the plane i3 m:ht)1 -rodpsc** ojv pc-fys frictionless, how much work was done by the push?

A. $1600 \; J$

B. $800 \; J$

C. $400 \; J$

D. $100 \; J$

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64#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-kg mass, hung onto a spring, causesjm2w l4,xh+)/od thazenv0,o the spring to stretch 2.0 cm. What is the spring cons o, jm/zvant)wh 0,+oled4xh2tant?

A. $4.9 \times 10^{3} \; N/m$

B. $5.0 \times 10^{3} \; N/m$

C. 20 N/m

D. 2.0 N/m

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65#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring is characterized by a spring hnboy;ur2j xgk,r5 13 constant of 60 N/m. How much potential energy does it store, when stretched1;uorn 352hkgbx,j ry by 1.0 cm?

A. $3.0 \times 10^{-3} \; J$

B. $0.30 \; J$

C. $60 \; J$

D. $600 \; J$

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66#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Calculate the work required to compress an initially uncomuvkczvg . qu *a)me45 ,sboq3,pressed spring with a spring conss*uk3uv obgc.e 5az ,) ,mqvq4tant of 25 N/m by 10 cm.

A. $0.10 \; J$

B. $0.13 \; J$

C. $0.17 \; J$

D. $0.25 \; J$

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67#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What work is required to stretch a spring of spring cr r-i7f pim675sjlsn2f4(gr qtigs3 )onstant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretch652gfnip)4il ft7r7gms 3risj s(qr- ed position is at x = 0.)

A. $0.45 \; J$

B. $0.80 \; J$

C. $1.3 \; J$

D. $0.050 \; J$

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68#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring with a spring)bc s/dnsbl l;(:ka f- constant of 15 N/m is initially compressed by 3.0 cm. How much work is required to compress the spring an as:/fkn(s ;lbb dc -)ladditional 4.0 cm?

A. $0.0068 \; J$

B. $0.012 \; J$

C. $0.024 \; J$

D. $0.030 \; J$

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69#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 60-kg skier starts from rest from the top of a 50-m high slope. What is v3ph dg.bi 5k9 e45ze8p by lvhegs*1/c1wbn6the speed of the slier on reaching the bottom okpd1b vg.6en 5ee wcg54 v9ylbh*/bspi 1z8 3hf the slope? (Neglect friction.)

A. 22 m/s

B. 31 m/s

C. 9.8 m/s

D. 41 m/s

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70#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A skier, of mass 40 kg, pushes off the top of a hill with an iniql/r7)( ad wop5q/vcnsm )s:ytial speed of 4.0 m/s. Neglecting friction, how fast will she be moving5 o/)q)qsc (:var/l p7dsmnwy after dropping 10 m in elevation?

A. 7.3 m/s

B. 15 m/s

C. 49 m/s

D. 196 m/s

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71#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object slides down a frictionless inclined plane. At the bottom, it has a3crr1 y9m ha1e speed of 9.80 m/s. What is the vertical height of the planm1rh9e a1cr3y e?

A. $19.6 \; m$

B. $9.80 \; m$

C. $4.90 \; m$

D. $2.45 \; m$

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72#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1.0-kg ball falls to the floor. When it is 0.70)j6l3 rw9 l h5b1cuesi m above the floor, its potential energy exactly equals its kinetic enerl 1) swi5bhurj9e cl36gy. How fast is it moving?

A. 3.7 m/s

B. 6.9 m/s

C. 14 m/s

D. 45 m/s

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73#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A toy rocket, weighing k k.x9yp62ttg-fng;f10 N, blasts straight up from ground level with a kinetic energy of 40 J. At the exact top of its trajectorp gnk gtf; .-ykx629fty, its total mechanical energy is 140 J. To what vertical height does it rise?

A. $1.0 \; m$

B. $10 \; m$

C. $14 \; m$

D. $24 \; m$

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74#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A projectile of mass m leaves th,x ic i q7).dinr :9.thvx/wdwe ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what vedwnx .w i.ii7hxd:ctq) 9v/r ,rtical height, relative to its launch point, did it rise?

A. $\frac{220}{mg} \; m$

B. $\frac{120}{mg} \; m$

C. $\frac{100}{mg} \; m$

D. Impossible to determine without knowing the angle of launch

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75#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts from rest at a point 45 m above the bottom e1pnybuctl52 mm *h:,of a dip (See Fiuh 2b*t 5 n,1lycem:mpg. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 17 m/s

C. 24 m/s

D. 30 m/s

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76#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts with a speed of 5.0 m/s/xfm7 :vx(pop*p6 g 9 jub2ppo at a point 45 m above the bottom of a dip (See jp( u7pv9pmx/xofpbp:*go 26 Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m above the bottom of the dip?

本题所包含的其它图片:

A. 12 m/s

B. 14 m/s

C. 16 m/s

D. 18 m/s

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77#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts at a point 30 m above the botto* ;9)kxri;iagoukc ;f,zs6ym +i8karm of a dip with a speed of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, w mskay6f;*oxrriu;ia8; k+9,gc ki z)hich is 45 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 16 m/s

C. 18 m/s

D. 20 m/s

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78#

( 1.0 分) 切至整卷模式搜藏此题

What is the minimum speed of the ball atsmkvft: x:u-24ql *z i the bottom of its swing (point

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79#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A:2.2 m/s

A. 3.1 m/s

B. 4.4 m/s

C. 4.9 m/s

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80#

( 1.0 分) 切至整卷模式搜藏此题

难度:2

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81#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A pendulum of length 50 cm is pulled 30 cm away from the vertical axis and rez 9k i;+s/ub j:eoorb8leased from rest. What will be its speed at the bottom of its swinerj:zb9 8 soiuk+;o/bg?

A. 0.50 m/s

B. 0.79 m/s

C. 1.2 m/s

D. 1.4 m/s

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82#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontafy, u*1t4tn qp:o lz(gl spring with spring coygf:4 pulz(1tn* t,qonstant of $2.0 \times 10^6 \; N/m$. What is the maximum compression of the spring? (Neglect the mass of the spring.)

A. $0.17 \; m$

B. $0.34 \; m$

C. $0.51 \; m$

D. $0.68 \; m$

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83#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A driver, traveling at 22 m/s, slows down her 2000 kg car to stop for a red lfqev;r /q /ci92 lvla+ight. What work is done by the friction force against the w ;qv9f2+qre/laicvl /heels?

A. $-2.2 \times 10^{4} \; J$

B. $-4.4 \times 10^{4} \; J$

C. $-4.84 \times 10^{5} \; J$

D. $-9.68 \times 10^{5} \; J$

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84#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The kinetic friction force betweenc7 k.(nswkc f ba.zr+- a 60.0-kg object and a horizontal surface is 50.0 N. If the initial speed of the object is 25cn.(+kakc.s-wz fbr7.0 m/s, what distance will it slide before coming to a stop?

A. $15.0 \; m$

B. $30.0 \; m$

C. $375 \; m$

D. $750 \; m$

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85#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 12-kg object is moving on a rough, level surface. It has 24 J of kim x xuf 67fwsfsz2j-5om2 8i4t-y:k sinetic energy. The friction force on it is a constant 0.50 N. How far iofm :--t2sx4fum x6fyw sj z857iks2 will it slide?

A. $2.0 \; m$

B. $12 \; m$

C. $24 \; m$

D. $48 \; m$

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86#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force of 10 N is applie1*99iwxidg rid horizontally to a 2.0-kg mass on a level surface. The coefficient of kinetic friction bx1rgi*wi d99i etween the mass and the surface is 0.20. If the mass is moved a distance of 10 m, what is the change in its kinetic energy?

A. $20 \; J$

B. $39 \; J$

C. $46 \; J$

D. $61 \; J$

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87#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 60-kg skier starts from rest from the top of a 50:q7.pdbuu l qhs/* o7n-m high slope. If the work done byup7q lhd/qns7o.b: u* friction is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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88#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An 800-N box is pushed up an inclined plane. The pla( y,t f;x (m eaeaxc,vw29erwdvu75+xne is 4.0 m long and rises 2.0 m. It requires 3200 J of work to get the box to the top of the plane. What was the magnitude of the average friction force on the boxx+;2 v 5mavdwrf t,ee7 ux(9aycwe,x( ?

A. $0 \; N$

B. non-zero, but less than 400 N

C. $400 \; N$

D. greater than 400 N

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89#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 2.0-kg mass is released from rest a0agn*ya0 tfcxx5f5g* t the top of a plane inclined at 20e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speed of the mnfg*0xfygx0a 5a 5 *ctass after sliding 4.0 m along the plane?

A. 2.2 m/s

B. 3.0 m/s

C. 3.5 m/s

D. 5.2 m/s

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90#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30.0-N stone is dropped from a height of 10.0qzicu q45.arbc8o: -aka 1/uz m, and strikes the ground with a velocity of 7.00 m/s. What average a a:a.rbu5ic ocz-/zk qq 814uforce of air friction acts on it as it falls?

A. $22.5 \; N$

B. $75.0 \; N$

C. $225 \; N$

D. $293 \; N$

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91#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

At what rate is a 60.0-kg boy using vm+fv) qr/vy: energy when he runs up a flight of stairs 10.0-m high,ryq/v+m)v :v f in
8.00 s?

A. $75.0 \; W$

B. $735 \; W$

C. $4.80 \; kW$

D. $48 \; W$

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92#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-N force is needed to move an object with atkfpeo( h4 --f09et l.e fs/pf constant velocity of 5.0 m/s. What power must be delivered to the ob/ l h f.ee4ptos09 p-tkf(ffe-ject by the force?

A. $0.50 \; W$

B. $1.0 \; W$

C. $50 \; W$

D. $100 \; W$

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93#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

How many joules of energy are used by a 1.0 hp motor that runs for 1.0 hr? (1 ;-4-j9 vqkuajhdb 0brhp = 7b 4a;jv-b- khqj d9ur046 W)

A. $3.6 \times 10^{3} \; J$

B. $2.7 \times 10^{6} \; J$

C. $4.5 \times 10^{4} \; J$

D. $4.8 \; J$

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94#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A cyclist does work at thhex d+1l pba:,wun7: be rate of 500 W while riding. How much force does her foot push with when she is travelie,:bhd l bn uxpa+:w17ng at 8.0 m/s?

A. $31 \; N$

B. $63 \; N$

C. $80 \; N$

D. $4000 \; N$

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95#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s. What is the averag-luynymjiv; . vp3- (je power delivered by the engine? (1 3nvympyj-lu(v- j .;ihp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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