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

1#

What is the correct unit of work erw( em*aso34g .f:opa 0,q xoqxpressed 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 syst2/sqgq h qg+uuu -z/xg oe( b4f2i0i/jem if there 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 har4yhu2ydg1 qtx trcwy7 6r1o* bt-n3,fd against a stationary brick wall, the amount of work yot4 y1uq6f 3tbncx g2o-*th ry w,y1d7ru do

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 there. Hog(+) ybwcb kr6w much work is being done in holding theybbwg()k +rc6 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 horizontt. )wvlq7u) lmp ivh85ally forward at a constant velocity carrying a 10-N object, the amount of work .vqvt8hw) m l7p5)lui 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 lifted vertically 3 fn:y1l4yez1 g.0 m then returned to its original position. If the total weight is 30 N, how much wyy1f lze:14gnork 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 objecyfk tw xw6,au1t3l, ;tt?

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. n* nu/vj5m *pd +l:agpCompare the sign of the work done by gravity while the ball goes up with the sign of the workdu* 5na:+ vppl gmn/j* done by gravity while 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 povfz)vn hzi):e0b 22 ndsition (F vs. x) graph, representsv2evzd:nb fzi ) 20)hn

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 position (F vs. x), what represents t) b du0cq(h:v18pxvv mhe work done by the forceb 80qdxm1v(hvp:u c )v 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 positivjw/ijm7 wedr72*x.fob+ve5 e e, 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 0j9lr ul(zq4 v* ,rjxfobject'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 zero, then the object's kinetic .rgxi k (rh/* i(0msjpenergy

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 mucw;bn ivvw8 o k+cvv;5ioq, ,x2h as a car, and is moving at twice the speed of the car. Which statement is true about the truck's kinetic energy com2v;knovboqi ww ,v5 c+i8; xv,pared 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 the mass of car K. 7p 4 (altlky/v The kinetic enellk yp4(v 7t/argy of car 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 9vu9y w tjnon d8zy(m9a)6g.sand bounces back with half of its original speed. What is the ratio of the finan9v69 (yd9 )sytj nguazo.8mwl kinetic energy to the initial 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 and a pebble is moving at a speed of 5 ml:7 evz8 l,pf;cho8 em/s. If both obj7z,8 p ; eoclevhm:8flects have the same kinetic energy, 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 w0z r(9,fh v:dc hw9n.hw2hqhl ith speed 2.0 m/s. A 1.0-kg mass is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before(c lz2q,9hwhhnvfhr.9dh: 0w 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 j43ak b3wb +)5mamffr skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, unjr5 b aa3b+3m4wfk )fmder 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 orbit3- gj)oexj85bhar 8hy s the Sun in an elliptical orbit. Neglecting any friction effects, what happea hx5jj8 ybo3r g8-h)ens to the planet's kinetic energy?

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 principle.zapgpradp1 ,q2s7 w8uaby,pt1q,f6)of9 n 0e

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 systemvc/u( nme,3xerj l+zh0 6)q fz to have negative 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 hei eyfo6js xlpvy7(4 .uw*:r7qeght h above the ground. A second object with four times uj:7 r4* vw.elf67x (oeyqyps the mass of the first if released from the same height. The potential 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 streka/sj5hfbx )we, l 0g:tch 5.0 cm. If another 0.200-kg mass is added to the spring, the potential energy of the spring w5,bh fkw/l:xse 0ag j)ill 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 energy of a sy4 tssq2tlom14tdf1dmh klt (,+w; 9frstem

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 tree. Compare its kinetic energy K, to its potentikds 5cz( 3d eohro;3)c i6p1hmal energy rh koi1 3) hoe6z;d(p5c d3smcU.

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 driving up a hiltku )qoow;oa+/* , sh5rd.ff ml.

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 object are sli p ic6;ecrq)348i+wbxvz;xshding with equal speeds along a level frictionless surface. They both slide up the same frictionless hqzs6xwce;i) v3i 4;+ b8rhcpxill. 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 b+nfg lf0/*, vie-zxw$m_{1}$ 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 conservation of mechanical energy for 1rhmj p mnt 6)pgnifx:6h 4z+0conservative forcesj4)xzmf 0pi rp t61+hn :h6mgn.

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 pre j 32,yrb 2qydif 6u7g,-ggt5)jxczzxsent), to the ground below. How does the kinetic energy (K) just before striking the ground compare to tcub,-5gy 2,t)z6 g 2z3j7ygrif d qxjxhe potential energy (U) 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 gains 30 J of kinetic enerbqvo v133dz+bog+ qt4gy. Do not ignore air resistance. How much gravitational potenb +4qqz1dgt bo33ov+vtial energy 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 gravitat)xj kvupbo6 :ckj*1x k9ip47.ygq7 b gional potential energy. Do not ignore air resistance. How mux.kb 9uvbygk7picjp1j:q o*64g k )7x ch kinetic energy did 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 of energy6j rpoowe w3n69 tz95gypo5o4 .

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 isauw(mt. jn* g8

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 of power expressed in SI unitsiyuep* isqxq. b 8+f-8;r fl55+fpi qo?

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, which is not a unit of po c gb 2y,w +ggg;6agivzp*t:j6wer?

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 3 times the work in one-third aarxcb q1,d p /pmh8:te- +f2hthe time. To do so, your power output must have hq,-a dr 2b1xethcp +f8:p/ mabeen

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 acceleration, the car's engine mustoabh5frc(05 :yt4icm

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 he-f5jng5b nmk)rf 53c(0d dpvpld there. If the object weighs 90 N, how much work was done in lifting drcp)0mj( g pb5 kd v5-nf35nfit?

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 de 671ihhqg4 oaistance of 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by the weight of the book?e674 hqh 1igao

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 upward with a constant force of 5500 N for a dis 2q e.wgwnrk,h8 -l 5f-u.jt):agbebctance of 50.0 m. What is the work done by the 550auw k j:c,e)2gwb.qe8rf bh5.-tl -gn0 N force?

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 constant force of .g+xu 6dp v1p ue*/xw2s9 duec5500 N for a distance of 50.0 m. What is the work done by the w19wup 2s *e6dxv dc .upxg+/eueight 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 upward with a constant force of 5500 Ntx( muo./8r7kf n9 4 nehr8lpj for a distance of 50.0 (f.j8m e9r tpnulk4rx 87hon /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 up along az:xb bin3 (k,:nbu3to $37^{\circ}$ 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 fruit slides 8.0 m down a rampg fo ,5av icbw43yrb,:vv, qx4, 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 s i14bgjcqp **iister Sarah in a sled on an icy surface (assume no friction), with a f*qijip1c g4*borce 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 force. The graphkg0rrn*,gwqvdr+3,8 hm+re i in Fig. 6-1 shows the force versus the object's p*rrq 8dn,ri ge+0g wvh,r3+kmosition. Find the work done when the object moves from 0 to 2.0 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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52#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the 3jx4gty xm :1v pw)ty6direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find t)4 y jxv6wgmx1pty 3:the work done when the object moves from 2.0 to 4.0 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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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 force. bfv jz(o-*npl , w-n-eThe graph in Fig. 6-1 shows the force versus j,bzw -f*-( -pvnlenothe object's position. Find the work done when the object moves 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 force. The graph in Fig.m3u3jrzkup 3. a.ookd1wh3 k2 6-1 shows the force versus the object's position. Find the work done when the object moves from azodk33 prj. omk kw.21u 33uh0 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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55#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A horizontal force of 200 N isf;,w+ mu q3ari applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final kinetic energy of the car;m3,u iafwrq +t?

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 (init1nw)m7ypq f11-zpi*agh0*r1z bq t tl ially at rest) across a 10 m level surface. What is the final speed of the cart?qwpg1my*hr q- i1*t0an 17flz1) zp tb

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 movi/p -z0rv2s tcwng with a speed of 5.0 m/s. How much work is required to stop the mass2czsw/pv 0t-r ?

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 car3 srowewfm/o d*bk( --bl3 us6 initially moving at 25 m/s, what distance is required to stop a car moving at 50 m/s under the same condition?sb -6dk3lwfb*o (- somr wu3/e

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 exer7*wyur2)w0 xkzx 6 qtoting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the gun, asy qw7u2x0w xor*t)k6 zsuming 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 a vertical v-1uzvo;.ecl component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 m horizontally along the f;e 1o-ulc z.vvloor. 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 into o(f1bz5hadq: a bale of hay, striking the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm beforez:o5bqda(1 fh 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 above a floor to a hrx4:j 54cbdppuiqp(/ eight of 13.0 m above the floor. What is the change in gravitational potential en/pud5q p:brxc4 4 pij(ergy?

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 inclcbl 20,+kwr rw6(uvr4e ykppnzf- 5o*ined plane. The plane is 4.0 m long and rises 2.0 m-u +0rr4z 5eok6*2pl pnr,f(c k wvbwy. If the plane is 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, causes the sur z1adhz,)kcwg q :3v0-f4xk pring to stretch 2.0 cm. What is the spring constan q 3 a ,gkxuczk0)fh-4r1:wzdvt?

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 constant of 60 N/m. How much pot65egy ligf-4q: dmdq +ential energy does it store, wheng ym-fdq54: 6edg ilq+ stretched 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 co1 .n)mo8/p cwi mbytkaj5 o7i+1jnd*z mpress an initially uncompressed spring with a spriy i5i m z11/okb* o7.j n8+capwd)jtnmng constant 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 con:s bon32oi d5xvqf m *;b/k kk3s)gl*gstant 40 N/m from x = 0.20 m to 0.25 m? (Ass:3b2ib)ok5 v*;smqgxn* /dsgk3kl o fume the unstretched 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 constant of 15 N/m is initially compressed lv zbqwi.mwd 0(.gc- 2by 3.0 cm. How much work is required to compress the spring an additional 4.i qwd. (cg2 vml.0bz-w0 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 5sknip9ha 6sbn v0(/syu+5t 6x 0-m high slope. What is the speed of the v(xh0nuys pt+a 6i56/n9bk ssslier on reaching the bottom of 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 initial spew*nu 7z ly ;gfrs+yh30ed of 4.0 m/s. Neglecting friction, how yf+ 7;zusr *hng w3y0lfast will she be moving 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 bott3qrlhd)s 2cf*79vjg 6 5 dhlxrw3)rn zom, it has a speed of 9.809z*d h5rq)d 3s2glr3nvhr)76 jclfx w m/s. What is the vertical height of the plane?

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 m above m6g:d)q jb5/l .wi jvjthe floor, its potential energy exactly equal.5:mlb j/6q jiw)dj gvs its kinetic energy. 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 10 N, blasts straight up from ground level with a kineti+bgtyp*( , ;1cw ;pfedxwyzud 7 5q+kmc energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J. To what verticay*wcdg 1p+wmd;7, ez+(b xkuyp5q;ft l 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 the ground with a kinetic ener5 :ptdlimqt./ gy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what vertical height, relativ5i/t.tq: pm lde 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 point34- tcv; axehj1+rv mr 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coas3er v4-crx1vjht m +a;ter 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 /5zficy.cm6s1x y;mvg c*tp3at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slc ;gv zs yx.fy6tmc1m3 icp/5*ope, 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 /-d3k67 f ,eojkydtz f30 m above the bottom of a dip with a speed of 25 m/s (See Fig. 6-2). Neglect friction, what will be k/j7-f3zydfeodt 6 ,k the speed of the roller coaster at the top of the next slope, which 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 at the bottom of its swing (poi ; (yqqurn rst1zmdu0 .;y2m zod1a9h-nt

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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 riy8 wmu;)xubcn+/m7 from the vertical axis and released from rest. What will be itsi+8 um7 n/yuwbx )c;mr speed at the bottom of its swing?

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 horizontal sp 4lbovbd*15fj2cq0 on ring wi5lb j 4*2obvdf10qnc oth spring constant 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 9 n;sohxz;y-jq k+3 gr2000 kg car to stop for a red light. What work is done by the 9h gs+3ykxz-j;n ro;q friction force against the wheels?

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 between+3dq:m ;qr uff a 60.0-kg object and a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, what distance will it slide before coming to a stop?;qf +uqrf:d 3m

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 oqi(cuep-f33 l6 ezu9v f kinetic enerlpfeei33z( c- u6 uvq9gy. The friction force on it is a constant 0.50 N. How far 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 applied hhzq *,s:k3qw:lfv6u iorizontally to a 2.0-kg mass on a level surface. The coefficient of kinetic fricti zkhs 3v:quif6:w,*l qon between 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 :c+)h uoekfl; from the top of a 50-m high slope. If the work do )o:ecluh +;fkne by 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. )m bu7yzn7xr)v/ 6uhz m wdd)5 The plane is 4.0 m long and rises 2.0 m. It requires 3200 J ouzhwm z 6x77u) vyrdnm )/bd5)f work to get the box to the top of the plane. What was the magnitude of the average friction force on the box?

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 at the top 9 c( ou,6n yvs9g:mktxof a plane inclined at 20e above horizont9n,(u kts9:vog6 xycm al. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speed of the mass 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 10.0 m, and strik5r8 8awts( r a0hrsl9a u84tnoes the ground with a velocit ns8osr8a 8uaarth (49l w0rt5y of 7.00 m/s. What average force 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 energy when he runs up a flight of mh9vmgoobx. .i2hs; xq;w+- b stairs 10.0-m hmqb;sb ; + hv.2-o9wmo xhxg.iigh, 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 a constant velocity of 5.0 m/s5 bqnrxnjg7( .. What power must be delivered to the object by th bn(.jgx75nr qe 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.n .gc yh+wqht418l1ks0 hp motor that runs for 1.0 hr? (1 hp =nlhkc+q y8gh.4 1s1w t 746 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 the rate o9 8)mqkht;tp,fwj :vge3)o ftf 500 W while riding. How much force does her foot push withq ;j)9kvpw3 mttt8fge) h ,:of when she is traveling 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 ,gw6kn3xe8 t zd2ogc8m/s in 7.0 s. What is the average power delivered by the engn,g688kxwed 3z2cgto ine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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