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

1#

What is the correct unit of wr y2k,m:byu9e ork expressed 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 there is x d1*tjl-u. , mo-(e uiw7urgmno 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 b wg.()/h/sau1zh qjp rn7jie 7rick wall, the amount of work you du.)/7q nwj17sh i(a/zpe j ghro

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. mab)vxia,(ec ,;d kr(f,tqb ( How much work is bi(vrb;ka(mq)ca xd,(b,f e,t eing done in holding the 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 horizo- pejdwid*2,i r89l5h3qzcx wntally forward at a constant velocity carrying a 10-N object, the amount of ww83,pqcxwdzje- * 5 rihi d9l2ork 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.e j(9-jfxt- ra0 m then returned to its original poet -jaf(rx- 9jsition. If the total weight 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 objects7odl-mujwl wlvf x*qa4j8ae6 */) 3c do work on the object?

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. rvzdk( b*op;dig1ebhq -o j-r*p h f o59--6hu Compare the sign of the work done by gravity while the ball goes up with the 1hqfo-*p(d-k 5r*d b uhoovh; 9b-gie-zp6jr sign of the work 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 position (F vs. x) graph,ur 7 r tduc9s9v9bfp7cl s grf:k*4c83 representspu 9bdf798fgccs4r7tl3 cr ru sv :k*9

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 verijl)4v1 tiah +sus position (F vs. x), what represents the work done by the force F?hi1l )atvi4j+

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 positive, then the object's kixm kf6ce1 b+x.netic 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, theyk0hw3kw67orhw g53 p n the object'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 tu+up w+ie m:1 c42zd hxqrk)e/he 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 r3t1) fe7ugif much as a car, and is moving at twice the speed of the cagfet3r7 1i u)fr. Which statement is true about the truck's kinetic 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 h26x7-yp3(p slwd nm7edz ,b4kw ,tr0 h drxz(las half the mass of car K. The kinetic energy of car J, cox( dzh,w7lp-s el(tdr2m,dykx4 6zr3 n p07 bwmpared 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 andl +xx5yr; igzc lya ;*g0+e-tj bounces back with half of its original speed. What is the ratio of the final kinetic energy to the in;;yt ij zl*e5g+ xcl0 +-rxyagitial 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 o 2*7ned.xm uaza8 oip:f 3 m/s and a pebble is moving at a speed of 5 m/s. If both objects have the same kinetic energy, what is the ratio of the 2*up zd8 n.7me:ix aoabrick'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/ /c1axdd r5n66 /znhcps. A 1.0-kg mass is moving with speed 4.0 m/s. Both objects encounter the same constant braking forcedrcdzn66/ a xp/h1nc5, and are brought to rest. Which object travels 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 (btp ::mh 9-2nmc6ycxyq5yuu8m3p iuin a panic, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skiddedh6c2mq t8ypuuybm-xi9:mc :u3 y( 5pn , 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 orbe ;sf.3moez 6u1ulcki/dr+/m its the Sun in an elliptical orbit. Neglecting any friction effects, what h/36+/. uel1dfie;mom kr uczs appens 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 pri(dyyhnq 56i+ znciple.

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 negative potential energymjp5 kj1 d8xdb5y 98;s fgzm(z?

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. Aj(zv,db(aat;s-6 * bbkju x+ s second object with four times the mass of the first if released from the same height. The potential energy of the second objev +jbk;db*-( ( sztxa su,bja6ct 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 izg mry l8vq3,e+-oa.it to stretch 5.0 cm. If another 0.200-kg mass is addy +38zg mq.lo-,ivaered 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 energy 83pqe 2slsw*h6ggcs ) 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 tree. Compare its kinetic energy K, t2d 7m ftkjb;5u*wh(lmo its potential energ5bmwl 2uht 7(f k;jdm*y 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 3n 5dvubda9r,b+-ek zcar driving 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 object are sliding with eagzlfv)m vgc6fd; 1 7y/zq 08hqual speeds along a level frictionless surface. They both slide up the same frictionless hill. Wh damcvfhq7g zy1)/z gv8fl60;ich 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 avnm.v ;ie3 lck2(fc($m_{1}$ 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 conservasg rbd1-j.z 4ah0fyy 0tive forces0-jh y0.gr1d fys4z ab.

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 i6d+ vwho85jit olm +7ks present), to the ground below. How does the kinetic 7+j6d +thl5v8omowik energy (K) just before striking the ground compare to the 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 distan*8o7f 8muayxv5xfa2mvl : 9 xyr:fa9hce and gains 30 J of kinetic energy. Do not ignore air resistance. How much gravitational potential energy did the ball l9 x*8:rvola59xmf8vxy2:may f 7fhau ose?

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 gravik1c7nvz7 y 3uutational potential energy. Do not ignore y1u37 zunv7kc air resistance. How much 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 conservatimulcepur9fod; )8 ;.won of 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/h8 uhl4n gi6v

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 ofh(a,eyhw kn od44hd/n :w08h d 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, which is not a unit of powerlx4q u wls398b fw3z(r?

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 the time. To do so,h(4uaxh jpvd g+-. -hb -uapd+hgh xv4- .j b(hyour power output 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 acceleration,-*,flysj)c oxkyt.w 7 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 anfa0c7lh.sr lqgv p.y;)9 *uw2i gl1zzd held there. If the object weighs 90 N, how much work was done in lifting u qf 2; gl.y1vhg.z 9lrc*p7)lswzai0 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 distance pd :ox4m1,wwtof 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by the ,:wdm1xpt4w oweight 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 upward with a 7mkc /q6zucl3e 2qw3x;i 9e occonstant force of 5500 N for a distance of 50.0 m. What is the work done by th l3q x36c72co/u;iwcke 9zqmee 5500 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 const4(r z,b 1vwperant force of 5500 N for a distance of 50.0 m. What is the 4z(e1br wrpv, 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 upward with a constant fs0dlmlp*s* i1w/(k8 kg3- awrayiy 6corce of 5500 N for a distance of 50.0 m. What is the net work-r3ya d ma 6l1/p wiw0*siky*l(8cs gk 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 s ju8t4 5g:a8r +cs:hqstvcq6.0 m up 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 fruit slides 8.0 m down a ramp, inclin 1lpdu 6n2-z(.jef/anf-nb(abep5qked 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 sister5jzo zf )*qy;r Sarah in a sled on an icy surface (assume no friction), with a force of 60.)*;zqzj 5oy rf0 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 ofx99r-d2j )bjyo xj jv8 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 0 to r-yj)29o d9jj8jxvb x 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 direction of the force. The graph in Fig4+(a5 u zn;go0 jv evpppa95dr(glvu5 if;x n(. 6-1 shows the force versus the objectgl9n5g ; u pivav4jz5uepdp(o0 (v;n(rf5 xa+'s position. Find 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. The gr)g +9.v nwws4ivmy3 oraph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves fror9v wmswov+34ig y).nm 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 directio7.*,d )qtj;owr, cqy j l p.0vyw)fjcrn 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 0 to 6.)ww 0pqcqj* ;fjlv , yyo ,t.drjr7)c.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 is applied to move a 57f5ad.4hxfn( lkg8tf5-kg cart (initially at rest) across a 10 m t dl.87ff(5xnhfk 4a glevel surface. What is the final 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 roa6yoc/m g y60a;8wu applied to move a 55-kg cart (initially at rest) across a 10 m level surface. Wc6w8uyomgray0 o6/; ahat is 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 with a speed of 5.0 m/s. How much work is req9jffnpz *9t 0l-tcqm+uired to stop the9 p-ftjf* 9 cntmz0l+q 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 38-ra5a pe ew/u, re+kh uyblfeb6 o3f9)do/rat 25 m/s, what distance is required to stop a car5,obrfy9f /)ha/3ubkp dlou+ar -e e6 3e8erw moving at 50 m/s under the same condition?

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 dartq7u 9kh 4rii3ke 5a nd.ovz7,z gun propels a 10-g dart. It is cocked by exerting a force of 20 N over a distance of 5.0 cm. With what speed will thn7kz9.a e7q4, kvz iiou5d3h re 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 a8ebdc l8pj;z du 6x7g+ vertical component of 60 N. The force is applied to a b bd8;+ dzcjgx8pl67euox 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 into a bale of hay, strikiesczw8+jqx( x j8f*s3ng the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What is the average stopping force xw f8ss*x38e(zjq +jcacting 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 1 evqe+tnngp2hp a4kc,8- j1gof 7.00 m above a floor to a height of 13.0 m above the floor. What is the change in gravitv8q1ena1-h4tjpnp e+ k,gc2g ational 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 incl1lfs)k1g p* q 6at.eulined plane. The plane is 4.0 m long and rises 2.0 m. If the plane is frictionless, how much work fa*qlt) 16kgpsl1.e u 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 suh h4 cie:dg;8pring to stretch 2.0 cm. What is the spring consd4 c8he g:h;iutant?

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 constanxho4;(c zjem*yxm5 -t* fq k,st of 60 N/m. How much potential energy does it store, when stretched*-t qx5*(jyfcs;z ,omxh e4 km 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 uncompressed spring witfo0)q *kz:kkgh a spring constant of 25 N/m)g :k* f0qkzok 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 zvsj c)3vd0xs )02ij ukv )c4qconstant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretcheds4kv qc0x2z jivs0uv))j 3)c d 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.,o0a rubria ks2t./b5 qus/n constant of 15 N/m is initially compressed by 3.0 cm. How much work is .tori5a2 q/.sb s, au/k0nr burequired to compress the spring an additional 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 fromracqv pbz,a l8(.ayqdpn y(.j4 28h )n rest from the top of a 50-m high slope. What is the speed of the slier on reaching the 8arnn pv.zydlc2,h(j p(yq 4qa a).b8 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 s5jnc( 4d8 zu bjq6t0skv i8ii3peed of 4.0 m/s. Neglecting6bt3u0k( 4injzji8 8qsid v 5c friction, how fast 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 bottom, it has a sp+*w)e7rrmd4 0 omu xe mkk3r7leed of 9.80 m/s. What is the vertical height of the plae37mr k*m)wxmk 0 rud4le7r o+ne?

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 the floor, wp jh-mg0b(txa)ra 70its potential energy exactly equals its kineticmbr0- hp g)aj70( axtw 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 levelj3 r2(awea6c,bj. y+k z 5zm)i.beohb with a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanica rc2haw kz(.ae,.zye)b +i6bjmo b5j3l 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 the ground with a kinetic energy of 220 J. At ;(3; lecu5w pbxtw3rvthe highest point in its trajecw(pb r;excvwu 5;tl 33tory, its kinetic energy is 120 J. To what vertical 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 of a dip ( 4( q;fjscqxo1See 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 botf(j1csqxo 4 ;qtom 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 at a point 45 m above the)5. t n 7eusvlxuuduu8mi- k*( bottom of a dip (See Fig. 6-2). Neglect friction, what wie-x7(sun8uid 5. )mtuu k *lvull 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 they+40zqc :t7ojkiw/ is bottom 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, which is 45 m above t0s 7:ojy 4iti/zq +wckhe 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 of1q:roi+qyk;cn.yh l2 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 andgswy /1q twwxis);5pq 1lu:,i released from rest. What will be its speed at the bottom of its swixu; 1w5spq)iy:wig/,1 qt wslng?

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 spru9eia 5x .y+ z6i0wqnhing with springzxq.05ey69 hna+ wiu i 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 2000 kg car to s tn/p xzt40zn65wthy0top for a red light. What work is done by the friction force twz0 z06pthxynt4 n/5against 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 a 60.u/l 10ev-ejrkxh1i 1 rs8; nsu0-kg object and a horizontal surface is 50.0 N. If the init -vhe/11xek u8;nurs 1i0s jlrial speed of the object is 25.0 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 rbzs9ggxhz:.o*pk8jo -. i b0 bough, level surface. It has 24 J of kinetic energy. The friction force on it is a constkb : .-*zo8.hxb0 ogbzpigs9jant 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 applilb 74z:-oaffin ckisi -+,l:d ed horizontally to a 2.0-kg mass on a level surface. The coefficient of kinetic friction between the mass and the surface is 0.20loai4zd:+i7-lk,i:bn-fc sf . 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-m high slope. If the wor:jre zff7 ,9z/1lbpt ak done by tj/zz :rff7blea1 ,p9friction 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 a,+(wsrsfq ;y sg ha*(an inclined plane. The plane 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 p(sa+r,*(h; sfy agq swlane. 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 of a plane inclined at 20e abovecr 0w.ncka x51 horizontal. The coefficient of kinetic friction between the mass anc1n5c ax .0wrkd 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 strikes the gr q7-z(odyv md c6)hh1jound with a velocm6 q-)ohd(y7hj1zv c dity 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.e hul )x:qac. bf)wb+90-kg boy using energy when he runs up a flight of stairs 10.0+b9bw: q cl.)af u)xeh-m high, 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 cons,f di5 art8shker(:e;tant velocity of 5.0 m/s. What power must be delivered to the object by the forcese ;5ihe(rta8 r:,dk f?

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 10kr*1a1rnu ei .0 hr? (1 hp = n1u1e irk*ra 0746 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 of 500 W f+ax . 6dxr knz:qq, ,1bf*fnrwhile riding. How much force does her foot push with when she is traveling a:. ,z qrx6ra*nkq fnb,fx+fd1 t 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 frgkc34: 1gcc ymom 0 to 25 m/s in 7.0 s. What is the average power delivered by the engin 1g cc3:k4mycge? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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