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

1#

What is the correct unit of work expressed in SIe(f 37y tignm; 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 no motisn 6z9zknv s qn:.,zkfz*9 9mkon?

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 amounf ;yy cqdcqju4f+.-g7t of work you doygyudq- c.;fc7+ q4fj

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. How much wormy/vn5/7n3s+ ucqcvkhgrfq y uz2 9:0 k is being done in holdingvkfq9 q+m0 uc7chn:zvu2 3gysn/y/r5 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 horizontally forward at a constant velocity carryinwwk2ee*phk w8g.6gvz /ua.9og a 10-N object, the zgkw 962*wo.epvg .a 8hek w/uamount 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 lifted vertically 3.0 m then returned to its original po(on ,i s0ec6,p,wwpfk6zap 4(* ea qqmzke /5xsition. If the total weigps,c(w6emp0ke4,pqz *f z6k e/ 5o qax ,wian(ht 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 centripetalo4r r*jrhb1i. force acting on an object 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. Compare the sign of the workj;d vx (wr:gx jbj8/z0/rx7 zk done by gravity while the ball goes up with the jrxz gx 0jr( dk;/v7:8z/ xbjwsign 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 (Fje0cpx0 y*:iu6c ci 8oxd- 9fj vs. x) graph, representsxi cj60fo8 p 0:uy* c9dj-iecx

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 the workask z-r* :m dxch1(z 5:)dkcah done by the force Fhrcdkczdh1x :( z-s*:)am5 ak?

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, to p0,wz:3zp. ) 3np.ku*j.e:cwo6smomvmtq rhen 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, txho- tk8aqg-;e4 tx ,yhen 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 f nn4 p.z4g:;ax b6gbp8b7n uda/ocz3an object is zero, 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 y 8o3u lihswew7bb8:89t rc7c car, and is moving at twice the speed of the car. Which statement is true about the truck's kin3io 8cbw7ye7b hu s89wlct :8retic 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 s if5n *12gda(v dke4cK, and car J has half the mass of car K. The kine (4 2 1nde5g*vacskdiftic energy 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 and bounces back wi egz2g ;x4em (gxfuq3in0xil-.x,g.c th half of its original speed. What is the ratio of th;x.qmn xc3(.04iezggfex-x g,li u g2e final 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 movi6x t6 +odabtp* n 6io/.yb)fgrng at a speed of 5 m/s. If both objects have the same kinetic energy, what is the ratio of the brick's mass to the rbfgri/dy)6otn to+ .p*6 ab 6xock'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 witx3x+ u frjv1/)y6ovo dh 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 stoppin6y+u1odxrfvj)xv 3 o/g?

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, any57vbp90dpsds 68ifkyt6y 9 md skid a certain distance on a straight, level road. If you had been travelyybpv 8syfd6mdp7k 9ti90s6 5 ing twice as fast, what distance would the car have skidded, 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 orbits the Sun in an elliptical orbit. Neglecti0sg ivl*gq 87 bx0wd,8b5 rsfpng any friction effects, what happens to the planet's kineti5pw8bg 0,r *sfd lqxbgsv i087c 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 princc80 ku 8gq+ n0b1ek7ltsxtwm:iple.

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 potenticd n:l7opo(5,9p0k.iis dhplal 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 heightchj-r2 pj(m (car*uj, h above the ground. A second object with four times the mass of the first if released from thcr jpacr( m-,ju2(*jhe 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 endvn8wb/a d ,b/n7xo ni/ of a spring causes it to stretch 5.0 cm. If another 0.200-kg mass is added to the spring, the potential energy of the spring will b niobx /, /dn7n8a/bwve

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 mechanicalj bu,i aqql6(se;v2rl 88uc1u energy 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+cf5amv/5ne n kis,6w kinetic energy K, to its potential energe5,i6k cs+v nm w5fan/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 car driving upy ,5i;ax +newh 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 equal spxgou.iw,7 eg,+y.mug h/os grx 9.-ku eeds along a level frictionless surface. They ,ig.yx+mug/ghg9,ox-k. wr s.ou 7ueboth slide up the same frictionless 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 b7:f-ed5 cg3iyc 5uvh$m_{1}$ 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 conservatikd2x)9jl -*0 qfo yvdbve forces)*v ylk2d0bof9jqd- x.

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 ipty p i:22a-t*fwu en2s present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the pwt 2tu*y: epfn-pai22otential 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 3-6qn7 s, q zjhw,z1udpcdyr(- 0 J of kinetic energy. Do not ignore air resistance. How much gravitational potential energy did t c7w qz6s,hur,pyd-dj(1 z qn-he 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 dist-j pyo7r q ;,i0yn9thv*8/8tguby bkxance and loses 30 J of gravitational potential energy. Do not igy p/h gv0r;j87nkxbbu ot8qt-iyy,9 *nore 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 conservation of energyi3fsm3d ned4x3*uw e 4s cuj+9.

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 isr-hv j544fd. :fqd sn -6 3/flseeqkzq

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 uni3-y +e/ttf0gn- ekcm hts?

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 o b9nuoz +i5b*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 3 times the work in one-thirnvafeplc1* m l- o4di5j;am9 +d the time. To do so, em;9cvjlp5a+d*oima n f1 4 -lyour 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 9 8q;v)lpdsp nan;4hc at a constant acceleration, 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 ver s/*jkio bxifc2f)09atically 2.0 m and held there. If the object weighs 90 N, how much workaf 9* ci)jsbk0 f/2iox was done 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 u2e cfj.lw3ssa5xq g*/ p in the air a distance of 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by the wqw5*xsf s j3e2 clag./eight 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 constant force of 5500 :fup 4fthda6 i7e4g)9 0*ru vwu9elob N for a distance of 50.0 m. What is the work done by thtei 9uoguv4e4* )a0:6 fblrp fu7h9 wde 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 constant force of 5500 N for a distan,vk2x +bpauv9n/ - biwce of 50.0 m. What is the9v2, ipn/bubxvwka+- 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 2oftd5z9py+o2 x o+oha constant force of 5500 N for a distance of 50.0 m. What is the net work doneo x+d9zhoyt p+f oo522 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 auzn9,)yidn2 s( x/ oq2 uupa3glong 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;yx d j18l3iycfj0ob9 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 Sarah in a sled on ano4s u2mk8l wyud9.o *y icy surface (assume no friction)9k8om2ys . woy4*udlu, with 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 force. The graph in Fig:xq) vbdc *lqk :s)8ws. 6-1 shows the force versus the object's position. 8*:bwqc sd) q: )kvxsl 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 direction of thec1hc3* bnwu5g 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 4.0 mc 3ncuh1gb*w5.

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+*fs*atw zs*g gi kj sz6,73zj the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work do ** s,kjw6g3szj zf i+ta7*szgne 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 inj2e1mfe )w ra) Fig. 6-1 shows the force versus the object's position. Find the work done when the e1m weaf )jr)2object moves from 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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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 55-kg cartixlz qf)as; 9eh1sm57 (initially at rest) across a 10 m level surface. What is the final kine xslhm z5;eqa71)s9fi tic 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 m-5ip4;epc0nlxq+zh fb s2 u f(m d/1ntove a 55-kg cart (initially at rest) across a 10 m levesmc/q1bpt0f(+nx l ;u 2n5f4z-iehdpl surface. What 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 requ)yb zi4;bhc u0/3bufo mm at-.ired to stop the m uty.m/3m)ac-b;0hob iufz4b ass?

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 die 8s86 kgx(fidstance is required to stop a cardxf8ie6k(gs8 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 dart gun propels a 10-g dart. It is cocked 3.n.ngpq)ca hwf(fb3pi, ut 6by exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the ,u 6fnighpt3w (an. f.)cqb3pgun, 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 wcu/frqk0+p4q urv +;horizontal component of 80 N and a vertical component of 60 N. The force is applied to a box which rests on a level friction4 0uq+vrru/q+w ;kpfc less 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 horizowbttp sw9v 3(75d se jb11lv zzp29/dogux -k.ntally into a bale of hay, striking the hay with a bxd23(- jev9kz /t.b o7z1pd5sgwpt wl1u9 svvelocity of 60 m/s. It penetrates 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 above a floor to a cpu p(b42(.zip*kxpiheight of 13.0 m above txp u.4p(zi( bpp* ki2che floor. What is the change 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 plahnevv qtbko hjo )r76s ( c9cuz15.5:vne. The plane is 4.0 m long and rises 2.0 m. If the plane is frictionless, how much wovcc5u5bjoqth1kr s.zh97(o vne: )6 v rk 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 on8jwimoy eo:vd ,zkb-i; me:j3h eh2 35b)evb1to a spring, causes the spring to stretch 2.0 cm. What is the:b8;vizd ) 3bekjbwm :hyo-2v ,1meihj ee35o spring constant?

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 potential eiz l(o2,u0w8u u+hg t6+ftl qrnergy does it store, whentuqw0g,+uruh(li6 f82oltz+ 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 requiredy7j )ar - yf.abtqb eq3)r09epz/mvf( to compress an initially uncompressed spring with a sprin zbq )f9ama-e 3y.br y/eq( vtjp7r)f0g 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 kn 06k41y vwtrspring of spring constant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretchek tr1v04n6w ykd 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 amew):b w0nos7ra,81 a4md rqN/m is initially compressed by 3.0 cm. How much work is required to compress the spring7)8r nsaa:bq 104,rwm oedamw 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 from rest from the top of a 50-m hlm-bzr oovu:v0 k+o:8igh slope. What is the speed of the slier on reaching the bottom of tvo0 mb:+:r lozov8uk- he 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 k4ids +x;v; 2m/xzjq jdg, pushes off the top of a hill with an initial speed of 4.0 m/s. Neglectiqjj /d2idx4;v+ xmsz;ng 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 frictimy v2; 05 siq*6f,qlnjlemibdxk:62r onless inclined plane. At the bottom, it has a speed of 9 ,i b:v*6xqs2e5j0ld nry ;i6fm lk2mq.80 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 the floor, its potenv9uofscxd,z4 m+no(2) xb m62tb9vsdtial energy exmmd u+ ,bfxbtz v299x)vsncs ( 26o4doactly equals 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 kk y+bm k.z;v./kqsbg3z,+rh iinetic ener hvmb.z3kg .+ s,yq/+kbzi ;krgy of 40 J. At the exact top of its trajectory, 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 tb ;bofn6b- dbz3 hk,1qhe ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. 6,f qk 13bbn;db- zhboTo 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 diea+ lm i7q h+de:c+q+ap (See 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 th 7++ecqil ae mqah+d+:e 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 f 5lenp-h/hp.j)+u 6l/;a-e xk o- bgq0obg enat 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 slope, which is 30 m above the bottomfnn)-g 5opk0+ u h/he-qleoxlebap;/ g-6 j.b 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 boz.v(pef6v0s5f 6 t rzhtfy0)rttom 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,yz6sfvh (pezr).rf 5tvt0f60 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 ain 0fdfv 5xsz-..m,5 ty yj+cft 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 3xe,k,d4l:byv)dw n1 h6u u3na 0 cm away from the vertical axis and released from rest. What will be its speed at nh 1vklw6x , 4u u)n3ydabd:,ethe 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 un -n9ct vo) gb,kib*duk9/ b c ;cm+7xaxyw3l5lcompressed horizontal spring with ao-5l clb9w9unmc k7xd) +v ;bkcxb g3 ,/ti*yspring 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, sloj tog9j/ay0v9kt 48x8p oyy60im.sa tws down her 2000 kg car to stop for a red light. Wyioa 8y94j9k t0.8xavt s mtyp6gj/ 0ohat work is done by the 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 a 605 c*/q6x.86jb7qwon gpi/kkyqkij0p.0-kg object and a horizontal surface is 50.0 N. If the initial speed of the object/0/ ppkj5 7q6 i*xcqjqyiwkbk n86go. 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 rough, level surface. It has 24 J of kin8uboo4s 2 8)mpsw)xmt etic energy. The fri m88)x2puoomsbs tw4)ction 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 horizontally to a 2.0-kg mass on a cq cz, 6 ;ul:fga v h16lvzz,vqvr*a36level surface. The coefficient of kinetic friction be,6 v:zz lg*qv zl3;cvah6q 6rua1cvf, tween 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 fromk4i7mp1 8c o,ff rc-fp6pq:rj rest from the top of a 50-m high slope. If the work done by friction ir4 pm j1qf:f67 ckcp prf,o-i8s $-6.0 \times 10^{3} \; J$, 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. T pqsl (fgr,4(xhe plane is 4.0 m long and rises 2.0 m. It requires 3200 4q(plfx(,r sg J of 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 of a pla;v2xg fj p/hb(ne 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 vpxbg (f;/2hjmass 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 oflw1(w3d dp*bj 6bn:i w 10.0 m, and strikes the ground with a velocity of 7.00 m/sn* 6lpd3( :1 idwjwbbw. 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 siklca.ra tniji 8(y ( 5*wxq64tairs 10.0-m highxq86i.ay *5knia4t ri wclj((, 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 wmg o+7;ih9,/9r yecfmp.di imith a constant velocity of 5.0 m/s. What power must be delivered to the object by t+ir9mihe79op;m/ ,imdf yc . ghe 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 / ,b(cxf7xplaei +goyw6i ) m/runs for 1.0 hr? (1 hp/6ix,yg mf(l ba i/p7 co)x+we = 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 ratgh tlzs2x0 :lh4v21itv,6h jme of 500 W while riding. How much force does her foo glit:x1j hz2t4 s2v,hlhv6m0t push with 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 m/s in 7.0 s. What ul4)lrp3 ep * l*bu;jabzff;( is the average power delivered peu 3r)fjl**;4 fulp(bl;azbby the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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21	22	23	24	25	26	27	28	29	30
31	32	33	34	35	36	37	38	39	40
41	42	43	44	45	46	47	48	49	50
51	52	53	54	55	56	57	58	59	60
61	62	63	64	65	66	67	68	69	70
71	72	73	74	75	76	77	78	79	80
81	82	83	84	85	86	87	88	89	90
91	92	93	94	95

1	2	3	4	5	6	7	8	9	10
11	12	13	14	15	16	17	18	19	20
21	22	23	24	25	26	27	28	29	30
31	32	33	34	35	36	37	38	39	40
41	42	43	44	45	46	47	48	49	50
51	52	53	54	55	56	57	58	59	60
61	62	63	64	65	66	67	68	69	70
71	72	73	74	75	76	77	78	79	80
81	82	83	84	85	86	87	88	89	90
91	92	93	94	95

1	2	3	4	5	6	7	8	9	10
11	12	13	14	15	16	17	18	19	20
21	22	23	24	25	26	27	28	29	30
31	32	33	34	35	36	37	38	39	40
41	42	43	44	45	46	47	48	49	50
51	52	53	54	55	56	57	58	59	60
61	62	63	64	65	66	67	68	69	70
71	72	73	74	75	76	77	78	79	80
81	82	83	84	85	86	87	88	89	90
91	92	93	94	95