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

1#

What is the correct unit of work expressed in SI-cvmjw3.qs.y .cu*jx 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 th96n 3e edeh+mcg 9sds*ere is no motion?

A. Yes, if an outside force is provided.

B. Yes, since motion is only relative.

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

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

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3#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If you push twice as hard against a,6s p elo8nvmb p1-m5e stationary brick wall, the amount of work yo6b8msl,nm 5p v 1e-poeu 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 v ie 2v u6j1.zx8x tpjgbob7+,2.0 m vertically and is being held there. How much work is beine1vzpbxj 6 ,x.j7t8g+ b2vuiog 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 horizontaraiubnm)y 5z* ).j:hvim2 gs* lly forward at a constant velocity carrying a 10-N object, the amount of )bmvz. m*ni*2hyg) 5asu:jriwork 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 verticall(xsn4 ymk- ha-0d kh1sy 3.0 m then returned to its original pos-hs hy(k- k0xsn4m1adition. 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 object do work px/7if 4 t78jsd+oyxo3x f-avon 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 work don/un6 oirdn ctq0-tz36e by gravity while the ball goes up with the sign of the work /-6oq 3cndzutrn ti0 6done 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. xii m8- p 0d.*yinmb5zw) graph, representsii5mydmb0 .8n*izp- w

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 work done byyf; u/xses/sc ,iz-qh o7y5 s: the force F?5yoshs7u /;z c,sif/q- xys:e

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'st6 oz+3wzigq4 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 object's kinegey wa yym 53:je3*7jjtic 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 n gkja60zuvzg).-9wlon an 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 car, and is moving at twicyvi(g3g ml1 1be the speed of the car. Which statement is true about thev3(gblg1y1 m i 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 has half the 5fvs7ci+n 4qh a-q+gv mass of car K. The kinetic energy of car J,qi4 h7n cgv+ +-qvasf5 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 aonisust a / :,r3s+w4 b*kebe/nd bounces back with half of its original speed. What is the ratio of th+osr3t e *b/ib ,w4/:kuassene 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 movin,5 s *ijwa yiv6m-;iv au0t.jag 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 th ujjw50t .ya -i6*;iaia, vvsme 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 movg:f a5dclk8q+k9+ iso ing with 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 dikk 9fi:+8lqc5asgo d+stance 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 brakes20pp wi t8w+i5h(t wfj of your car in a panic, and skid a certain distance on a straight, level road. If you had it+f w508piw2w (tjph been traveling 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 ellipticaled*9ndahyu /y5 7g0yh orbit. Neglecting any friction efgu9dyh*dha yyn7e/5 0fects, what happens 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 p x ,7o+pk;nj3jsuav 1orinciple.

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 enee.; as,st jgr8rgy?

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. 66a ,zn*jl/olu6aw im A second object with four times the mass of the first if released from thela,lu o im66n*zaj6/w 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 sp4+wh0givgb8eer26 hs ring causes it to stretch 5.0 cm. If another 0.200-kg mass is aegv0b + i62 egh4whrs8dded 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 energygece xs4g,mg :j/*(i v 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, to its po)g f*9qp zvo-v 6h0izrtential energyv*0 r9 -gzop)ivh fq6z 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 cartq0s,qw1:ng jskv )l / 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 arellw 3yoel:9/t ns; 2(s kwsz/l sliding with equal speeds along a level frictionless surface. They both slide up the sw3l9:/o ztn ;/lw(ys sll2kesame 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 ep +id n8,rtdzpg8mjw(/ l dzr5b998a$m_{1}$ 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 conservati8krgt3 z;b+1gr dv,slbu*-cn k dt4c 4on of mechanical energy for conservative forces.uzd,rl-;tnk 4b+8 rvs3tk1*g dc b gc4

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 t:kp)2(-ejpz4 mna gq30fjubs op of a building, through the air (air friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground com(eb0 s:jp3q-fm4zka2)p nu gjpare 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 distance and gaind1ga 9(k p.yz sdku+:fs 30 J of kinetic energy. Do not ignore air resistance. How much gravitational potential energy dsfd:dgkp 9ayz u+1k .(id 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 gravitational potentioef- 9:v;a8w:acnqh mal energy. Do not ignore air resistance. How much kinetic energy didmq-hona:w 9 e;c 8av:f 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 conservj6 y0c fv;+pudvyx i(0ation 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 isoi/a5quus7ask :4pm2

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 w:pg1my,hwm 7 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 poo nqgz3d74h 1k oh+-vfwer?

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 0-rf jl8l0q6ad: r d6roye1mq the time. To do so, yo06d1ef0y l8:d-6lqoj q rrarmur 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 ac u 2rww usg43l1r0f8afceleration, the car's engine must

A. maintain a constant power output.

B. develop ever-decreasing power.

C. develop ever-increasing power.

D. maintain a constant turning speed.

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43#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object is lifted vertically 2.0 m and held there. Iv .kzaquqw .9 mz0z 8f5opl/-bf the object weighs 90 N, how much work was don- lvm9b0qw.8/qakuz.f pz5z oe 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 boo c7woj/ 5gfm1znu61avk up 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 weight of the b/ wvam6g71un f 1zco5jook?

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 witr5zrn s5vtp ;puy y07.h a constant force of 5500 N for a distance of 50.0 m. What is the work done b;su r5z570typ. rvyn py the 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 ci/s)d5dl e n2ok ew2 ;ptfuk1t y*.tsxrky/0( onstant force of 5500 N for a distance of 50.0 m. What is the work done by the we*t.k2iudp (0xw/slofyn r )tk;1ye2/ked5 s t ight 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 constand rvdvz)9hfw( i1/h4 pt force of 5500 N for a distance of 50.0 m. What is the net workvdhrp14w )h /zvf(i d9 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 alon o9ljm6tzh thin5c8 , l p*i5lqgmb)86g 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 d8p*w+ u(rm xn7p 8+beafzmm) 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 anfk o +5p, no)aqmmt(.l icy surface (assume no friction), with a force of 60.0 N at an an(oop .)5k ,mam+l fqtngle 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 diresk85d9dm- isxction of the force. The graph in Fig. 6-1 shows the force vers- 8d59mskxsid us the object's position. 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 dire s-fvygeh0ez(qr 44+y1r. javction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 2-e0(s1 vqz. e4jr ar yg+v4hyf.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 forvxwr8o enj,af4l6awta.8 89o ce. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 8fa8, je oxr6tna9lw v.w4 a8o4.0 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 objuq ,91gorvu bi;cas h;.dy s75ect in the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Fiy;ha c;u9.7 gr s,1q o5sudvbind the work done when the object 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 cart (initially axn)bso0u3 +u+w +g igyt rest) across a 10 m level surface. What is the final kinetic energy of the gui+)b3y+ xous0n w+gcart?

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 carz bqs,-e7: aedt (initially at rest) across a 10 m level susq e a:dz,b-7erface. 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 required to st o at9q1qqpw2xui8 0 jk)/9gkoo1k/wu9qqj9)t a2iqx 0 gkpoo 8p the mass?

A. $50 \; J$

B. $75 \; J$

C. $100 \; J$

D. $125 \; J$

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58#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If it takes 50 m to stop a car initially moving at 25 m/s, what distance is reqf5zm e,7 66oxfuyob. kuired to stop a car momfb6 x,okfz6yeo7.u 5ving 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 i bv9ex:pm t+o 6 x+m lrb22ezzow-8-yfs cocked by exerting a force of 20 N over a distance of 5.0 bxwo2-:eevmp ++m2lt 8-b yorz69f zx cm. With what speed will the dart leave the gun, assuming the spring has negligible mass?

A. 10 m/s

B. 14 m/s

C. 17 m/s

D. 20 m/s

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60#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 100-N force has a horizontal component of 80 N and a vertical component ofjllg+s d1 z xu*0)fsm8ch8r5 m 60 N. The force is applied to a box which rests on a level frictionless floor. The ca hc *f ldjsm5glus8rz81x )+0mrt 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 horizontalney wj e;dr/nqo6o.8o--ceb;ly into a bale of hay, striking the hay with a velocity of 60 m/s. It penetrates a ecqbn8yj 6 oe-e; -;nod/o.wrdepth 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 h +5wr/iw 40hz )oy9bdyfrcb j/eight of 7.00 m above a floor to a height of 13.0 m above the floor. What is th4/woh50f jy9ry+cbd bz) w/i re 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 plane. Thybu2d 8lu*c si8ca(w3 e plane is 4.0 m long and rises 2.0 m. If the plane is frici(l 2u*8w8us3bca ydc tionless, 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 spring9,p8q : fpo )khnhrkou ,r91hm to stretch 2.0 cm. What is theuroh mq 9)fk1h,9p rk,8: noph 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 mui zz o.a-mbu;rkw0(, 6qns3a spring constant of 60 N/m. How much potential energy does it s6sn.za mb3 izow;q- m0, (urkutore, when 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 compress an initially uncompressed s4v5d+y/ezipr3 b*(r a p7nbk gpring with a spy 5+pab r/k n43igrzv(epb*7d ring 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 constar;-fq523t tbe a c0fkxxo9dl;nt 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstr-oef ;b509qck r2;t f3tad lxxetched 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 Nk e0f((cy q4kd/m is initially compressed by 3.0 cm. How much work is required to compress the spring an additional 4.0 cmk4d qeyc(k(f 0?

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 hv49 yvz+l ngt.igh slope. What is the speed of the slier on reaching the bottom of the slope? (Negleg 9.vn 4lt+vzyct 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 gr4vanbb*rf/pq( s glh.* e81off the top of a hill with an initial speed of 4.0 m/s. (rn b*q 4s pevgrhb*a.g8/1fl Neglecting 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 sg (ntg3wtloll 3 -:q:f1jicralo- /r /peed of 9.80 m/s. What is the vertical heig3 f 1o cn-ol-/tl/lg q wtirlja::(r3ght 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 8)w:dbvhh,n0 ny*x yc m above the floor, its potential energy exactly equals its kinetic energy. How fastd0yb h:* hwx y)ncvn,8 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 ve g2w10)ix fyz18yy k10 N, blasts straight up from ground level with a kinetic energy of 40 J. At the exact top of itswe2 18fiygx01y)zkv y 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 the ground wi9s-il g+ez qm9.qdo;e th a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To whates-ldgomq z e;.9 iq+9 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 rvfw+ k9md/ c1the 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, k+m9vd w/cf1 rwhich 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/ql koblr 5f:gh54v21ks at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect frictilhk:2rf45lkb 1voq5g on, what will be the speed of the roller coaster at the top of the next slope, which is 30 m above the bottom of the dip?

本题所包含的其它图片:

A. 12 m/s

B. 14 m/s

C. 16 m/s

D. 18 m/s

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77#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts at a point 30 m above the bottom 0c0lzujxe3 t61u :m+bvgy vzln5v ,6lof a dip with a speed of 25 m/s (See Fig0tv, :ey 0zm5 uvngl6ub3xzvl +6lc1j. 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 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 swin m9*,lqkh, mr0ip 6sxxjg):5 a+pzhjp g (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 d pjz qq+vgsfig1 pu+sw+.9pc,9ib )4the vertical axis and released from rest. What will be its speed at the iqs+. b)pqfp9i4dj 1zp + cu,gv+w9gs 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 a2 :6a ppt.met7wim8k w b8xe3vn initially uncompressed horizontal spring wtbv t6.m2 3waxw87p 8mp :eekiith 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 2000 kg car8j5mnw doja+p2:qky/ to stop for a red light. What work is done by the fridw 52:a /+pnymk8j qojction 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 60.0-kg object and a fw*g 77: q+atsbjryy7horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, w j7 sa*: tryfgw7+ybq7hat 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 onc- 4b19j:d ;m/duz+sm ob d3v(yddgub a rough, level surface. It has 24 J of kinetic energy. The frictiod(4ds9ozgdcyd;vdmjb3b 1u bu /-+m:n 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 horifc) t gbh-erdea;a:e jj, /6x+zontally to a 2.0-kg mass on a level surface. The coefficient of kinetic frictij:;bectghed-a 6x/e, )f ra+j on 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 from the top of a 50-m high sl56bc:mc0/a 0c+g ajrqg1 pvptope. If the work done by frictio1 m0agjcg:tpbq5vr0 +/ c6pc an 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:tq*- u-eh 3.m.cgl .fbjuhar 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 plane. What was the magh. -. caj .hulugb:efqmt3*r-nitude 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+t: qer8lb-e (tm-k ykne inclined at 20e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speed oftke( : yebm+ -qrl8tk- 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 heinn 7y1a5i66lv+zpm p h;xv.xoght of 10.0 m, and strikes the ground with a velocity of 7.00 m/s. What average force of ai.no1im7vx phpy6+;56z alnvxr 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 boy9 m,my2 g w1b(s mtc-:liz;e3)duorup using energy when he runs up a flight of stairs 10.0-m 3:)1 r2twl mimu cobspdm,9ez ygu( -;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 constant velocity of 5.0 m/s.h.atz*w3qp j8t,b g 7n What power must be delivered to the o7t a8p,z gjnw*q.h3 btbject by the force?

A. $0.50 \; W$

B. $1.0 \; W$

C. $50 \; W$

D. $100 \; W$

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93#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

How many joules of energy are used by a 1.0 hp motor that runwfm(nkw*zi 8oj ;,op 4s for 1.0 hr? (1 hp = 746 W)8*fpj ( mi wwzo;k4no,

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 whil .vozo lb/eh1,:tlnqa2 ;rqe1e riding. How much force does her foot push with when she is trloz; nthev.e 2r/1:1 qqlo,b aaveling at 8.0 m/s?

A. $31 \; N$

B. $63 \; N$

C. $80 \; N$

D. $4000 \; N$

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95#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s. What is the avn rn ,vje *op6te+,tm;erage power delivered jtr+ o;m,v,6 petnn*eby the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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