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

1#

What is the correct unitljcs80f 6:d;k f8b ei6n2 arrj of work 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 rw, p q16mrg7.abnoq,n qk);c 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 aga(18t0 oibp .wyk vywh:inst a stationary brick wall, the amount of work you do 8t yi.(0vpkow:hwb1 y

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 thiz, pkz-(rc q8xx r z**8j;jmkere. How much work is being done in holding the box in this** (jqi r zrkx-zzkjc;8,8mp x 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 ve4+oq zg:xev+2gww -oly0x 9illocity carrying a 10-N object, the2l x-i:w9qlo4o+xgezy +0 w gv amount 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 verticallo 6c:xb w-,pghy 3.0 m then returned to its original position. If the total weight is 30 N, how much work w -6b pcx,hwog:as 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 oej76 cn *7zc/rgeclm2n 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 sign8fub4 8dl 0xa2yokz ;m of the work done by gravity while the ball goes up with the sign of the work done by gravity w ab20umodf k;8xlz4y8hile 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 v, s,9gmor6z ioz um36hr4+d ylsm8u2os. x) graph, representsl 2m3ohd9i z6 ,s4,g um8my+rosru6oz

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 by +,zl u9l-4h2e ay:jq7 njfasnv 3*eqathe fo*hnjejaae f2zl9s n,+aq-l3y7vq 4u :rce F?

A. the slope of the curve

B. the length of the curve

C. the area under the curve

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

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11#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

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

A. the kinetic energy of the object.

B. the potential energy of the object.

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

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

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12#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an object is positive, then the 6z q etx *xqt7k.7xby8object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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13#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an object is negative, then the object's kinetic energy44aj1iyn5ckd(g; 6d5t oosui

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 onc mb6r 4xix,*c 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 a73ntm f6x; zout twice the speed of the car. Which statement is true about the truck's kinetic energy compared to that of thmno ;7ut63zxfe 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(klm(-1nbb*bmzu q ,i,(dl 2ff/ gncp K, and car J has half the mass of car K. The kinetic energy of car J, compare , fp/b2(cug*q-,nfl b( ld1bnzikmm (d to car K is

A. the same.

B. 2 to 1.

C. 4 to 1.

D. 1 to 2.

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17#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object hits a wall and bounces back with half of its original speed. Whauna 71371nmqq gmyb wump1)y+ t is the ratio of the final kinetic energy to qmm3p w) 7q1yy7umu1na n1gb+the initial kinetic energy?

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

B. 1/4

C. 2

D. 4

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18#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A brick is moving at a speed of 3 m/s and a pebble is moving at a speed of t lqpgf3s1a,s cu.l ):5 m/s. If both objects have the same kinetic energy, what is the ratio of the bqlss, ltu1 : ).gpcf3arick'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 ca+:ag hiv 6vm9oa6irf +1it*/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 maa r6+oi1 t vcgi+v*9h i:6aftravels the greater distance before stopping?

A. the 4.0-kg mass

B. the 1.0-kg mass

C. Both travel the same distance.

D. cannot be determined from the information given

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20#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You slam on the brakes of your car in a panic, and skid a certain distancpo,g7e 8 jy-tbe on a straight, level road. If you had been traveling twice as fast, what oe78 ,bg-pt yjdistance 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. Ne-mp 4i/s*k*i 8syqi61v uobmsglecting any frb*u/sp msm k6-vyi s*q8o1i i4iction effects, 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-energv u88n7o 0 54 xy a3,clp;utise15tneo qf6kjuy principle.

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 enerz.a ktqx3ky-zhl 3d(ip * x,4dgy?

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 heightw8m.evzxaim65rtlz s m, a92) h above the ground. A second object with four times the mass of the first if released from the same height. The potential energy of the second object compared to the firwmt mmx s 6 2.,zer9)a8zval5ist 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 endm4asf:m2 9gpc of a spring causes it to stretch 5.0 cm. If another 0.200-kg mass is added toa4p 2:cmm9gfs 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 of +5xng9tzwuax5b6 o)f*doc ;d 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. Compar ;mk4r1jan/y de its kinetic energy K, to its potential energy jkrnam y;/41 dU.

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 bk+jmou n faxm,4 66j(of a car 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 5qm8s.q 9k0imxgs )zv/w b2yy with equal speeds along a level wy b/smvz9q58yi 0gk)qms.2x frictionless surface. They both 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 +y u-t 5e:h.veq8xs ct$m_{1}$ 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 conservativebhv 2gg(:td5h forces(t5hvg dh2g:b.

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 qn p2wz :qm(.o1 *depxis present), to the ground below. How does the kinetic en:.d2( 1 oxpmqqe pw*znergy (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 distance and gains 30 J orfh.o4+.t mi pf kinetic energy. Do not ignore air resistance. How much gravitational potential energy did the ballpf.+th 4im.or 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 distance0s,d8/ xihm wm rxv+5 w2j(abh and loses 30 J of gravitational potential energy. Do not ig8x vib0rmh ,w25(x smw/j +hdanore 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 conservag(yahztz dy qml0 w) *,50h kgbj)/,mvtion 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 isrn)6 bq4c)iba

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 ajo+j3. hvuz.)akv7yunit of power expressed in SI units?

A. $kg m/s^2$

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

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

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

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40#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Of the following, which is not a unit5n;iopbj ,ni -d(o0 tr17tmrx 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-;o :uq0ikq5:hq3yj;n* yuywdv(-l oxthird the time. To do so, yo:hvqw3jl o *i-q5 0:(ukyqx;dyy on; uur 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 acceleration9aav vjde u5-9, 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.eb/j p 7x g3snjm60eb20 m and held there. If the object weighs 90 N, how much work was done in liftinj3gbnbsm607px j/ e2 eg 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 bol os2y:fbe4ekbs l wkle7kki-+a()5.ok up in the air a distance of 1.0 m, at a constant velocity of 0.50 m/s. What i5kweel : .af(+)obkye lb 274s sk-lkis the work done by the weight of the book?

A. +10 J

B. -10 J

C. +5.0 J

D. -5.0 J

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45#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upp ;a) qo.i:vpdward with a constant force of 5500 N for a distance of 50.0 m. What is the work done b:ap.dpi oq)v ;y 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 0 el;h:lf. hlrpulled upward with a constant force of 5500 N for a distance of 50.0 m. Wha:0.fhllhr;l et is the work done by the weight of the elevator?

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

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

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

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

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47#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward with a constant force pp mr1aq9-- cb nsaxj)-u:cuv teg821 of 5500 N for a distance of 50.0 m. What is the net work qataxusb)nvcep:8cu-g -1p-1m9j2r 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 alongiwa2 . 4ht( hbuf51r tl5rd,ii 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 qkv cd1o q-2fi)y( a(xdown 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 a v; ,f(2cnf: lnmry4ajn icy surface (assume no friction), lm(cnf v4;,: nafr2 jywith 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 Fii4 ;1 g y0clhetncwkf(o8r) 1fg. 6-1 shows the force versus1cfh) r84wc fy10noi (ket ;gl 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 direction of the force. be)99dl zi ,tg:b n6uk The graph in Fig. 6-1 shows the force versus the object's position. Find the work dok) ubt6i ,z 9:bedngl9ne 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 the5i (ido0 kdvybat8- xnx889 :fdu*alh direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when ybk- 9 8txadanv*f u:d0ilhi(8o5d8x the object moves from 4.0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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54#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the force. The graph in Fig. 6-1 shzw5 vdgv n r8w*10)tihows the force versus theg0w1ir*)dn wh5 v t8zv object's position. Find 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 at r;d2lsipkc b+ c:b.tb *est) across a 10 m level surface. What is the final kinetic enerskc.:pc +bl;bd2i*b tgy 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 appl1w x -kt iawp6)*zzk48nvb-dbied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final speedtdpkx1-a b86ibkwznw- v4z *) 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/mi,pq-i 0k zmir5b8s5s. How much work is required to stop th rb i5p,8sk50im iq-mze 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 dq,1+wjqnw 4f;ak i8cpistance is required to stop apanq 4w iq+j c;8kwf1, car 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 bvytj0e4w4 pbxsp0 bg 40hxy)3(nx i (xy exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave pnp 0( vy) e tgxbwjyh00(bx3s44x4xithe 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 vertica 9)rtzbgr7l+bevakccz:8h f(o+h2y8l component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 m horizontally along the floor. What is 82 7of+ le(89kabch:hvrty)gzc+rzbthe 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, sjypy t37sm 0+btriking the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What is the average stopping force acting30 s+p mjyt7yb 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 above9pd9kl6v 2zi n-q0 jdm a floor to a height of 13.0 m above the floor. q-dip996n dzk0m vl2j 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 plane. The pltd69 mj-pv kjzp+85u jane is 4.0 m long and rises 2.0 m. If the plane is frictionless, zjd6-8 uvj pk9pt+5jmhow 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 spring to stretch 2.0 cm. 9 0syg,s: luoor(ykh8hdg( c;What is the sprog 9hcus :do(h ,slyr;y0kg (8ing 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. Haix 1(ea4 yog.ow much potential energy does it store, ig4.yxo ae (a1when 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 initial)4u hm+0wz 4ltt tg/((xgfbivly uncompressed spring with a spring cons+ gf0t(ituhx( mv)b/ t4w l4zgtant 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 constant 40 N/m fvipf 9-j xl /)n10 ,vhougd*ourom x = 0.20 m to 0.25 m? (Assume the unstretched position of*0 /i-dpuj 1xgvnlv o9h,u)is at x = 0.)

A. $0.45 \; J$

B. $0.80 \; J$

C. $1.3 \; J$

D. $0.050 \; J$

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68#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring with a spring constant of 15 N/)g v(uv0gv4e zm is initially compressed by 3.0 cm. How much work is required to c(u)e0 gvzg 4vvompress 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 from rest from the top of a 50-m high slope. What is tuk m4fr an7*bl :,/p azemcu(new7g65he speed of the slier on reachca5p(nem n/7gf alk:weum4u7z*, br6ing the bottom of the slope? (Neglect friction.)

A. 22 m/s

B. 31 m/s

C. 9.8 m/s

D. 41 m/s

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70#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A skier, of mass 40 kg, pushes off the top of a hill with an7(h (fcvcz-po initial speed of 4.0 m/s. Neglecting friction, how fast will she be moving after dr7- cz(chv(p ofopping 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 frictionlesszs z almn0q6cim-7yt bq.f 8/, inclined plane. At the bottom, it has a speed of 9.80 m/s. What is the vertical height8 z by6,7cqn-a 0qilz m.t/smf 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 floos or1+d)tmm/ pgh; h;xaw)jjbqp 8.t4r. When it is 0.70 m above the floor, its potential enp)xhjdo r+mhtgj ;a1;q bp).w4t/ m 8sergy exactly 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 gwsg3l e i;j;3cud x nr1m4tw+lf6v56 fround level with a kinetic energy of 40 J. At the exact top of its trajectory, itsw i643rn; +d5tm 3sfv fluw l16gcxej; 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 with a kinetic energy of 220 J. zm *2qwl a .la.mps*iy/2zgx0 At the highest point in its trajectory, its kinetic energy is 120 J. To what vertical height, relative to its launch point, did it rise?l/a 0 .2zwiqys*m 2gm.*pzlax

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 (See.82 tijs3 mh;;sx v:n mgy0lmq Fig. 6-2). Neglect friction, what will be the speed of the roller coaster am:g0.s; t iml x8v3y;jmhs2qnt the top of the next slope, which is 30 m above the bottom of the dip?

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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 bottom,8aorvgewhhxh w7)r* ot2 0 q8 of a dip (See Fig. 6-2). Neglect friction, what will be the rqha0rw2w o7o)8*hthgexv ,8 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 abov k;.f5e3k2 irjrtzhy3e the 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 nexjitkhz. er;533 kr fy2t 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 nku/,vr6 w g:gthe ball at the bottom of its swing (point

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79#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A:2.2 m/s

A. 3.1 m/s

B. 4.4 m/s

C. 4.9 m/s

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80#

( 1.0 分) 切至整卷模式搜藏此题

难度:2

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81#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A pendulum of length 50 cm is pulled 30 cm away from the vertical axis and reltl/rc0p * 4mdba +95wsyjic* weased from rest. What will be its speed at the bottom p*+ycs0j5*d b9w/ at rcmlwi4of 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/gp t9r- zug9 i:ru/jw(s hits an initially uncompressed horizontal spring with spring cons:igw9ztru- gjp(9 u/ rtant of $2.0 \times 10^6 \; N/m$. What is the maximum compression of the spring? (Neglect the mass of the spring.)

A. $0.17 \; m$

B. $0.34 \; m$

C. $0.51 \; m$

D. $0.68 \; m$

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83#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A driver, traveling at 22 m/s, slows down her 2000 kg car to stop for lur+ctx t2(w5zq;9gf t7 9nsna red light. t c2f 5s( tgnzl w9tru7q9x+n;What 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 60.:frtoo g(;c i31cn fo:ldu-l/a 6qs+u0-kg object and a horizontal surface is 50.0 N. If u:6-c1oo+ gofal(ilrq ftd:u/c 3; nsthe initial 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 rough, level surface. It has 24 J of kineticj w7p4 w1.mgls energy. The friction force on itw14gwl7.sm jp 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 2s7dfw7eu ef4 2m dum;shfd+nc.m; z1,.0-kg mass on a level surface. The coefficient of kinetic friction between the mass and the surface is 0.2w1fsdzc+f 7,ue df;4 n2mmsd7e. m uh;0. 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 work dm3.n 8 zaq0 /vcwp5rpaone by frictnrvpw8a.qam0 zp35 / cion is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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88#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An 800-N box is pushed up an inclined plane. The plane is 4.0 m lonafv)cz(q- kd7o 2z91 :erb pljg and rises 2.0 m. It requires 3200 J of work to get the box to the top of the plane. What was the magnitude of the average friction forcblq jr(o72 cz):1e9 apz vkf-de 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 amzpj f5h;rx09 plane inclined at 20e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speed of the mass after sliding 4.0 m along rjh5 p9m;0fxzthe 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, n0(tm(k nvcmyh9y6y5 and strikes the ground with a velocity of 7.00 m/s. What average force of vty0c n(m(hy695y nmk 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 r/,)oq5 sele p58jpyl6cy 8ujfuns up a flight of stairs 10.0-m yluojsfjq5/6,l8 c8e yp)5pehigh, 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 velos-; 7*1qzej w -haa9whyeefcq ,uy8v br s34e;city of 5.0 m/s. What power must be delivered to the object b-e cqz9hy ; s1fay3e j4 vhaswe qerb-uw78,*;y 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 ene2 x dq4m9//8l srbbvgzrgy are used by a 1.0 hp motor that runs for 1.0 hr? (1 hp = 746 W) vs8q2dx bm 9gb/rzl4/

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 while riding. How much force doxkfr/kv,mbz w31u(+k es her foot puxf+mu /b3r( vzk1wk,ksh 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 2l.rp qow+ k:23k2ksgr5 m/s in 7.0 s. What is the average power delivered by the engine? (1 hp = p3kr2gl+ o2 sqrk:. kw746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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