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

1#

What is the correct unit of work5fs5 h:ndg.frxo 7ou8q .v z0y 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 ix(vhxdb .db4(qxyil4 ez o 2*6s 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 stationary brick wall, the amount of work yo3f q4lq09oee 1ni/mt w,dk 7cg1i q/ eecmo9f l40dn gwtq37k,u do

A. doubles.

B. is cut in half.

C. remains constant but non-zero.

D. remains constant at zero.

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4#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 50-N object was lifted 2.0 m v -2t9ai0jn+b,z r9twh6m tihcertically and is being held there. How much work is being doatc j6 r+iht9wt2-9n m0bi,zhne 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 hor +yi0u(6bhg wfizontally forward at a constant velocity carrying a 10-N object, the amount of work you do isy(+6ib h0fu wg

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 verticallytu0 e2is4a5cg 3.0 m then returned to its original position. If the total weight 5gtau e0sc42 iis 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 on9av- qaln 5,ly 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 work done bg7 pq b /s:r.:en/bizly gravity while the ball goes up with the sign of the work done b slg . brq:z//inpb:e7y gravity while it goes down.

A. Work is + on the way up and + on the way down.

B. Work is + on the way up and - on the way down.

C. Work is - on the way up and + on the way down.

D. Work is - on the way up and - on the way down.

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9#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The area under the curve, on a Force versus position (F vs. x) graph, *c84 spy+,xscl f3py8 lc-d ccrepresentsy4s,c lx cp*dl y+3sc cpf88-c

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 positionxkvrr i0 wv*5spj* 1-e0w8)xo dv(lgk (F vs. x), what represents the work done by the forgo-1xdwk* 0sw xj5(k r plr80v*v vi)ece 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, iarv0u unt0 8myj2/(e*g/klc 3u; dhethen 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 done0 b oemi4/hng+hah 9s:.zhhg v+ -feeyma.+9h on an object is negative, then 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 a b9 h-blb(gda)n 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 twice the d7kc0 ,lj 4+ayfnv qd5speed of the car. Which statement is true about the truck's kinetic kdq y,a d0+cfvl7 4jn5energy 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 0sr8t.7-;nqtb,ecfkmncnu+ as car K, and car J has half the mass of car K. The kinetic energy of car J, compared to car +n,t;kmn. t7rceq80 bs-nf ucK 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. Wha 4 tj3 j-u;nugp7f8wwlt is the ratio of the final kinetic energy to the initial kinetic -pft; 7lw4uj8jn3uw g 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 s13;o h, m;h3ch-bu/s-ue 7ncra vpkcopeed of 5 m/s. If both objects have the same kinetic energy, what is the ratio of the brick's mass to the rock'sm;opbvc3 uh ,k3rh/- hc7ocu 1s;ean- 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 mgw5cg9 3ue4qi/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 trave549gu 3 ceqwigls 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 distxw9m,fjedrzo+ 9k 4 u/ance on a straight, level road. If you had been traveling twice as fast, what distancx,u99e4+wz/rf dmj ko e 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 anwb4y1:ld* jtw cidvugtl1t2zv3 q*77 elliptical orbit. Neglecting any friction effects, what hap1 ticlw u123bd:v yjwtlv*7d*zt47qg pens to the planet's kinetic energy?

A. It remains constant.

B. It increases continually.

C. It decreases continually.

D. It increases when the planet approaches the Sun, and decreases when it moves farther away.

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22#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the work-energy principle f0o/rhv+k2dy.

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 yw-1 n)gj9 ljgy*v/hvo1cdg6g af g1) negative potential energy?

A. Yes, as long as the total energy is positive.

B. Yes, since the choice of the zero of potential energy is arbitrary.

C. No, because the kinetic energy of a system must equal its potential energy.

D. No, because this would have no physical meaning.

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26#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object is released from rest a height h above the ground. A secoa8ir xy nk1x*4)kf9: vkop2hgj-j *i ynd object with four times the mass of the first if released)-* pay182kx9x oj4*vijfkgr :ny hki from the same height. The potential energy of the second object compared to the first is

A. one-fourth as much.

B. one-half as much.

C. twice as much.

D. four times as much.

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27#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.200-kg mass attached to the,n)m- ac5e np a.tqfe7 end 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 fnnce,5eq amp-a t). 7will 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 en-qvfu-cm: b4e+( qxr5) l; bpax;cy(w tqqr.gergy 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 potwc2w r *su kwbf6r)meq7xm8- )ential energy U.)8br u 2wcmwrex 6q-wk7 *f)sm

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 ;;qh+h,qo*r8.n 0 z ynmjkiehof 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 with equal spee-cvk: ol2 fgwphq,/ t(ds along a level frictionless surface. They both slide up the same frictionless hill. Whgf-o/:,(qc p vhkwtl2ich 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 mfcqd ;krc h0upcnh8*x27 7b5$m_{1}$ 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 conservative forces ork82q1p)+ 7tvkddrk . or71 tk2p vqd8rd+)kk

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 144hczcfliax n;.-y m(nx mr-the air (air friction is present), to the ground below. How does the kinetic energy (K) just befn(-cx l-m 4y;cxfh4 nmi.z 1arore 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 of kinetic energy. Do not ignorl ;mc: v6mn.zhe air rev :;ml hzc.nm6sistance. How much gravitational potential energy did the ball lose?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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36#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and loses 30 J of gravitational po(cn1q+ csllk8xjck :,x-2a v vtential energy. Do not ignore air resistance. How much kinetic energy :(lkq +-1xc,lkcxsv2cvja 8n 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 conservati.z o4) t suplgiis 5w;p+d,)fion 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 isfz1p1su ( -nue

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 b7 ygp07.vzp oexpressed 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;b(6*cm m qtnyun1r *d 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-third the time. To)ur2 u.w5 gusn do so, your power outpn.2uw) g5uu rsut 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 constant6(isquh-gex kw-pg- y47f7 qes*n ;wj 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 vertically 2.0 m akb/o-s zy 1a5qnd held there. If the object weighs 90 N, how much work was done z5bqk-1yao / sin 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 up in th,pv xc vi),cp,e air a distance of 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by the weight op ,cp)cxv i,,vf 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 7)avgg i jc*3gw* qy/2y dl5gzof 5500 N for a distance of 50lqga* gy j/yzv2ic7gwd)53g*.0 m. What is the work done by 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 constant force of 5500 N for a distbvps :z /+e ef;ty*ckgu;yn28ev8o/ u ance of 50.0 m. What is the work don/sbey otf/nz kvv;y2cee8*; g:+8u up e 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 of 5500 ga-78;+emxa vra y(lqN for a distance of 50.0 m. What is the net work done on the elevat;xae(a8qm 7a-+gryl v or?

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

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

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

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

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48#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30-N box is pulled 6.0 m up along a wq;kv*8izz7 u$37^{\circ}$ 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 w4lwtbx1z1x2;y tm0 o 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 an icy surfacrd x n.ypuv7p,i1z/fzwx:5k 4 9ghd)se (assume no friction), with a force of 60.0 Nd)gnxu5 ik1srz. 7d:y9vpwxfh, z/p4 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 objectpjp 8io(: co,: yvy8fohx:e w: in the direction of the force. The graph in Fig. 6-1 shows the force versus the objecjf(:oh cyx8 v::o: woey,ipp8t'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 fo xt2/icmq-yb9oa-qe2(29j- f qu+ 9flkuwdrg rce. The graph in Fig. 6-1 sh2uaqu9/tmlgr2+o- qk9y xf-2-c w die( jqb f9ows the force versus the object's position. Find the work done when the object moves from 2.0 to 4.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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53#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the 7e izp8;zh av1v lf6q:(ztc.xforce. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 4.ic(aez z761vzhp.f :8tx l;qv 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 tiszo9p eej ,:r:x (p2mhe force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 0 to 6.0 mrj m pzoi:2:,(seexp 9.

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 (initq:7vk/ 8gx j 2lbb2x *dnh k,iijlwd6/ially at rest) across a 10 m level surface. Whkbl8x dnb:q/2i/l ji6jd kgx, vw*27hat is the final kinetic energy of the cart?

A. $1.0 \times 10^{3} \; J$

B. $2.0 \times 10^{3} \; J$

C. $2.7 \times 10^{3} \; J$

D. $4.0 \times 10^{3} \; J$

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56#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A horizontal force of 200 N is applied to move a 55-kg cart (initiallhxy4fi;n :r+h y at rest) across a 10 m le h4x+ :fyn;ihrvel 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.5mcw5l*p 9 pes wgqwsi k5*d:/ How much work is required to stop the masd we/q 5lkp*w9* i5pcw m5:gsss?

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 ab njq*4mc8 t9k car initially moving at 25 m/s, what distance is required to stop a car moving at 50 m/s under the sameq*c8b t mj4kn9 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 byq(g9.yxdtnr09j2b-;ztgs gun propels a 10-g dart. It is cocked by exerting a force of 20 N over a distance o0y9nbg; (ytz-g.j dq2sbtr9x f 5.0 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 comp08imknpnv(1xu . +wt2f6jgp ponent of 80 N and a vertical 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 the cart's final kinetic en+.2nwi kf1p6gvp(t0 xu8m jn pergy?

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 intoxl w vderd(l,d)n)tiqr;sl/7suzlq )7d i,3- a bale of hay, striking the hay with a velocity of 60 m/s. It penetrates a depth of 20 cwe, llsldv);dr nuq)t)xsdqi7 3- lr(7,id/zm 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 heigh9)w,vc+tb.xvv jan tq g(2f t6iu))zs t of 7.00 m above a floor to a height of 13.0 m above theg u96 (nv)fab)+vtqs zt)w,vc2.ijtx 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 plane. .vyw*8h8 (tde dw-b cjThe plane is 4.0 m long and rises 2.0 m. If the plane is frictionless, how vje.88ddhc(- ytwbw *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,sipy v5sl ;a7) causes the spring to stretch 2.0 cm. What is the spr;iy7ss)5 p vlaing 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 potentii5g;n:att+o0 hzee9 a4vin 3dal energy does it storea3eza:t054+ g9idn oie vhnt ;, 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 springcm h9vi2rb .r6 with a rm2bi6c.r vh9spring 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 constant 40 N/m from x = 0wd/bdl9rcrewi:x 3 8bvmpq9q( t f2/ 3 ,jft+g.20 m to 0.25 m? (Assume the unstretched position iw /q89d3:e+p(b l,ff/ cdrqxt3rvtbi m2g9 wjs at x = 0.)

A. $0.45 \; J$

B. $0.80 \; J$

C. $1.3 \; J$

D. $0.050 \; J$

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68#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring with a spring constant of 15 N/m is initially compressed by 3.0 cm. -6r ilyuj 13 ukxukk/*How much work is required to co6 yku/k*iuljxu3r k1 -mpress 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 slod)mog,* a ici)em+5( cywdem1pe. What is the speed of the slier e1dc)c,ei+)y mgmao d mi*w(5 on reaching the bottom of the slope? (Neglect friction.)

A. 22 m/s

B. 31 m/s

C. 9.8 m/s

D. 41 m/s

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70#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A skier, of mass 40 kg, pushes off the top of a hill8ln6xk( y oz2ms4(uan with an initial speed of 4.0 m/s. Neglecting friction, how fast will she be moving after dropping 10 m in ele8sao xyz (ulm46(kn2n vation?

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 h9r 6xlhmrgh7 /as a speed of 9.80 m/s. What is the vertical/h 9rl7gxmr6h 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 abo+wy(b xd3x6uds .6m3r ramu .ove the floor, its potential energy exactly eqm3burod (s + .3yauxw6m6x.rd uals 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 kinetib,tmn mgv-/6(c;cslesh3r o / c energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140vcm-tn rle63/s,/;(b hsocgm 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 l n/vms; b5:hnz hlq9s9eaves the ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 b5 lzh: nq9h9s/nvs; mJ. To what vertical height, relative to its launch point, did it rise?

A. $\frac{220}{mg} \; m$

B. $\frac{120}{mg} \; m$

C. $\frac{100}{mg} \; m$

D. Impossible to determine without knowing the angle of launch

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75#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts from rest at a point 45 m *o 6;swmm /tt,x;d lxyum8e1qabove the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top x w 1e dl6mo*xm/sm;ty;qt8,uof the next slope, which is 30 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 17 m/s

C. 24 m/s

D. 30 m/s

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76#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts with a speed of 5.0 m/sag p h,nw;: ;eo7 jng4r,0tg9nf,xk)z aiuyg. at a point 45 m above the bottom of a dip (See Fig. 6-2). ,9gp nie.t;7gu,rk 0ygz);x ,g4fo:w nhj ana 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 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 of a dip wit2o tudl jo6;,jf.-ur eh a speed of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed o;r -ft odlo6e.j, uj2uf the roller coaster at the top of the next slope, which is 45 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 16 m/s

C. 18 m/s

D. 20 m/s

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78#

( 1.0 分) 切至整卷模式搜藏此题

What is the minimum speed of the ball at the bottom of its swing (po o1ja tau8tol7 : ue.2f-gr4tlqt58l sint

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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 reludyuzf.xb c.9u;o 7 rgf)h r;2eased from rest. What will be its specgfo yrh9u7);d 2xu.;f urbz.ed at the bottom of its swing?

A. 0.50 m/s

B. 0.79 m/s

C. 1.2 m/s

D. 1.4 m/s

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82#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car moving at 25 m/s hits an initially uncompresszvoarvc26dr8dr y m q45j:z73ed horizontal spring with spring constant of 3 d 627o:r4vmrz8dyzrcaqv5j$2.0 \times 10^6 \; N/m$. 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, l-xe pedhy 077slows down her 2000 kg car to stop for a red light. What work is lh0xed-7ye 7pdone 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 60.0-kg object and a horizontal surface i(qn ;i do b0k4xe;pr(bs 50.0 N. If the initial speed of the object px4d rko(b0i eq ;n(b;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. Ixrgdk(n,x1yz 0 ro5f; oq d6v7t has 24 J of kinetic energy. The friction for 5 nrqdzy,o 07k (61xdgrfovx;ce 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 horizontall8f55+ pqy sfyby to a 2.0-kg mass on a level surface. Thfyy55fsq+ 8pbe coefficient of kinetic friction 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 high41zkld0e d (y-wtt p-0*t*qa thrhx2 y slope. If the work don -t 2w *ap*l0y0(hqxtkh1zt -tdr4eyd e by friction is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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88#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An 800-N box is pushed u)d3)) sauio83na x6svvjp w:s p an inclined plane. The plane is 4.0 m long and rises 2.0 m. It requires 3200 J of work to get the box to thvo 3av:i8) nussxs)36 pa)d jwe 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 fryn g2egl n6y:ckz+0gan.8 xwe qt9-n3om rest at the top of a plane inclined at 20e above horizontal. The coefficient of kinetic cyytx aze90nlkg +.g8gn -n ew2:q6n3friction between the mass and the plane is 0.20. What will be the speed of the mass after sliding 4.0 m along the plane?

A. 2.2 m/s

B. 3.0 m/s

C. 3.5 m/s

D. 5.2 m/s

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90#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30.0-N stone is dropped from a height of 10.0 m, and strikes the ground with au 35 7w9,u jboewh9z6lufnd ;i velocity of 7.00 m/s. What averagelb9e96w 57hwzo f 3jn u;udui, 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 usin3zi5imas 4 1fgg energy when he runs up a flight of stairs 10.0-m hig af5i1g4s3 imzh, 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 needq/4k)ohg ( drned to move an object with a constant velocity of 5.0 m/s. What power must be delq)dro h/k4 (gnivered to the object 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 run(egm1g+e8 + ovndwp;hs for 1.0 hr? (1 hp = 7ndweegv(1 m 8 ghpo;++46 W)

A. $3.6 \times 10^{3} \; J$

B. $2.7 \times 10^{6} \; J$

C. $4.5 \times 10^{4} \; J$

D. $4.8 \; J$

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94#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A cyclist does work at the rate of ,oysfrq nyp1bd3;utb 7/8ta -500 W while riding. How much force does her foot pus /ft1y8bn ,;dart-p3uyboq7 sh 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:cr( 0rqbkjue 1ad v:di,:47ylrcuw: 7.0 s. What is the average power delivered by the engine? j: : byc0dc quwki,:rr:uv( edr1l74a(1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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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