Physics Unit7: Linear Momentum - 51fly国际课程 (51fly.win)

1#

What is the SI unit of mome8dyt af; 68i six9r+7esw b)c/h5 alzintum?

A. Nm

B. N/s

C. Ns

D. N/m

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2#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

When a cannon fires a cannonball, the cannon will recoil *koz.u(v l4t9 nyh:4c5k vgky backward because the

A. energy of the cannonball and cannon is conserved.

B. momentum of the cannonball and cannon is conserved.

C. energy of the cannon is greater than the energy of the cannonball.

D. momentum of the cannon is greater than the energy of the cannonball.

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3#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A freight car moves along a frictionless level railroad track at ctq 1m.0,+m fce bv*ulbewsy /*onstant speed. The car is open on top. A large load of coal is suddenly dumped into the car. What happens to the ve *.mvq +blwy/eum,1*0s b cftelocity of the car?

A. It increases.

B. It remains the same.

C. It decreases.

D. cannot be determined from the information given

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4#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A child falls sideways off a sled while sledding on frictionless ice. What hahj-rx b1i7 xb17a9bunppens to the velocity of b1jx-ar9uh71xnb7i bthe sled?

A. It increases.

B. It remains the same.

C. It decreases.

D. cannot be determined from the information given

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5#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A rubber ball and a lutf 2cic 7 u4;iud8gzx1mp of putty have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same spe14i xuz 7fuct ;82idgced with which it hit. The putty sticks to the wall. Which objects experiences the greater momentum change?

A. the ball

B. the putty

C. Both experience the same momentum change.

D. cannot be determined from the information given

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6#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A sailboat of mass m is ma g bc6ekles4ng21p83oving with a momentum p. How would you represent its kine8a4kle ncpg3ebg1s 62tic energy in terms of these two quantities?

A. $p^2/2m$

B. $\frac{1}{2} mp^2$

C. $mp$

D. $\frac{1}{2} mp$

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7#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If you pitch a baseball with twice the kinetic energy you gave 0b)1( fflidwlit in the previous pitch, the magnitude of its momen bl1fw0if( )ldtum is

A. the same.

B. 1.41 times as much.

C. doubled.

D. 4 times as much.

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8#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State Newton's second l9gly4k-4hvj g/,evbc aw in terms of momentum.

该题自我估分: (必填) (满分:1.0分)

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9#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the law of conservation of mon m8xa)scyl69 mentum.

该题自我估分: (必填) (满分:1.0分)

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10#

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 time 8q2)9rdtxx.-vsih yl (F vs. t) graph represents

A. impulse.

B. momentum.

C. work.

D. kinetic energy.

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11#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Which of the following is an accurate statemsdtt ntf(/9sm24d kn: ent?

A. The momentum of a projectile is constant.

B. The momentum of a moving object is constant.

C. If an object is acted on by a non-zero net external force, its momentum will not remain constant.

D. If the kinetic energy of an object is doubled, its momentum will also double.

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12#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A small car meshes with a large truck in a head-on collisit n t7ax;,hb9qon. Which of the following statements ctaq9n;7bt h,xoncerning the magnitude of the average collision force is correct?

A. The truck experiences the greater average force.

B. The small car experiences the greater average force.

C. The small car and the truck experience the same average force.

D. It is impossible to tell since the masses and velocities are not given.

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13#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Two equal mass balls (one red ady-xdxsc88j:75knip q2l18kr bf g 9lnd the other blue) are dropped from the same height, and rebound off the floor. The red ball rebounds to a higher position. Which ball is subjected to the greater magnitude of impulse during its collision wgn2 8 xkbildc1:dyp fl8-jkq59 x8rs7ith the floor?

A. It's impossible to tell since the time intervals and forces are unknown.

B. Both balls were subjected to the same magnitude impulse.

C. the blue ball

D. the red ball

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14#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A Ping-Pong ball moving east mkwbl2c9m*+fat a speed of 4 m/s, collides with a stationary bowling ball. The Ping-Pong ball bounces back to the west, and the bowling ball2l*f9mck bmw + moves very slowly to the east. Which object experiences the greater magnitude impulse during the collision?

A. Neither; both experienced the same magnitude impulse.

B. the Ping-Pong ball

C. the bowling ball

D. It's impossible to tell since the velocities after the collision are unknown.

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15#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Two objects collide and bounce off each other3vd :68mtk offuuq;q8. Linear momentum

A. is definitely conserved.

B. is definitely not conserved.

C. is conserved only if the collision is elastic.

D. is conserved only if the environment is frictionless.

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16#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 3.0-kg object moves to the right at 4.0 m/s. It collides head-on wiif15ikmuep4g 47 gg 0mth a 6.0-kg object moving to the left m7ikp u5e ggim gf4104at 2.0 m/s. Which statement is correct?

A. The total momentum both before and after the collision is 24 kgm/s.

B. The total momentum before the collision is 24 kgm/s, and after the collision is 0 kgm/s.

C. The total momentum both before and after the collision is zero.

D. None of the above is true.

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17#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 100-kg football linebacker moving 2 m j,.xod bgk7qmu8s8at 2.0 m/s tackles head-on an 80-kg halfback runni,m2jko8bdx g sm7q8.ung
3.1 m/s. Neglecting the effects due to digging in of cleats,

A. the linebacker will drive the halfback backward.

B. the halfback will drive the linebacker backward.

C. neither player will drive the other backward.

D. this is a simple example of an elastic collision.

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18#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

In an elastic collision, if the momentum is conserv.:0gf x naj: z, 9mn.j6.eaja4 ukzknned, then which of the following stjagj anf ,0k ne.n 9xn: .6j.amu4zkz:atements is true about kinetic energy?

A. Kinetic energy is also conserved.

B. Kinetic energy is gained.

C. Kinetic energy is lost.

D. none of the above

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19#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

When is kinetic energ q1ygbl,ua;b)y conserved?

A. in elastic collisions

B. in inelastic collisions

C. in any collision in which the objects do not stick together

D. in all collisions

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20#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

In a game of pool, the white cuhbr*t65rjl. rs5 wfs 69cz1jie ball hits the #5 ball and stops, while the #5 ball moves away wihi5jstjb9*r1r z6 csl6 . rw5fth the same velocity as the cue ball had originally. The type of collision is

A. elastic.

B. inelastic.

C. completely inelastic.

D. any of the above, depending on the mass of the balls.

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21#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

When a light beach ball rolling with a speed of 6.0 m/s collides with a heavy ex u/9h,4wvjhb zercise ball at rest, the beachwzhu4 b/9j,v h ball's speed after the collision will be, approximately,

A. 0.

B. 3.0 m/s.

C. 6.0 m/s.

D. 12 m/s.

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22#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A golf ball traveling 3.0w/hke ft 1r55 w4zgnr2 m/s to the right collides in a head-on collision with a stationary bowling ball in a friction-free envi2w/hge r4w1rk5tzf 5nronment. If the collision is almost perfectly elastic, the speed of the golf ball immediately after the collision is

A. slightly less than 3.0 m/s.

B. slightly greater than 3.0 m/s.

C. equal to 3.0 m/s.

D. much less than 3.0 m/s.

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23#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A rubber ball with a speed of 5.0 m/s collides head-on elastically with a6l7ij qw8n t9rn identical ball at r6i8rl97j nqwt est. What is the speed of the initially stopped ball after the collision?

A. zero

B. 1.0 m/s

C. 2.5 m/s

D. 5.0 m/s

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24#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A very heavy object moving with speed v collides head-on)b fxpw b 7m 37lkk5pj:dm4ne o607hqc with a very light object at rest. 67e:p c l5bxkqho )mp740f7mwdk nb3 jThe collision is elastic, and there is no friction. The heavy object barely slows down. What is the speed of the light object after the collision?

A. nearly v

B. nearly 2v

C. nearly 3v

D. nearly infinite

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25#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A very light object ohz s 1(2*m;ibx*wscers *qf8moving with speed v collides head-on with a very heavy object at rest, in a frictionless environment. The collision is almost perfectly elastic. The speed of the heavy object after the collision ii ( ss*z*f;em sb2*hoxc18wqrs

A. slightly greater than v.

B. equal to v.

C. slightly less than v.

D. much less than v.

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26#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A red ball with a velocity of +3.0 m/s collides head-on with a yx jt0mg2xsx2llm+ txx49 /1j pellow ball of equal mass moving with a velocity of -2.0 m/s. Wha/t4 j1s9m+0x xgt2x x2pjmx llt is the velocity of the yellow ball after the collision?

A. zero

B. +3.0 m/s

C. -2.0 m/s

D. +5.0 m/s

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27#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A very heavy object moving /2ji5 -i4jv6z fjsjm yng7x8:hkaom; with velocity v collides head-on with a very light object moving with velocity -v. The collision is elastic, and there is no friction. The heavy object barely slows down. What is the speed of the light object after the collisio :j nf5ao87-sjj i2yk6ijg hxzmm4;v /n?

A. nearly v

B. nearly 2v

C. nearly 3v

D. nearly infinite

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28#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

In an inelastic collision, if the momentum is conserved, then which of the folqxa6q;u 8 7rarlowing sr6q8 xr7uaa;q tatements is true about kinetic energy?

A. Kinetic energy is also conserved.

B. Kinetic energy is gained.

C. Kinetic energy is lost.

D. none of the above

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29#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Two objects collide and stick togetherc/o4 h+yj8u9d zrdub:4n*/ git (yn bg. Kinetic energy

A. is definitely conserved.

B. is definitely not conserved.

C. is conserved only if the collision is elastic.

D. is conserved only if the environment is frictionless.

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30#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 3.0-kg object moves to the right at 4.0w6 bxq3 d2qi/x m/s. It collides in a perfectly inelastic collisioxx23w qd/6bq in with a
6.1 kg object moving to the left at 2.0 m/s. What is the total kinetic energy after the collision?

A. $72 \; J$

B. $36 \; J$

C. $24 \; J$

D. $0 \; J$

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31#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A small object collides with a large8k(gb4ra4 dd hm0sx(pv5d; at object and sticks. Which object experiences the larger magnts( v;d5 pka4 (x408dga bhrmditude of momentum change?

A. the large object

B. the small object

C. Both objects experience the same magnitude of momentum change.

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

In a game of pool, tjnuw7:3 xbyxy,w59hz zm/ 8il sbm z29he white cue ball hits the #9 ball and is deflected at a $35^{\circ}$ angle to the original line of motion. What is the angle of deflection below the original line of motion for the #9 ball?

A. $35^{\circ}$

B. $55^{\circ}$

C. $75^{\circ}$

D. $90^{\circ}$

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33#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Consider two unequal masses, M and m. Which of the following stata 9k;p3aky m-qements is falsm -a9ykpa 3q;ke?

A. The center of mass lies on the line joining the centers of each mass.

B. The center of mass is closer to the larger mass.

C. It is possible for the center of mass to lie within one of the objects.

D. If a uniform rod of mass m were to join the two masses, this would not alter the position of the center of mass of the system without the rod present.

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34#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Which of the following is a fzz*7kv( iosgycm 2u.e +kv;)wd3,lby alse statement?

A. For a uniform symmetric object, the center of mass is at the center of symmetry.

B. For an object on the surface of the Earth, the center of gravity and the center of mass are the same point.

C. The center of mass of an object must lie within the object.

D. The center of gravity of an object may be thought of as the "balance point."

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35#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Tightrope walkers walk with a long fe+y0x jjl1 f*lgg(o*a lexible rod in order to

A. increase their total weight.

B. allow both hands to hold onto something.

C. lower their center of mass.

D. move faster along the rope.

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36#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A plane, flying horizontally, re.ji- ;e 7luhktleases a bomb, which explodes before hitting the ground. Neglecting air resistance, the center of ma.i;et- u7hkljss of the bomb fragments, just after the explosion

A. is zero.

B. moves horizontally.

C. moves vertically.

D. moves along a parabolic path.

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37#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Two cars collide head-on on a level friction-free qhimjlqw8973r2l7 r c road. The collision was completely inelastic and both cars quickly came to rest during the collision. What is true about the velocity of this sqhqw2c7rr8m3j il7 l 9ystem's center of mass?

A. It was always zero.

B. It was never zero.

C. It was not zero, but ended up zero.

D. none of the above

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38#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State Newton's second law for a system of partiffh8 y;ak6mo30lpn *pcles.

该题自我估分: (必填) (满分:1.0分)

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39#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What is the momentum of a 2000-kg tn*: vpdub9c5 uruck traveling at 35 m/s?

A. $57 \; kg \cdot m/s$

B. $3.5 \times 10^{4} \; kg \cdot m/s$

C. $7.0 \times 10^{4} \; kg \cdot m/s$

D. $7.0 \times 10^{5} \; kg \cdot m/s$

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40#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1200-kg ferryboat is moving south at 20 - uiqyt7a1h1i m/s. What is the magnitude of its momeqa1t1yiuhi -7ntum?

A. $1.7 \times 10^{-3} \; kg \cdot m/s$

B. $6.0 \times 10^{2} \; kg \cdot m/s$

C. $2.4 \times 10^{3} \; kg \cdot m/s$

D. $2.4 \times 10^{4} \; kg \cdot m/s$

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41#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball of mass 0.10 kg is dropped from a he ;uv vdod)p5mkdfa3./ight of 12 m. Its momentum when it strikes the ground iv3dam/ ovk)df5.u ; dps

A. 1.5 kgm/s.

B. 1.8 kgm/s.

C. 2.4 kgm/s.

D. 4.8 kgm/s.

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42#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Two identical 1500-kg cars are moving perpendicular toqs9zspu9y(tdczomxidf/ / s :da)6; ; each other. One moves with a speed of 25 m/s due north and the other moves at 15 m/s due east. What is the total momentumss/fomiuca)ts9/d z ;d 9 zpx;6q:dy ( of the system?

A. $4.4 \times 10^{4} \; kg \cdot m/s$ at $31^{\circ}$ N of E

B. $4.4 \times 10^{4} \; kg \cdot m/s$ at $59^{\circ}$ N of E

C. $6.0 \times 10^{4} \; kg \cdot m/s$ at $31^{\circ}$ N of E

D. $6.0 \times 10^{4} \; kg \cdot m/s$ at $59^{\circ}$ N of E

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43#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A handball of mass 0.10 kg, traveling horizontally at 30 m/s, pr0 w*kb+ewi) strikes a wall and rebounds at 24 m/s. What is ti 0bww+kpre*)he change in the momentum of the ball?

A. 0.60 kgm/s

B. 1.2 kgm/s

C. 5.4 kgm/s

D. 72 kgm/s

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44#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.060-kg tennis ball, initial uru.r15a1r2lbn *k7 6c j:(ytgojofwly moving at a speed of 12 m/s, is struck by a racket causing it to rebound in the opposite direction at a spej trfl rujga1. r*o5nw1 buo2kc:(67y ed of 18 m/s. What is the change in momentum of the ball?

A. 0.36 kgm/s

B. 0.72 kgm/s

C. 1.1 kgm/s

D. 1.8 kgm/s

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45#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 50-kg pitching machine (exc4kf oe+ays/ y6qqpm*(- nem1u luding the baseball) is placed on a frozen pond. The machine fires a 0.40-kg baseball with a speed of 35 m/s in the horizontal 46em+f -1 (*epyyknqmu/aoqsdirection. What is the recoil speed of the pitching machine? (Assume negligible friction.)

A. 0.14 m/s

B. 0.28 m/s

C. 0.70 m/s

D. $4.4 \times 10^{3} \; m/s$

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46#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 70-kg astronaut is space-walking outside the8i8gvdjd)uk r.ta,l-4kxwi,c/ a2 ku space capsule and is stationary whex8i-)jd,wli2au8ckk. at r kg,u4vd / n the tether line breaks. As a means of returning to the capsule he throws his 2.0-kg space hammer at a speed of 14 m/s away from the capsule. At what speed does the astronaut move toward the capsule?

A. 0.40 m/s

B. 1.5 m/s

C. 3.5 m/s

D. 5.0 m/s

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47#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A small object with momen-aoh -xgyvbr n7d2,::js unr4tum 5.0 kgm/s approaches head-on a large object at rest. The small object bounces straight back with a momentum of magni4d vjn y,sx-grb:h-ao7n: r u2tude 4.0 kgm/s. What is the magnitude of the large object's momentum change?

A. 9.0 kgm/s

B. 5.0 kgm/s

C. 4.0 kgm/s

D. 1.0 kgm/s

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48#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You (50-kg mass) skate on ice at 4.0 m/s to gcvp2 ny*-.kys reet your friend (40-kg mass), who is standing still, with open arms. As you collide, while holding each other, with what speed2 .*yckps vy-n do you both move off together?

A. zero

B. 2.2 m/s

C. 5.0 m/s

D. 23 m/s

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49#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A car of mass 1000 kg moves to the right along a level, 8n 80pk8d -i ialdnn7cstraight road at a speed of 6.0 m/s. It collides a 8inik 8d-p870lcndndirectly with a stopped motorcycle of mass 200 kg. What is the total momentum after the collision?

A. zero

B. 6000 kgm/s to the right

C. 2000 kgm/s to the right

D. 10,000 kgm/s to the right

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50#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1000-kg car traveling at 25 m/s r vl::;emf ftl u;8fe. 5v)z/m d5ksj3zame9hluns into the rear of a stopped car that has a mass of 1500 kg and they stick together. tkl38zzhd/umfe;5f; 9sm em j: ):vvlf 5.leaWhat is the speed of the cars after the collision?

A. 5.0 m/s

B. 10 m/s

C. 15 m/s

D. 20 m/s

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51#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A railroad freight car, mass 15,000 kg, iob) x,lo ,)fsss allowed to coast along a level track at a speed of 2.0 m/s. Itobfls))s ,,xo collides and couples with a 50,000-kg second car, initially at rest and with brakes released. What is the speed of the two cars after coupling?

A. 0.46 m/s

B. 0.60 m/s

C. 1.2 m/s

D. 1.8 m/s

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52#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A railroad car, of mass 200 kg, rollsaz1em cm(q qth: mi2-9ue 9sw9 with negligible friction on a horizontal track with a speed of 10 m/s. A 70-kg stunt man drotcq 2m:zw(9s-qa9mie u 9meh1ps straight down a distance of 4.0 m, and lands in the car. How fast will the car be moving after this happens?

A. 2.8 m/s

B. 4.7 m/s

C. 7.4 m/s

D. 10 m/s

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53#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 60-kg person walks on a 100-kg log at the rate of 0.80 m/s (with r.9(uec p(1 ycjm ymg5tespect to the log). Wyy e(p m5.(9c1mg tjucith what speed does the log move, with respect to the shore?

A. 0.24 m/s

B. 0.30 m/s

C. 0.48 m/s

D. 0.60 m/s

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54#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 4.0-N force acts for 3.0 s on an object. The force suddenly incdlv a,oi.m 7hf7yq ;3areases to 15 N and acts for one more second. What impulse was imparted by these forces ta. fdq;7,ah yivmo73l o the object?

A. $12 \; N \cdot s$

B. $15 \; N \cdot s$

C. $19 \; N \cdot s$

D. $27 \; N \cdot s$

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55#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A constant 9.0-N net force acts for 2.0 s onb6r, 9)kqo noy a 6.0-kg object. What is the object's change of velocity,qb9ny )ork6 o?

A. 3.0 m/s

B. 9.0 m/s

C. 27 m/s

D. 110 m/s

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56#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 2000-kg car, traveling to the right at 30 krtw ,8 ge*./ me:metxm/s, collides with a brick wall and comes to rest in 0.20 s. What is terew*, gkt8 m et./x:mhe average force the car exerts on the wall?

A. 12,000 N to the right

B. 300,000 N to the right

C. 60,000 N to the right

D. none of the above

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57#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 2.0-kg softball is pitched to yohf;q* iqkt + gq9 q)yfemk*/5fu at 20 m/s. You hit the ball back along the same path, and at the same speed. If the bat was in contact with the ball for 0.10 s, what is the magnitude of the average m*fq5/+kq y)t*ffqekq h ; 9giforce the bat exerted?

A. zero

B. $40 \; N$

C. $400 \; N$

D. $800 \; N$

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58#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.10-kg ball is dropped onto a table top. The speeds of the balle emw 0n4p:w+0rdcnj)x6uu i3 right before and right after hitting the table top are 5.0 m/s a3+edrce4: )n 6 xp0w ni0muujwnd 4.0 m/s, respectively. If the collision between the ball and the table top lasts 0.15 s, what is the magnitude of the average force exerted on the ball by the table top?

A. $0.67 \; N$

B. $1.3 \; N$

C. $3.0 \; N$

D. $6.0 \; N$

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59#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A machine gun, of mass 35.0 kr t+o;331wg2 tyetdd ng, fires 50.0-gram bullets, with a muzzle velocity of 750 m/s, at the rate of 300 rounds per n 1gtwde+dto2 ;y3rt3minute. What is the average force exerted on the machine gun mount?

A. $94.0 \; N$

B. $188 \; N$

C. $219 \; N$

D. $438 \; N$

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60#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A fire hose is turned on the door of a burning building85(nx;zb hpl: ztv xtn onz001f;djo+ in order to knock the door down. This requires a force of 1000 N. If the hose delivers 40 k tf(+;zx xbvd: ol jtp5on0hnz0n1z8;g per second, what is the minimum velocity of the stream needed, assuming the water doesn't bounce back?

A. 15 m/s

B. 20 m/s

C. 25 m/s

D. 30 m/s

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61#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Water runs out of a horizontal xzgnje(7ufw9 brut/(k : a,zj4 n )u/mdrainpipe at the rate of 120 kg per minute. It falls 3.20 m to the ground. Assuming the water doesn't splash up, what average force does(fk,(j9 n a4ujmezwbnux:/r/ uz7g ) t it exert on the ground?

A. $6.20 \; N$

B. $12.0 \; N$

C. $15.8 \; N$

D. $19.6 \; N$

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62#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A toy rocket, of mass 0.13 xw5 2dn3ihvp4:3tr;aq c qgv2 kg, achieves a velocity of 40 m/s after 3.0 s, when fire5v3tg wqrhc 4a:x;33pvd q 2ind straight up. What average thrust force does the rocket engine exert?

A. $1.2 \; N$

B. $1.6 \; N$

C. $2.8 \; N$

D. $4.4 \; N$

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63#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Two astronauts, of masses 60 kg and 80 kg, are initially at restg.uhx1lil lu7r .by78 in outer space. They push each other apart.18 xlylgub.riul7 h. 7 What is their separation after the lighter astronaut has moved 12 m?

A. $15 \; m$

B. $18 \; m$

C. $21 \; m$

D. $24 \; m$

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64#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 3.0-kg object moves to the right with a speed of 2.0 m/s. Irf- bi6;dy lp(w)fc+n+r box umo,t+(t collides in a perfectly elastic collisionu,lbx;rd+co) ffm(+b( it6+no-yp w r with a 6.0-kg object moving to the left at 1.0 m/s. What is the total kinetic energy after the collision?

A. $9.0 \; J$

B. $6.0 \; J$

C. $3.0 \; J$

D. $0 \; J$

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65#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.10-kg object with a 4mdasq do//4d velocity of 0.20 m/s in the +x direction makes a head-on elastic collision with a 0.15 kg object initially at rest. What is the final velocity of the 0.10-kg/sq44 /mo dadd object after collision?

A. -0.16 m/s

B. +0.16 m/s

C. -0.040 m/s

D. +0.040 m/s

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66#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10.0-g bullet moviu9ig kuwhlzkr*/h( p 9,s e;0rng at 300 m/s is fired into a 1.00-kg block at rest. The bullet emerges (the bullet does not get embedded in the block) with half of its original speed. What is 0eg*uks 99 rp/;hh,l( rzwki uthe velocity of the block right after the collision?

A. 1.50 m/s

B. 2.97 m/s

C. 3.00 m/s

D. 273 m/s

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67#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A proton, of mass m, at rest, is struck head-on by fkx,hmx06x u jxfn15l au( h)zl)v3(02bf csaan alpha-particle (which consists of 2 protons and 2 neutrons) moving at speed v. If the collision is completely elastic, what speed will the alpha-particle have a ,xn uj3lxc6l0x)ufxzksf 5ba)1f0( mv(2hha fter the collision? (Assume the neutron's mass equals the proton's mass.)

A. zero

B. 2v/3

C. 3v/5

D. 5v/3

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68#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 50-gram ball moving +10 m/s collides hea c0b .(a)b5te5y vrrwh nbq84,urp.e sd-on with a stationary ball of mass 100 g. The collision is elastic. eye 4 )wtbv0,5 sur8a(pr5.b cqnrbh. What is the speed of each ball immediately after the collision?

A. -3.3 m/s and +6.7 m/s

B. +3.3 m/s and -6.7 m/s

C. -6.7 m/s and +3.3 m/s

D. +6.7 m/s and -3.3 m/s

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69#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

A ball of mass 400 g moving toward the east wi(. ( fiuppcjud /r4.uith a speed of 3.70 m/s collides head-oncrjpu. i (p4u./if(du with a 200 g ball sitting at rest. The collision is perfectly elastic.
(a) Determine the velocity of the first ball after the collision.
(b) Determine the velocity of the second ball after the collision.
(c) Is kinetic energy conserved in this collision?

该题自我估分: (必填) (满分:1.0分)

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70#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 2.0-kg mass moves with a speed of 5.0 m/s.g (z4g (y8i mlqthfy(ol192qd It collides head-on with a 3.0 kg mass at rest. If the collision is perfectly inelastic, what is the speed of (4(2zyylmgoi 1 tgf(hd8qlq 9the masses after the collision?

A. 10 m/s

B. 2.5 m/s

C. 2.0 m/s

D. 0, since the collision is inelastic

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71#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 2.0-kg mass moving to the east at a sksd 0 :8dbr,pt8y7wrr t z y):96quvwapeed of 4.0 m/s collides head-on in a perfectly inelastic collision with a stationary 2.0-kg mass. How much kinetic energy is lost during this collisir6drs:qp)0tbr9 ,k8:yy8 dwa 7 uzwtvon?

A. $16 \; J$

B. $4.0 \; J$

C. $8.0 \; J$

D. zero

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72#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A car of mass m, traveling with a velocity v, sfc fl3)ug:h-gc :6 wrxtrikes a parked station wagon, who's mauc3 :- glrc)fw6:xghfss is 2m. The bumpers lock together in this head-on inelastic collision. What fraction of the initial kinetic energy is lost in this collision?

A. 1/2

B. 1/3

C. 1/4

D. 2/3

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73#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

A 15-g bullet traveling 213 m/s in a verticaloo 3f+y/ ijmvw: js 61x:5utcqohj11q direction buries itself in a 2.4-kgc 1i6yj qm3o /1uho t1 5qo:j+xvwjf:s block of wood a rest directly above it. As a result, the bullet/block combination moves vertically upward.
(a) Determine the velocity of the bullet/block combination at the point of impact.
(b) Determine the maximum height reached by the bullet/block combination.
(c) Is kinetic energy conserved in this collision?

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74#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car traveling at 90.0 km/h east collides with a 3000-kg car travelingvt.1w h+z. fksq6uo/m at 60.0 km/h south. The two cars stick together after the collio.q hs6t .v/f +wu1kmzsion. (See Fig. 7-1.) What is the speed of the cars after collision?

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A. 8.33 m/s

B. 13.9 m/s

C. 17.4 m/s

D. 21.7 m/s

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75#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car traveling at 90.0 km/h east collides with a 3000-kg carq1k at 53)6r3dddhws t traveling at 60.0 km/h south. d )q3dts56rak twd1h3The two cars stick together after the collision. (See Fig. 7-1.) What is the direction of motion of the cars after collision?

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A. $36.9^{\circ}$ S of E

B. $36.9^{\circ}$ E of S

C. $53.1^{\circ}$ S of E

D. $53.1^{\circ}$ E of S

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76#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Two objects move on a level frictionless su(m(m 3*lky djxs(d/ blrface. Object A moves east with a momentum of 24 kgm/s. Object B moves north with momentum 10 kg* y3x/(lmdb(jdmslk( m/s. They make a perfectly inelastic collision. What is the magnitude of their combined momentum after the collision?

A. 14 kgm/s

B. 26 kgm/s

C. 34 kgm/s

D. cannot be determined without knowing masses and velocities

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77#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A small bomb, of mass 10 kg, is moving toward thfg.-r xml 4yi15w v5pfe North with a velocity of 4.0 m/s. It explodes into three fragments: a 5.0-kg fragment moving west with a speed of 8.0 m/s; a 4.0-kg fragment moving east with a speed of 10 m/s; and a third fragment with a mass of 1.0 kg. What is the velocity of the third fragment? (Neglect aliw p .5-1m5 yfvfx4rgir friction.)

A. zero

B. 40 m/s north

C. 40 m/s south

D. none of the above

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78#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 4.00-kg mass sits at thepw/k(,csu1 ju j,9 jqt origin, and a 10.0-kg mass sits at x = + 21.0 m. Where is the center of mass on the x-ax(ujscq,jk 9jp1tuw /,is?

A. +7.00 m

B. +10.5 m

C. +14.0 m

D. +15.0 m

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79#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The center of mass of a two-particle system is at the originl7 wjbt 7ag3 bg6+ui;d. One particle is located at (3.0 m, 0) and has a mass of 2.0 kg. gbdig;t7a+ bl 637wu jWhat is the location of the second mass of 3.0 kg?

A. (-3.0 m, 0)

B. (-2.0 m, 0)

C. (2.0 m, 0)

D. (3.0 m, 0)

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80#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Three masses are positioned as follows: 2.0 kg at (0, 0), 2.0 k 5v0 giy zd05(txfhmd4g at (2.0, 0), and 4.0 kg at (2.0, 1.0). Dete5dgx0(zy t5v4f0idm hrmine the coordinates of the center of mass.

A. (0.50, 1.5)

B. (1.5, 0.50)

C. (2.5, 1.5)

D. (2.5, 0.50)

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81#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Three masses, 1.0 kg, 2.0 kg, and 3.0 kg, are located at (0, 0), (1.0 mz+2 h1a1njv do, 1.0 m), and (2.0 m, a1dh1o +n2jvz -2.0 m), respectively. What is the location of the center of mass of the system?

A. (1.3 m, 0.67 m)

B. (1.3 m, -0.67 m)

C. (-1.3 m, 0.67 m)

D. (-1.3 m, -0.67 m)

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82#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 3.0-kg mass is positioned at (0, 8.0), and a 1.0-yexs6))j c-ah kg mass is positioned at (12, 0). What are the coordinates of a 4.0-kg mass which will result in the center of mass o y ae-j)6sc)xhf the system of three masses being located at the origin, (0, 0)?

A. (-3.0, -6.0)

B. (-12, -8.0)

C. (3.0, 6.0)

D. (-6.0, -3.0)

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83#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Use Table 7-1 to calculate the position of the yi8 *rhjcu* 2p:qg7ulCM of a whole leg including the foot when the leg is sty :8ugp7ch*qi*2r ujl retched straight out. Assume the person is 1.60 m tall.

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A. 0.20 m above the bottom of the foot

B. 0.32 m above the bottom of the foot

C. 0.51 m above the bottom of the foot

D. 0.54 m above the bottom of the foot

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