物理03-04二学期末

浙江大学浙江大学 2003-2004 学年第二学期期末考学年第二学期期末考试试 Physics（） 课程试卷 开课学院 理学院 任课教师 考试时间 120 分钟 姓名 专业 学号 组号_ 题序 选择 题 一二三四五六七八总分 得 分 评卷 人 Molar gas constant R=8.31Jmol-1K-1 Boltzmann constant k=1.3810-23JK-1 Speed of light in a vacuum c=3.00108m/s . Multiple choices (there is one correct answer only): 1. The center of mass a system of particles has a constant velocity if: A. the forces exerted by the particles on each other sum to zero. B. the external forces acting on particles of the system sum to zero. C. the velocity of the center of mass is initially zero. D. the particles are distributed symmetrically around the center of mass. E. the center of mass is at the geometric center of the system . 2. A wheel starts from rest and has an angular acceleration that is given by (t)=6t2, where t is in seconds and is in radians per second-squared. The time it takes to make 10 rev（转） is: A. 2.8s B. 3.3s C. 4.0s D. 4.7s E. 5.3s 3. A spool(线轴) of wire rests on a horizontal surface as in Figure. As the wire is pulled, the spool does not slip at the contact point P. On separate trials, each one of the forces F1, F2, F3, and F4 is applied to the spool. Among these 4 forces, which one can make the spool roll in clockwise? (Note that the line of action of F2 passes through P.) P A. F1 B.F2 C.F3 D. F4 E.none of the above 4. A pulley with radius R and rotational inertia I is free to rotate on a horizontal fixed axis through its center. A string passes over the pulley. Mass m1 is attached to one end and mass m2 is attached to the other. At one time m1 is moving downward with speed v. If the string does not slip on the pulley, the magnitude of the total angular momentum, about the pulley center, of the masses and pulley, considered as a system, is given by: A. (m1- m2)vR+Iv/R B.(m1+ m2)vR+Iv/R C.(m1- m2)vR-Iv/R D. (m1+ m2)vR-Iv/R E.none of the above 5. An ideal spring, with a pointer attached to its end, hangs next to a scale. With a 100-N weight attached and at rest, the pointer indicates “40” on the scale as shown. Using a 200-N weight instead results in “60” on the scale. Using an unknown weight X instead results in “30” on the scale. The weight of X is: A.10N B.20N C.30N D.40N E.50N 6. The potential energy for a body of mass m that is acted on by a very massive body is given by U=-mgx+kx2/2. The corresponding force is: A.mgx2/2+kx3/6. B.mgx2/2-kx3/6. C.mg+kx/2 D.mg+kx E.mg-kx 3 ( of 7 pages) 7. Two particles, each of mass m, are a distance d apart. To bring a third particle, also with mass m, from far away to the point midway between the two particles an external force does work given by: A. 4Gm2/d B. -4Gm2/d C. 4Gm2/d2 D. -4Gm2/d2 E. none of above 8. The displacement of a string carrying a traveling sinusoidal wave is given by y(x,t)=ymsin(kx-t-). At time t=0, the point at x=0 has a velocity of zero and a positive displacement. The phase constant is: A. 45 B. 90 C. 135 D. 180 E. 270 9. Two sinusoidal waves travel in the same direction and have the same frequency. Their amplitudes are y1m and y2m. The smallest possible amplitude of the resultant wave is: A. y1m+ y2m and occurs when they are 180out of phase B. y1m- y2mand occurs when they are 180out of phase C. y1m+ y2m and occurs when they are in phase D. y1m- y2mand occurs when they are in phase E. y1m- y2mand occurs when they are 90out of phase 10. Two sources, S1 and S2, each emit waves of wavelength in the same medium. The phase difference between the two waves, at the point P shown, is (2/)(r2-r1)+. The quantity is: A. the distance S1S2 B. the angle S1PS2 C. /2 D. the phase difference between the two sources E. zero for transverse waves, for longitudinal waves .Calculation problems (present the necessary equations in solution): 1、A bullet of mass m moving with velocity strikes and becomes embedded at the v edge of a cylinder of mass M and radius R0, as shown in Fig. The cylinder, initially at rest, begins to rotate about its symmetry axis, which remains fixed in position. Assuming no frictional torque, what is the angular velocity of the cylinder after this collision? Is kinetic energy conserved? 2、As shown in Fig., a simple harmonic wave is traveling along tkxAysin the positive direction of X axis, the reflected point P is a node and and 4/3OP . Find: (1) the oscillation equation 6/DP at position P caused by incidence wave; (2) the reflected wave equation; (3) the standing wave equation; (4) the resultant oscillation equation at position D. 5 ( of 7 pages) 3、How much work must be done to increase the speed of a particle with rest mass from rest to ( where is the speed of light in vacuum)? 0 mc8 . 0c 4、 An observer A is at rest in the frame OXY while another observer B moves along the X-axis with a constant velocity 0.8c (c is the light speed in vacuum). In frame OXY the observer A find that the area enclosed by a geometric circle is 12 cm2. Relying on the relativistic effect of length contraction, this geometric figure becomes an ellipse for Observer B. What area is the ellipse enclosed measured by B? (It is known that the area of an ellipse with semimajor axis a （长半轴）and semiminor axis b （短半轴）can be calculated by Sab). 5、Figure shows a hypothetical speed distribution of N molecules in an ideal gas, with for and for . Find 2 d d )(Cv v N vN 0 0vv 0)(vN 0 vv (1) an expression for C in terms of N and ? 0 v (2) the average speed of the particles: (3) the rms speed of the particles? 6、A power plant generates 640 MW of electric power. It has an efficiency of 38% . At what rate does it dissipate heat? If a river carries the waste heat away, and environmental concerns limit the temperature rise of the water to 3oC, what mass flow rate(流量) is required in the river? (the specific heat capacity of water c=4200J/kgK) 7 ( of 7 pages) 7、One mole of a monatomic ideal gas initially at , is heated and expands at 0 p 0 V constant pressure to a volume 4V0. It is then cooled at constant volume until the pressure has dropped to 0.5. Calculate 0 p