大物思考题（Big things）.docVIP

大物思考题（Big things） Answer Mechanical and thermal electromagnetics optics Modern physics 1. if the time can be measured as a swing cycle value? Why? A: no.. Because of a large random error measurement, multiple measurements can reduce random error. 2. a radius of less than under the radius of disk disk in disk, and the center line, the discussion of three line pendulum cycle and no-load cycle is compared to the increase and the decrease or not? Explain the reason. Answer: quality when two disks for uniform distribution, compared with no-load, swing cycle will be reduced. Because if the two disc as a radius equal to the original lower disc, the disc inertia is less than I0 quality equal to that of the same diameter, according to formula (3-1-5), T0 will reduce the swing period. 3. three line pendulum by air damping in the swing amplitude, more and more small, whether it will change the cycle? Great influence on the measurement result? Why? Answer: the decreasing cycle has little influence on the measurement results, because the measurement time is short. 2 measurement of elastic modulus of metal wires 1. what are the advantages of optical lever, how to improve the sensitivity of the optical lever measurement? A: the advantage is that it can measure the small length variation. To improve the vertical distance magnification is increasing the scale distance of D or properly reduce the optical lever before and after the foot of B, can improve the sensitivity, because the magnification of the optical lever is 2D/b. The 2. is how to judge the disparity, and eliminate the disparity? Answer: eyes at the eyepiece to move up and down, if the scale level telescope crosshair scale and relative displacement, this phenomenon is called parallax, fine focusing handwheel can eliminate parallax. The 3. why by experimental data processing method? Answer: the difference method is a basic method of experimental data processing, the essence is to make full use of the data from the experimen