论文部分内容阅读
近年高考试题中,多次出现多过程的周期性运动问题.对于这一类问题,不一定要用图象法求解,但利用图象法解题,形象、直观,思路清晰,可达到化难为易之目的.现举数例作分析.一、应用速度-时间图象解题速度图象的物理意义:(1)反映了v、t的对应关系,图线上的每一个点表示物体在某时刻的速度.(2)图线的斜率表示物体的加速度.(3)图线与ot轴所围成的面积表示物体的位移,当面积在ot轴上方时,表示位移为正值;当面积在ot轴下方时,表示位移为负值.速度图象不仅反映了速度随时间的变化情况,同时也反映了加速度、位移的变化情况.速度图象是分析解决复杂运动问题的一个有力工具.例1.(’88高考题)一物体放在光滑水平面上,初速度为零.先对物体施加一向东的恒力F_1,历时1秒钟;随即把此力改为向西,大小不变,历时1秒钟;接着又把此力改为向东,大小不变,历时1秒钟;如此反复,只改变力的方向,共历时1分钟.在此1分钟内.(A)物体时而向东运动,时而向西运动,在1分钟未静止于初始位置之东;(B)物体时而向东运动,时而向西运动,1分钟未静止于初始位置;(C)物体时而向东运动,时而向西运动,1分钟来继续向东运动;(D)物体一直向东运动,从不向西运动,在1分钟未静止于初始位置之东.
In recent high-achieving exams, multiple periodical motion problems have appeared many times. For this type of problem, it is not necessary to use the image method to solve the problem. However, using the image method to solve problems, the image is intuitive, the thinking is clear, and the difficulty can be achieved. The purpose of Yi. Now take a few examples for analysis. First, the application of speed-time image problem speed physical meaning of the image: (1) reflects the corresponding relationship between v, t, each point on the graph line represents the object in The speed at a certain moment. (2) The slope of the graph represents the acceleration of the object. (3) The area enclosed by the graph and the ot axis represents the displacement of the object. When the area is above the ot axis, it means that the displacement is positive; When the area is below the ot axis, it means that the displacement is negative. The velocity image not only reflects the change of velocity with time, but also reflects the change of acceleration and displacement. The velocity image is a powerful tool for analyzing and solving complex motion problems. Example 1. (’88 College Entrance Examination Question) An object is placed on a smooth horizontal surface with an initial velocity of zero. A constant east force F_1 is applied to the object for 1 second; this force is then changed to westward, and the size is not Change, which lasted 1 second; then it changed the force eastward, the size remained unchanged, and it lasted 1 second; for example, This repetition only changes the direction of the force and lasts 1 minute. Within this 1 minute. (A) The object moves eastward, sometimes west, and does not rest in the east of the initial position in 1 minute; (B) The object is Moving eastwards, sometimes moving westwards, one minute is not still at the initial position; (C) The object moves eastwards, sometimes westwards, and one minute to continue eastwards; (D) The object moves eastward, never Move west, not in the east of the initial position in 1 minute.