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“轉動”這個課题從教學法方面來說是最困難的課题之一。困難首先在於作匀速圓周運動的質點的向心加速度的論證。教師一般是用下列的方案來講述這個問題的: (1) 速度是一個矢量,因此只有在它的大小和方向都不改变的情形下才是一個定值。例如,在匀速直线運動中速度就是一個定值。 (2) 在質點的匀速圓周運動中,速度只是大小保持一定,方向則在不断变化着,因此,匀速圓周運動是一個变速運動。 (3) 任何變速的運動,都是有加速度的運動,這就是說,質點的匀速圆周運動是有加速度的運動。 (4) 質點在匀速圓周運動中的加速度在任何時刻都是指向圆心並可用下述公式來計算:
The issue of “turning” is one of the most difficult topics in pedagogy. The difficulty lies, first and foremost, in the centripetal acceleration of particles moving at uniform circular motion. Teachers generally use the following program to tell the story: (1) speed is a vector, so it is only a fixed value in the case of its size and direction are not changed. For example, in a uniform linear motion speed is a constant value. (2) In constant circular motions of particles, the speed is only constant while the direction is constantly changing. Therefore, the uniform circular motion is a variable speed motion. (3) Any motion of variable speed, is a movement of acceleration, that is to say, the constant circular motion of the particle is the acceleration of the movement. (4) The accelerations of particles in constant circular motion point to the circle center at any time and can be calculated by the following formula: