2021-05-22匀速圆周运动 的运动方向改变幅度不变，为什么描述方向变化的法向加速度不是0

正确理解法向加速度

in our common conigtion,

we think acceleration describes the rate  of speed change  (速度改变的快慢）.

After learning Theoretical Machanics(理论力学), we konw that in circular motion ,there are two kinds of accerelation.

The tangent（切向） accerelation and the normal（法向） acceleration.The latter

one describes the change degree in a unit of time of  the motion direction as the textbook says,

but ... in the situation of uniform circular motion(匀速圆周运动),we will easily think that as the direction change 

range(方向变化幅度)

every second is same ,  the thought that its normal acceleration value should be zero comes to our mind .

In fact, we should make comparision at this time ,to conventional (传统的) tangent accrelation ,if speed change exists,

its accrelation value is not zero .In the same way ,if direction change exists , the normal accerelation value also is not zero.

Therefore, we should consolidate our conigtion to accrelation : it describes the change amount of speed or direction in a unit of

time, not the change of changing amount .

 

有些同学觉得匀速圆周运动里，方向的变化幅度是相同的，那描述方向变化的法向加速度（或者在这里叫向心加速度）应该是0

其实这这没有理解好加速度的含义：它描述的就是某种东西的改变，只要改变存在，加速度就存在。