story suddenly all became clear to me.It was about a blind person,Louis Braille.He lived in a time when the blind couldn't get much education.But Louis didn't give up.Instead,he invented a reading system of raised dots(点),which opened up a whole new world of knowledge to the blind...
在直线运动,若物体运动的速度随时间均匀变化,则物体做匀变速直线运动.做匀变速直线运动的物体加速度不随时间改变;做匀速直线运动的物体的加速度为零W. 判断物体做加速运动还是减速运动的方法 从加速度与速度的方向关系可判断物体是加速还是减速:①当加速度与速度的方向相同时,不管加速度的大小是否变化,物体都是做加速...