if there is no friction what happens to the speed of a ball rolling on a horiontal surface?

问题描述:

if there is no friction what happens to the speed of a ball rolling on a horiontal surface?

你那个单词应该是打错了,是horizontal,是“水平的”的意思.
整个题目意思:如果没有摩擦力,在水平面上运动的小球会怎样?
答案是:会按其原有速度做匀速直线运动.