题目

 做匀变速直线运动的物体，某时刻的速度大小是8m／s，ls后的速度大小变为4m／s，则此物体在这1s内通过的位移   （    ）A. 等于6m           B. 小于6mC. 大于6m            D.可能等于2m  答案： D   21、Most of us know we should cut down on fat, but knowing such things isn’t much help when it        _____shopping and eating． A．refers to            B．speaks of              C．focuses on        D．comes to