4-8a前4s内的位移为:x=2at22a(-4)2又由X1:X2=3:2联立解得:t=5s.故C正确,ABD错误。故本题正确答案为:C。 结果一 题目 汽车刹车后做匀减速直线运动,已知汽车前4秒的位移与最后4秒的位移之比为3.2,则汽车停下来用了()A.10sB.8sC.5sD.4.25s 答案 把汽车的运动视为反向初速度为0的匀加速直...
( )A.eatingB.eatC.is eating8.It's ___ cat. The cat is ___. ( )A.her; hersB.hers; herC.her; her9.___ birthday is in March. ( )A.Amy's motherB.John's father'sC.Amy mother's10.Keep ___ the right, please. ( )A.atB.onC.to11.Th...