一石块做自由落体运动，到达地面．把它在空中运动的时间分为相等的三段，如果它在第一段时间内的位移是1.5m，那么它在第三段时间内的位移是（）
A.13.5m
B.1.5m
C.7.5m
D.4.5m
参考答案：C
解析：从静止开始的匀变速直线运动，连续相等的时间间隔内位移之比为1：3：5，因此若第一段为1.5m，则第三段为5×1.5="7.5"m，C正确
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| I'm __1__ you from the Hilltop School Skating Marathon. Here, students are skating to raise money for charity. For every hour they __2__, each student raises ten yuan for charity. The skating marathon has been going for five hours now, and several skaters are __3__ skating. Alison was the first one to __4__ and has been skating for the whole five hours. Next is Sam, and he has been skating for four hours. Lu Ning has been skating for four hours too, and Li Chen __5__ started an hour ago. |