问题
选择题
某物体沿一直线运动，其v-t图象如图所示，则下列说法中不正确的是（ ）
A．第2s内和第3s内速度方向相反
B．第2s内和第3s内的加速度方向相反
C．第3s内速度方向与加速度方向相反
D．第5s内速度方向与加速度方向相反
答案
A、第2s内和第3s内速度均为正值，速度方向均为正方向，方向相同．故A错误．
B、第2s内物体做加速运动时，速度与加速度方向相同；第3s内物体做减速运动时，速度与加速度方向相反．而第2s内和第3s内速度方向相同，则第2s内和第3s内的加速度方向相反．故B正确．
C、第3s内物体做减速运动时，速度与加速度方向相反．故C正确．
D、第5s内物体做减速运动时，速度与加速度方向相反．故D正确．
本题选错误的，故选A
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