题干

如图所示,小车上物体的质量m=8kg,它被一根在水平方向上拉伸了的轻弹簧拉住而静止在小车上,这时弹簧的弹力是6N.现对小车施一水平向右的作用力,使小车由静止开始运动,在小车的加速度由零逐渐增大到1m/s2的过程中,以下说法正确的是(  )

A:物体与小车始终保持相对静止,弹簧对物体的作用力逐渐变大

B:物体受到的摩擦力先减小、后增大,先向左、后向右

C:当小车的加速度为0.75m/s2时物体不受摩擦力的作用

D:小车以1m/s2的加速度向右做匀加速直线运动时物体受到的摩擦力为8N

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答案(点此获取答案解析)

B,C

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