如图( a ),物块和木板叠放在实验台上,物块用一不可伸长的细绳与固定在实验台上的力传感器相连,细绳水平。 t = 0 时,木板开始受到水平外力 F 的作用,在 t = 4s 时撤去外力。细绳对物块的拉力 f 随时间 t 变化的关系如图( b )所示,木板的速度 v 与时间 t 的关系如图( c )所示。木板与实验台之间的摩擦可以忽略。重力加速度取 10m/s 2 .由题给数据可以得出( )
【单选题】听力原文:WA Sam, when is this week's production meeting? MA It's at ten o'clock in the Green Willow Room on the second floor. The same place as last week. WA Right, but last week it was at eleven o'clock ...