When ____behind , the little girl always cries for Mum. A.leaving B. being left C. t leave D. left 答案:D
(1)如图所示,质量为m的物体用细绳OC悬挂在支架上的O点,轻杆OB可绕B点转动,求细绳OA中张力T大小和轻杆OB受力N大小.
(2)如图所示,水平横梁一端A插在墙壁内,另一端装有小滑轮B,一轻绳一端C固定于墙壁上,另一端跨过滑轮后悬挂一质量为m=10 kg的重物,∠CBA=30°,则滑轮受到绳子作用力为________.
A.50 N
B.50N
C.100 N
D.100N