一題很奇怪力學

一題很奇怪力學 A 15-kg block B is suspended from a 2.5-m cord attached to a 20-kg cart A.Neglecting friction, determine the tension in the cord,immediately after
the system is released from rest in the position shown.

他的圖就是A用繩索吊一個15公斤的B,然後在斜坡(與水平夾25度)朝右下角滑落

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請問為什麼B的等效力圖沒有受2.5w^2(朝上)

B不是應該要有向心加速度嗎