V to lengthen or extend (a speech, etc); prolong in time 延长
Protracting object's free-body diagram is a course of analysising object's force from other object.
画受力图是解决力学问题关键的一步。
The essentiality of protracting curve was known.
绘制曲线的重要性是众所周知的。
Protracting object's free-body diagram is a course of analysising object's force from other object in fact.
绘制物体受力图的过程就是对物体进行受力分析的过程，学会画受力图是解决力学问题关键的一步。
应用推荐