在“探究弹力和弹簧伸长量的关系，并测定弹簧的劲度系数”的实验中，实验装置如图所示．所挂钩码的重力相当于对弹簧提供了向右的恒定拉力．实验时先测出不挂钩码时弹簧的自然长度，再将5个钩码逐个挂在绳子的下端，每次测出相应的弹簧总长度．
(1)有一个同学通过以上实验测量后把6组数据描点在坐标系图中，请作出F－L图线．
(2)由此图线可得出该弹簧的原长L0=________ cm，在弹性限度内的劲度系数k=________ N/m.
(3)试根据该同学以上的实验情况，帮助他设计一个记录实验数据的表格(不必填写其实验测得的具体数据)．
(4)该同学实验时，把弹簧水平放置与弹簧悬挂放置相比较，
优点在于：________________________________________________________________
缺点在于：________________________________________________________________
(1) F－L图线如图所示：（最后一个点连线也可以）········································· (2分)
(2) L0＝5 cm········································································································· (2分)
k＝20 N/m···································································································· (2分)
(3) 记录数据的表格如上表················································································· (2分)
(4) 优点是：可以避免弹簧自身重力对实验的影响．······································· (1分)
缺点是：弹簧与桌面及绳子与滑轮间存在的摩擦会造成实验误差············ (1分)