裁纸刀是费力杠杆还是省力杠杆?

解题思路：（1）裁纸刀受到纸的压力，作用点在纸与刀的接触点，方向垂直接触面向上，据此画出裁纸刀受到纸的压力示意图；（2）力臂的画法：①首先根据杠杆的示意图，确定杠杆的支点．②确定力的作用点和力的方向，画出力的作用线．③从支点向力的作用线作垂线，支点到垂足的距离就是力臂．

（1）从纸与刀的接触点A垂直接触面向上画出裁纸刀受到纸的压力示意图，如图所示：
（2）画出动力作用线，从支点O作动力作用线的垂线，可得动力臂，如图所示：

点评：
本题考点： 力的示意图；力臂的画法．

考点点评： 画力的示意图要确定力的三要素；画力臂时，必须找准支点和力的作用线．

不知道我理解的是不是楼主想要的答案,刀片用一段时间用,刀尖通常会变钝,刀片上有一排斜纹,可沿此线将前端用钝的折断,新刀尖还是很利的.通常刀架尾部可拆下来,有个缝,帮助你折断刀片.

不能

过支点O作垂直于动力作用线的垂线段，可得动力臂L₁；过阻力臂L₂的左端，作垂直于阻力作用线的垂线段，可得阻力示意图．如图所示

The paper cutter is specially intended for the kids to cut paper . The fish shape can protect the hands of kids from being injured and it also looks very attractive . It is easy and safe for kids to use . Just press the button and the blade can touch the paper . You just need to move the fish body and you can cut the paper out . I am sure it is a reliable product that can be popular with the kids when used .

How to make Kongming Lamp
a.Use a paper knife to pare the bamboo strip into one that is under three milimeters in thickness. Then, bend it into a ring and secure the ends with cotton string or glue. The bamboo has flexibility so the bamboo ring may not be round. Use a small fire to make it softer and secure it when it's a perfect circle.
b. Use the sharp-tipped tong to take off the insulating tape from the wire to obtain the thin brass wires. But the brass wires can't be too thin, or it'd be broken when burned. Twist three brass wires into one to solve this problem.
c. Cut a thin piece of paper into a piece shown in the illustration. Glue the side of the first piece with the side of the second one, and then the third one, fourth one...until it becomes a sphere-like object with holes on each end and a diameter of about sixty centimeters. Then cut out a round shape of thin paper to cover the hole on top of the sphere. When the glue is dry, blow up the balloon, find a thin and narrow bamboo strip, bend it into a ring that's the size of the hole on the bottom of the sphere. Inside the ring, place two thin wires perpendicular to each other and tie them tight on the ring. Glue the ring on the side of the hole. The balloon can't leak air.
d. Tie the brass wires on the two side of the bamboo ring, then glue the chimney onto the ring. Tie some cotton onto the brass wire,damp it with alcohol, light it and let it go. The lamp can't be too small, or it would be hard to fly in the air.