杠杆尺及支架

科学启示：

Archimedes once said：“Give me a fulcrum，I can lift the earth。”In real life，Although no one can move the Earth，But with this fulcrum，But it can move a lot of heavy things。Let's see how the lever saves effort through the following experiment。 

Scientific production：

1，Get to know experimental equipment：Little Butterfly, Little Axis、Weights、Nut、小Weights、Fine copper wire、Plastic wire、Balance ruler、"Hook"、Vehicle body、Base、Large column。   

2，Install the large column on the base，Let's turn the sky over again、平尺装在Large column上，One lever assembly is completed。   

3，把不同数量的Weights分别挂在Balance ruler的不同位置，Observe and record the state of the lever，What pattern have you discovered?     

4，用三根Plastic wire头分别穿过小碟上的三个小孔挂住小蝶，（Fold the copper wire in half and cut it short）分别用铜丝把"Hook"和三根Plastic wire保持Equal的距离扎接，挂在Balance两端的小孔内，Use smallOBalance the rim。   

5，Place small heavy objects and weights respectively into the small butterflies at both ends of the balance，保持Balance平衡。再把不同Weight的小重物和不同数量的Weights放入两侧小蝶内，Balance the balance，Think about it. What principle does balance illustrate？In the experiment, we found that,如果被测小重物的Weight和Balance的Weight不EqualBalance就会倾斜Balance平衡说明Weights的Weight和被测小重物的WeightEqual。

Hint：实验的时候不同的Weights分别挂在Balance的不同位置上,It was made under the correct guidance of the teacher。

Knowledge expansion：

    The lever principle is also known as“Leverage balance condition”。To balance the leverage，Two forces acting on a lever（Apply more force、Fulcrum and resistance point）Their size is inversely proportional to their lever arms。"Power"×Power arm=Resistance×Resistance arm，Expressed in an algebraic expression asF1·l1=F2·l2。In the formula，F1Express motivation，l1表示Power arm，F2Indicate resistance，l2表示Resistance arm。从上式可看出，To balance the leverage，Power arm是Resistance arm的几倍，Power is a fraction of resistance。    

Balance：A weighing instrument。From the fulcrum(shaft)在梁的中心支着Balance梁而形成两个臂，There is a plate hanging on each arm，One of the plates contains an object of known weight，Place the object to be weighed in another plate，The deflection of the pointer fixed on the beam when it does not swing and points to the center scale indicates the weight of the object to be weighed。Balance是实验室中常用的仪器。Balance是A weighing instrument,It is an instrument for measuring the mass of an object。It is made based on the principle of leverage，There is a small pan at each end of the lever，Place a weight at one end，Place the object to be weighed at the other end，A pointer is installed in the center of the lever，When both ends are balanced,The mass at both ends（Weight）Equal。These truths have long been common sense to those who have studied physics，Modern balance，More and more precise，More and more sensitive，The types are also increasing。We all know，有普通Balance、分析Balance,There is a constant analytical balance、Microanalytical balance、半Microanalytical balance等等 。

Scientific inquiry：

1，Observe carefully，Think about which applications of the lever principle are in life？Illustrate with examples。

2，What is leverage?

3，了解Balance和杠杆的关系 Experimental key points：

4，The conditions and laws of leverage balance。