- An attempt on guidance in the study of balance of the moment of force and rotation of windmill using the newly designed tools and through theoretical results -

Abstract

Many kind of rotatable tools such as windmill, lever, beam balance and axle are adopted for teaching tools in the elementary school in Japan. Children study the condition of balance on lever, beam balance and axel, and observe the rotation of windmill and axel. According to the authors' investigation on children's understanding about these phenomena, they could answer correctly to the questions concerning to balance of levers and balances with straight beam but they could not for 'yajirobee' , one of balances with bended arms. It is clear from these results that children have the conception of moment arm to a slight degree. To make better such a situation, the authors designed new tools on which the moment arm can easily be find and be measured for any balances with complicatedly bended arms. Through the guidance of the conception of moment arm using newly designed tools, children's understandings on the balance of forces became very much better. As the balance of forces and the rotation of objects can be understood under the common physical concept viz. moments of forcesin or not in equilibrium, the authors gave simple theoretical results for the rotation of windmill and shew how the shape of wing and length of arm affect on the angular velocity and on the wind up power of the windmill and also shew how moment of wind pressure acts on the windmill. A device is also made to measure the angular velocity of windmill. The experiment al results using this device shew good agreement with theoretical results. The guidance of windmill using this device also produced good results.