Question

某同學(xué)用如圖所示的實驗裝置來驗證“力的平行四邊形定則”．彈簧測力計A掛于固定點P，下端用細(xì)線掛一重物M．彈簧測力計B的一端用細(xì)線系于O點，手持另一端向左拉，使結(jié)點O靜止在某位置．分別讀出彈簧測力計A和B的示數(shù)，并在貼于豎直木板的白紙上記錄O點的位置和拉線的方向．                                                      

（1）本實驗用的彈簧測力計示數(shù)的單位為N，圖中A的示數(shù)為              N．                   

（2）下列不必要的實驗要求是                                                               ．（請?zhí)顚戇x項前對應(yīng)的字母）          

A．應(yīng)測量重物M所受的重力                                                                                         

B．彈簧測力計應(yīng)在使用前校零                                                                                        

C．拉線方向應(yīng)與木板平面平行                                                                                       

D．改變拉力，進(jìn)行多次實驗，每次都要使O點靜止在同一位置                                      

（3）某次實驗中（情景如圖），該同學(xué)發(fā)現(xiàn)彈簧測力計B的示數(shù)太小，請在保持OP方向不變的前提下，為解決該問題提一個建議．                                                                                                                         

                                                                                        

                                                                                                                                       

Answer 1

（1）3.60； （2）D；（3）增大M的質(zhì)量．