Question

某同学用如图所示的实验装置来验证“力的平行四边形定则”．弹簧测力计A挂于固定点P，下端用细线挂一重物M．弹簧测力计B的一端用细线系于O点，手持另一端向左拉，使结点O静止在某位置．分别读出弹簧测力计A和B的示数，并在贴于竖直木板的白纸上记录O点的位置和拉线的方向．                                                      

（1）本实验用的弹簧测力计示数的单位为N，图中A的示数为              N．                   

（2）下列不必要的实验要求是                                                               ．（请填写选项前对应的字母）          

A．应测量重物M所受的重力                                                                                         

B．弹簧测力计应在使用前校零                                                                                        

C．拉线方向应与木板平面平行                                                                                       

D．改变拉力，进行多次实验，每次都要使O点静止在同一位置                                      

（3）某次实验中（情景如图），该同学发现弹簧测力计B的示数太小，请在保持OP方向不变的前提下，为解决该问题提一个建议．                                                                                                                         

                                                                                        

                                                                                                                                       

Answer 1

（1）3.60； （2）D；（3）增大M的质量．