Question

兩個(gè)共點(diǎn)力同向時(shí)合力為a，反向時(shí)合力為b，當(dāng)兩個(gè)力垂直時(shí)合力大小為（    ）

A.        B.          C.         D.

Answer 1

解析：假設(shè)兩個(gè)力分別為F₁、F₂，則：

同向時(shí)：F₁+F₂=a                                                        ①

反向時(shí)：F₁-F₂=b                                                        ②

當(dāng)兩力垂直時(shí)：F=                                                                  ③

由①②得：F₁=(a+b)/2，F(xiàn)₂= (a-b)/2

代入③得：F=

答案：B