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,F₂= (A-b)/2?

       代入③得：F=.?

答案：B