Question

光滑平面上一運(yùn)動(dòng)質(zhì)點(diǎn)以速度v₀通過點(diǎn)O,如圖5-1-6所示.與此同時(shí),給質(zhì)點(diǎn)加上沿x軸正向的恒力F_x和沿y軸正向的恒力F_y,則(    )

圖5-1-6

A.因?yàn)橛蠪_x,質(zhì)點(diǎn)一定做曲線運(yùn)動(dòng)

B.如果F_y＞F_x,質(zhì)點(diǎn)向y軸一側(cè)做曲線運(yùn)動(dòng)

C.如果F_y=F_xtanα,質(zhì)點(diǎn)做直線運(yùn)動(dòng)

D.如果F_x＞F_ycotα,質(zhì)點(diǎn)向x軸一側(cè)做曲線運(yùn)動(dòng)

Answer 1

解析：質(zhì)點(diǎn)是否做曲線運(yùn)動(dòng),關(guān)鍵看F_x與F_y的合力與速度v₀是否在同一直線上,不是因?yàn)橛蠪_x的存在而做曲線運(yùn)動(dòng),也不因?yàn)槟膫�(gè)力大而做曲線運(yùn)動(dòng).當(dāng)F_y=F_xtanα?xí)r,F_x與F_y的合力與速度v₀同向,質(zhì)點(diǎn)一定做直線運(yùn)動(dòng);當(dāng)F_x＞F_ycotα?xí)r,F_x與F_y的合力與x軸的夾角小于α,質(zhì)點(diǎn)向x軸一側(cè)做曲線運(yùn)動(dòng).

答案：CD