物体A单独放在倾角37°的斜面上时,正好能匀速下滑：
mAgsin37° = μmAgcos37°
μ = tan37° ≈ 3/4
a系上细绳通过光滑滑轮挂上物体B且将倾角改为30度,A正还能沿斜面匀速上滑：
mBg = mAgsin30° + μmAgcos30°
mB/mA = sin30° + μcos30°= 1/2 + 3/4*√3/2 = (4+3√3)/8 ≈ 9.196/8 ≈ 6/5
A