Question

已知物块A的重为G,滑轮O的半径为R,绞车B的半径为r,绳索与水平线的夹角为β.

Answer 1

（1） A的加速度为0,有F=P,M=rF = rP

(2)A的加速度为a≠0,则F = P+ma = P(1+a/g) M = rF = rP(1+a/g)

（3）J = Pr^2/2

F = M/r

Fh = mv^2/2+(mr^2/2)*(v/r)^2/2

Mh/r = 3mv^2/4

v = 2*sqrt(Mh/3rm) = 2*sqrt(Mhg/3rP)

a*P/g = F - P

a = Fg/P - 1 = Mg/rP - 1

Fo = 2P*sin((π/2+β)/2) = 2P*sin(π/4+β/2) = √2*P*(sin(β/2)+cos(β/2))

与垂线所夹角为π/4-β/2,方向向左上方.