对垂直于斜面和平行于斜面两个方向按牛顿第二定律列方程
N-mgcos30°=masin30°
F-mgsin30°=-macos30°
(1)N=0时有a = -g cot 30° = -9.8*√3= -17m/s2
(2) N=masin30°+mgcos30°= -10*5*1/2 + 10*9.8*√3/2 = 60N
F = mgsin30°-macos30°= 10*9.8*1/2 - 10*(-5)**√3/2 = 92.3N
(3) N=masin30°+mgcos30°= -10*20*1/2 + 10*9.8*√3/2 =-15.23N
支持力为负说明球已离开斜面,从而N=0
F = m√(a^2+g^2) = 222.7N
(4) F=0时有
a=gtan30°=9.8*√3/3=5.66m/s2