解:F,=ma=m I sin e mg+E+F=0 ∑F=0,Fc0s0-mg=0 F mg ∑ f=0.f Sin0-f=0 解得F7=m8=1.96N cos 0 flin e =2.1m /s解: 2 sin I n v F ma m l  = = + + = 0 FT FI mg    0, cos 0 F F mg b T = − =  0, sin 0 F F F n T I = − =  解得 1.96N cos = =  mg FT s sin 2.1 m 2 = = m F l v T 