Problem 4.28

F.B.D. ของวัตถุน้ำหนัก W

จาก \(ΣF_{y}= 0\)

T₁

\(T_{1}\sin (53º) - W = 0\)

\(^{53º}T_{1} =\frac{W}{\sin (53º)}\)

T

จาก \(ΣF_{x}= 0\)

\(T - T_{1}\cos (53º) = 0\)

W

\(T =\frac{Wcos(53º)}{\sin (53º)}= Wcot(53º)\)

F.B.D. ของวัตถุน้ำหนัก w′

จาก \(ΣF_{x}= 0\)

T₂

\(T_{2}\cos (37º) - T = 0\)

\(_{37º}\)

\(TT_{2} =\frac{T}{\cos (37º)}=\frac{Wcot(53º)}{\cos (37º)}\)

จาก \(ΣF_{y}= 0\)

w'

\(T_{2}\sin (37º) - w' = 0\)

\(w' = Wtan(37º)\cot (53º)\)

\(w' =\frac{9W}{16}\;\blacksquare\)