GATE 2021 PI – Question 61
The shown rigid members AB,BC,CA form an equilateral truss, with pin A and frictionless roller C. A downward 10 kN force acts at B. Neglect member weights. Find BC force in N to one decimal, negative for compression and positive for tension.
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Correct answer: -5773.7 to -5773.4
Explanation
Symmetry gives equal AB and BC forces. At B both compressive members supply upward components: $2F\sin60^\circ=10000$. Therefore magnitude F = 10000/√3 = 5773.50 N. With compression negative, **F_BC = −5773.5 N**.