Q.294. Mechanics involving moments of forces.

Question 294.
Determine the size of the reaction forces at the two supports on a beam in the following figure.

Answer 294.
Let N1 and N2 be the reaction forces at the left and right supports.

Taking moments of all forces about the point of contact of the right support,
40 * (3.0) - N1 * (1.6) + 24 * (0.8) - (20) * 1 = 0
=> N1 = 74.5 kN

Taking moments of forces about the point of contact of the left support,
40 * (1.4) - 24 * (0.8) + N2 * (1.6) - 20 * (2.6)
=> N2 = 9.5 kN

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Upward reactive forces, N1 + N2 = 74.5 + 9.5 = 84 kN.
Sum of downward forces = 40 + 24 + 20 = 84 kN.

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