Question

A 4-m long, 150-kg steel beam is attached to a wall with one end connected to a hinge that allows the beam to rotate up and down. The other end of the beam is held in a horizontal position with a cable that makes a 27° angle with the beam and is attached to the wall (see (Figure 1)). What is the tension force that keeps this beam in static equilibrium?

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Answer 1

net τ = τ_cable - τ_gravity = 0

τ_gravity = m * g * (L / 2)       note: L/2 b/c that's where center of gravity is

τ_ = F_t * sin(27 degrees) * L

F_t * sin(27) * 4 - 150 * 9.8 * (4/2) = 0

F_t = 1620N