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In this problem on the topic of equilibrium and elasticity, we are shown a uniform beam which has a weight of 60 newtons and a length of 3 .2 meters.
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It is hinged at its lower end and a horizontal force of magnitude 5 newton's acts at the upper end.
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The beam is held vertical by a cable making 25 degrees with the ground and is attached to the beam at a height of 2 meters.
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We want to calculate firstly the tension in the cable and next the force on the beam.
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From the hinge.
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Now if we choose an axis through the hinge perpendicular to the plane of the figure and take talks that would cause counterclockwise rotation to be positive, then we require the net torque to vanish since the beam is in equilibrium.
00:48
And this net torque, fl sign of 90 degrees minus t h sign of 65 degrees must equal to zero.
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Here the length of the beam, l, is given to be 3 .2 meters, and the height at which the cable attaches is h, and h is attached at 2 meters.
01:23
And we note that the weight of the beam does not enter in this equation since this line of action is directed towards the hinge.
01:29
So if we take f as 50 newtons, as given in the problem statement, we can rearrange the equation above and solve for t.
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And we get t is equal to f times l over h sign of 65 degrees...