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December 9th, 2018, 04:59 PM   #1
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Help me on equilibrium

Anyone help me!!! How do I solve this, members explain to me, please, and do I need diagram for this? Help. I'm a nonentity, I need a step by step explanation. I don't even know whether it is rotational or translational. Help me, please.


A uniform horizontal beam AB of mass 30kg and length 2m rest on a fulcrum at F distance 102cm from A. Masses of 2kg, 3kg, 4kg and 5kg are hung at C, D, G and H, which are 24cm, 60cm, 120cm and ycm from A respectively. Find the value of y.
2. The reaction R at point E

Last edited by skipjack; December 11th, 2018 at 04:13 PM.
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December 9th, 2018, 09:50 PM   #2
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Beam.png
I've provided a diagram, but you'll realize that it isn't needed. I'll assume that gravity is acting downwards (i.e. the curvature of the earth is to be ignored).

As the beam "rests on a fulcrum", I'll also assume the beam is in equilibrium.

I can now write the (simplified) equation below, in which each term represents a moment (about the fulcrum), which is force (due to gravity) times (horizontal) distance from the fulcrum. I've omitted all units and g (the acceleration due to gravity), as they're the same for each term.

2(102 - 24) + 3(102 - 60) + 30(102 - 100) = 4(120 - 102) + 5(y - 102)

That simplifies to 342 = 5y - 438, so y = 780/5 = 156.

As the beam is uniform, its mass is treated as though it's entirely at a point halfway along the beam.

Is the question about R mistyped? There's no information in the question about point E.
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