December 9th, 2018, 03:59 PM  #1 
Member Joined: Aug 2018 From: Nigeria Posts: 73 Thanks: 2  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 03:13 PM. 
December 9th, 2018, 08:50 PM  #2 
Global Moderator Joined: Dec 2006 Posts: 20,644 Thanks: 2084  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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