Posted by Stephanie on Friday, April 22, 2011 at 12:54am.
A 30lb weight is attached to one end of a 6ft uniform beam whose own weight is 20lb. Where is the balance point of the system? I know the answer is "1.2 ft from the 30lb weight" but I can't figure out how to get there. Please help. Thanks...

Physics  drwls, Friday, April 22, 2011 at 6:27am
Let x be the distance (in feet) of the balance point from the end with the 30 lb weight.
The total moment about the balance point must be zero, if the beam is balanced. The beam's weight acts through the center of mass and exerts a moment of (3x)*20 ftlb about the pivot point.
This equals the moment (of opposite sign) due to the added weight, which is 30*x. The center of mass and the added weight are on opposite sides of the balance point.
Solve (3x)*20 = 30x
60  20x = 30x
60 = 50x
x = ___

Physics  lemuel, Thursday, May 22, 2014 at 9:39pm
1.2

Physics  CEANORSU, Saturday, March 5, 2016 at 2:44am
30x20(6x)=0
30x120+20x=0
50x120=0
50x=120
x=2.4 ft
the balance point is 2.4ft from the 30lb weight.
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