Calculating Moment & Horizontal Force at O for 100 lb Force

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SUMMARY

The discussion focuses on calculating the moment and horizontal force at point O due to a 100 lb vertical force applied to a lever. The moment about O is determined using the formula Mo = Fd, where F is the force and d is the perpendicular distance. The correct distance is calculated as 24 inches multiplied by the cosine of 60 degrees, resulting in Mo = 100 lb * 24 in * cos(60). The confusion arises from the need for the perpendicular distance rather than the horizontal component, which is clarified in the discussion.

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Homework Statement


A 100 lb vertical force is applied to the end of a lever, which is attached to a shaft at O. Determine (a) the moment of the 100 lb force about O (b) the horizontal force applied at a that creates the same moment about O.

Homework Equations

The Attempt at a Solution


I know the solution but I'm still a bit confused as to what I'm doing for part (a) I have Mo = Fd = 24in*cos(60) * 100 lb
But I don't understand why I'm using
24in*cos(60) and not 24in*sin(60)...

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David Donald said:
But I don't understand why I'm using
24in*cos(60) and not 24in*sin(60)...
You need the perpendicular distance between O and the line of action of the force.
 

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