torque question?

Question

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A farmer uses a 2.0m long pry bar to dig a 435 N rock out of his field. The pry bar is jammed under the rock at an angle of 65 dgrees above horiz. how much force does he need to generate to start moving the rock if the fulcrum is .25 m from the end nearest the rock? (ignore weight of the bar, and assume the applied force is perpindicular to the bar)

Answer 1

Start by summing the torques about the fulcrum that are perpendicular to the bar:
The rock
-435*cos(65)*.25
and the force
F*1.75
therefore
F=435*cos(65)*.25/1.75

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