A homeowner is trying to move a stubborn rock from his yard which has a mass of

Question

A homeowner is trying to move a stubborn rock from his yard which has a mass of 445 kg. By using a lever arm (a piece of metal rod) and a fulcrum (or pivot point) the homeowner will have a better chance of moving the rock. The homeowner places the fulcrum d = 0.211 m from the rock so that one end of the rod fits under the rock's center of weight. If the homeowner can apply a maximum force of 671 N at the other end of the rod, what is the minimum total length L of the rod required to move the rock? Assume that the rod is massless and nearly horizontal so that the weight of the rock and homeowner's force are both essentially vertical. L =

Explanation / Answer

the moment about the pivot are same

W*d = F*l

445*9.8*0.211 = 871*l

l = 1.056 m

the total length of the rod = L = l+d = 1.267 m <<----answer

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