# A classical mechanics problem by kelvin hong 方

There is a unit tetrahedron $$ABCD$$ with face $$BCD$$ on the ground. Edge $$CD$$ is fixed to the ground so that vertex $$B$$ can be lifted up. Now, James wants to exert a force horizontally on point $$A$$ and turn over the tetrahedron, making vertex $$B$$ the new apex with face $$ACD$$ on the ground.

If the mass of the tetrahedron is $$m$$, and the minimum force that is necessary to pull it can be expressed as $$\frac{mg}{a\sqrt{b}}$$, where $$b$$ is a square-free number, then submit $$a+b$$.


Details and Assumptions:

• $$g$$ is the gravitational acceleration.
• A unit tetrahedron is a tetrahedron with all six sides of length 1.
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