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The mass of the lever just adds or subtracts from any other external force(s) applied to the lever - depending on the direction of the external force relative to the direction of gravity.

So a heavy wrench is helpful when pushing down, while loosening a rusty nut. But a light carbon fibre wrench would be better when pulling up.

How much torque gravity adds or subtracts in that case is also dependent on the distribution of mass along the length of the lever.

And to add to the fun, the mass of the leaver does add momentum into the equation, which comes into play as extra work required when changing speed of the rotation (e.g. starting, stopping the turn). And how much momentum also depends on the distribution of mass along the length of the lever.






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