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A friend wishes to know the effect on the amplitude by adding three quarters on the top of a 77kg pendulum bob (the tower clock at the county building in Santa Barbara.*
The period change was quite obvious and measurable.** However, there was no detectable change in the amplitude. After some cogitation (I'm a bit slo these days.) I conclude that adding mass on the "down swing" will do nothing, but on the upswing will reduce the amplitude. I found the KE at BDC and concluded the energy to lift the quarters (~ 0.02kg) is so little the reduction in height, (h = L(1-cos(A)), is on the order of microns, and, therefore, not measurable by his method. [speed as measured by a photogate at BDC] ...