75. (a) The frequency for small amplitude oscillations is fgL=12//πaf, where Lis the length of the pendulum. This givesf==980200352/(./)/(.)..πafmsmHz(b) The forces acting on the pendulum are the tension force GTof the rod and the force of gravitymgG. Newton’s second law yields GGGTmgma+=, where mis the mass and Gais the acceleration of the pendulum. Let GGGaa ae=+′, where Gaeis the acceleration of the elevator andG′ais the acceleration of the pendulum relative to the elevator. Newton’s second law can then be written ()emg aT−+=GGGma′G. Relative to the elevator the motion is exactly the same as it would be in an inertial frame where the acceleration due to gravity is
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