PURPOSE: To illustrate the rotational analog of Newton's second law of motion.
DESCRIPTION: Various masses M can be hung on a string wound around an axel of either of two radii R to provide a torque T = MgR. Four brass masses m can be positioned along the arms at one of four distances l from the axis of rotation to provide a moment of inertia I = 4ml^2. The angular acceleration a = T/I = MgR/4ml^2 can then be calculated. The angular acceleration can be determined experimentally by measuring the time required for the system to rotate one complete revolution starting from rest: a = 2 d/t^2, where t is the time required for the device to rotate through the angle d in radians.
REFERENCES: (PIRA 1Q20.20) See Demonstration Reference File for further information, including sample data.
EQUIPMENT: Oberbeck Cross with weights and manual timer.
SETUP TIME: None.
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