Experiment 9: Angular Momentum MIT 8.01T Physics IGoal To investigate conservation of angular momentum and kinetic energy in rotational collisions. Measure and calculate moments of inertia. Measure and calculate non-conservative work in an inelastic collision.Apparatus : Phototransistor connects to channel A of 750. Tach-generator to channel B. Connect power supply. Red button applies power to motor. Put black sticker or tape on white plastic rotor for tachometer-generator calibration.Calibrate Tachometer-generator: Spin motor up to full speed, let it coast. Sample Rate: 5000 Hz, and Sensitivity: Low. Measure and plot voltages for 0.25 s period. Time for 10 periods to measure ω. Average the output voltage over the same 10 periods. Then calculate ω for 1 V output.Measure Rotor IR : Plot only the generator voltage for rest of expt. Use a 55 gm weight to accelerate the rotor. Sensitivity: Low Sample rate 500 Hz. Delayed start: None Auto Stop: 4 seconds Start DataStudio and let the weight drop.Graph: Generator voltage while measuring IR. What is happening: 1. Along line A-B ? 2. At point B ? 3. Along line B-C ? How do you use this graph to find IR ?Measure IR Results: Measure and record αup and αdown. For your report, calculate IR. (mr g − rαup)=τf = IRαdown IR α −αdownupFast Collision: Sensitivity Sample Rate Delayed Start Auto Stop Low 200 Hz 1 sec Falls below 0.5V Find ω1 (before) and ω2 (after), estimate δt for collision. 2ω(Calculate IW = 1 mr − ri 2)o2Slow Collision: Find ω1 and ω2 , measure δt , fit or measure to find αc. Keep a copy of your results for the homework
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