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Unformatted text preview: MASSACHUSETTS INSTITUTE OF TECHNOLOGY Physics Department Physics 8.01 Fall Term 2010 Experiment 04: Angular Momentum Purpose of the Experiment: In this experiment you investigate rotational collisions and the conservation of angular mo- mentum in rigid body rotational dynamics. It is the rotary counterpart of linear collisions. The heart of the experiment is a high quality DC motor to spin a rotor up to several hundred radians per second. When power to the motor is shut off, it serves as a tachometer-generator whose output voltage is proportional to the angular velocity of the rotor; thus the angular velocity of the rotor can be determined by measuring the output voltage. When you hold down the red pushbutton to switch on the apparatus, power is applied to the motor; when you release it, the rotor coasts and the output voltage the motor generates can be read by the computer. This experiment will give you experience in measuring and calculating moments of inertia, measuring and calculating the effects of external torques, including torque due to friction, and determining the changes in angular momentum during inelastic rotational collisions. Experimental Materials: Logger Lite Software Vernier LabPro Interface Angular Momentum Apparatus with 3 brass/Velcro disks and power cord 2 Vernier Differential Voltage Probes 1 m (table height) length of string 50 gm weight/hanger Setting Up the Experiment: Plug the rotary motion apparatus into its power supply; you should see the LED in the plastic pipe elbow come on. Experiment 04 1 November 9/10, 2010 The experiment is longer than any we have done before and has two parts; extra time has been allotted to do it. First, you will calibrate the equipment and measure the moment of inertia of the rotor. Second, you will use the calibrated apparatus to study rotational collisions. At the start of the experiment, use two voltage probes to connect the output from the appa- ratus to channel 1 and 2 on the Logger Lite interface. Connect the generator output voltage (the jacks farthest from the power input connector) to channel 1 and the phototransistor output to channel. The data acquisition and analysis for both experiments will be done with the Logger Lite program called AngularMomentum.gmbl . It is there because two calibrations must be done in this experiment. Before you can carry out any rotational collision measurements, you must first calibrate the tachometer-generator and then you must measure the moment of inertia of the rotor. These are the tasks of Part I; in Part II you will study rotational collisions. The first task is to calibrate the tachometer generator output, i.e., what is for 1V output?...
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