Operation Guide-Lab 2 Torsional Pendulum Contents 1. Familiarize yourself with the operation of the device, Adjust the device carefully so that it is ready for the measurement Such as: learn how to operate the digital timer, adjust the stage so that the device is placed horizontally(please discuss with your partner why we need to do 2. Determine the torsional constant K of the spiral spring with a plastic cylinder 1)Install the object holder. Adjust the chopping bar, so that it can block the light from the diode to the detector when it moves. Measure the time duration for 5 periods of the torsional pendulum with only the object holder to. So the period: To==to Data table no. 1 to/s 2) Measure the mass of the plastic cylinder with an electric balance(one measurement is enough)and its diameter for 3 times with a vernier caliper. Install the plastic cylinder to the object holder. Measure the time duration for 5 periods of the torsional pendulum with the object plastic cylinder t. So the period: T=-t Data table no. 2: erage D/cm / K t The experimental expression of inertia of the object holder lo: I 4 t The theoretical expression of inertia of the plastic cylinder Ipe t The total moment of inertia of the object holder and the plastic cylinder I K 1=10+/ The expression of the torsional constant K can be derived easily as Substitute the measurement results of the qualities of data table 2 into the above expression of K, get the K value and estimate the Uncertainty. Write down the calculation process 3. Measure the moment of inertia of differently shaped objects: a metal barrel, an iron ball and a long-thin metal bar(Optional). Compare the measured results the theoretically alculated values 1) The metal barrel a) Measure the time duration for 5 periods of the torsional pendulum with the object10 Operation Guide——Lab 2 Torsional Pendulum Contents 1. Familiarize yourself with the operation of the device. Adjust the device carefully so that it is ready for the measurement. Such as: learn how to operate the digital timer; adjust the stage so that the device is placed horizontally (Please discuss with your partner why we need to do so?). 2. Determine the torsional constant K of the spiral spring with a plastic cylinder. 1) Install the object holder. Adjust the chopping bar, so that it can block the light from the diode to the detector when it moves. Measure the time duration for 5 periods of the torsional pendulum with only the object holder t0. So the period: 0 0 1 5 T t  . Data table No. 1: No. 1 2 3 Average t0 / s 2) Measure the mass of the plastic cylinder with an electric balance (one measurement is enough) and its diameter for 3 times with a vernier caliper. Install the plastic cylinder to the object holder. Measure the time duration for 5 periods of the torsional pendulum with the object plastic cylinder t. So the period: 1 5 T t  . Data table No. 2: No. 1 2 3 Average D / cm t/ s m / g  The experimental expression of inertia of the object holder I0: 2 0 0 2 4 K I T   ；  The theoretical expression of inertia of the plastic cylinder Ipc: 1 1 2 2 2 8 PC I mr mD   ；  The total moment of inertia of the object holder and the plastic cylinder I: 2 0 2 4 pc K I I I T     ； The expression of the torsional constant K can be derived easily as: K= . Substitute the measurement results of the qualities of data table 2 into the above expression of K, get the K value and estimate the Uncertainty. Write down the calculation process. 3. Measure the moment of inertia of differently shaped objects: a metal barrel, an iron ball and a long-thin metal bar (Optional). Compare the measured results with the theoretically calculated values. 1) The metal barrel： a) Measure the time duration for 5 periods of the torsional pendulum with the object