Measure the diameter of the spindle with the string wrapped around it. Level the A-base. Review the procedures from the Centripetal Force experiment. Slide the center post along the size groove to the center of the rotating platform. Insert a screw 20.5 cm away from the center post. Verify that it's on the proper side of the center post. Slide the square mass into the top groove until it touches the screw. Lock the square mass at this location. Insert another screw 4.5 cm away from the center post. Verify that it's on the same side of the rotating platform as the other screw. Connect the rotational motion sensor to the interface. Start up the laptop and open the PHYS 4A PASCO Files folder on the desktop. Double-click on the "Rotational Motion Sensor.cap" file. Turn on the rotational motion sensor and pair it to your interface. Verify that you're not paired to another group's photogate. Unwind string from the spindle until it hangs over the pulley. Attach a mass of 100 g onto the string. Record the exact mass. Start recording data and simultaneously release the hanging mass from rest. Stop recording data when either the mass hits the