Pull the string through the glass rod so that approximately 0.6 m of string is between the glass rod and stopper. Practice swinging the stopper around in a circle over your head as shown in Figure 7 while holding onto the glass rod with one hand and supporting the suspended mass containing the washers with the other. Note: Be careful and review the safety precautions at the beginning of this procedure. Swing the stopper in a circular motion, while slowly releasing the hanging mass and adjusting the rotating speed of the stopper so that the paper clip attached to the string above the washers stays a few centimeters below the bottom of the tube, neither rising nor falling. Note: Do not move your hand too much while swinging the stopper. Ideally, the steel washers should be stationary. Keeping your hand steady will help the rubber stopper move smoothly. Practice stopping the spin while simultaneously grasping the string just above the tube. This action will allow you to measure the radius of the spin circle, which is the length of the string from the top of the tube to the center of the stopper. Stop spinning the rubber stopper and use