1. http://paer.rutgers.edu/PT3/experiment.php?topicid=5&exptid=177 The three black stoppers that are whirling in a circle have a combined mass of 58.7g. The length of man's arm from elbow to wrist is about 30 cm. 2. Find the mass of the other object that is tied at the bottom. 3. I solved for time by first counting the number of frames it takes to complete a full circle, which was approximately 18. Then since the video is 30 frames per second, I set up a proportion (18/30 = t/1), where t=time. I then assumed that the radius was 30 cm. which I am very unsure on. I plugged in radius into C=2(pie)(r) to solve for the circumference. I divided the circumference by the time to find velocity (does this even make sense?) Then since F=m(v2/r), I plugged in mass (58.7), velocity, and radius to solve for force. I was also able to figure out acceleration since F = ma, but honestly I'm not sure if my steps so far are correct. And how would I go about solving the mass of the other object tied at the bottom?