3. There are several periodic motions associated with Earth. One is that Earth rotates once every 24 hours. List at least two other examples, and give the period of each. 4. Which of the four experiments below has the longest period? Why? A B C D 48 cm 39 cm 28 cm 21 cm 10 10 15 25 Small mass Medium mass Large mass Large mass Hit S. CHALLENGE! A pendulum swings past its pole 20 times in 18 seconds. What is the period of the pendulum? Name Date 1. Which pictures show harmonic motion? Circle all the correct answers and describe the harmonic motion in each correct answer. A B G D E 2. Match the four measured periods with the most likely pendulum