Shoulder pain is any pain in or around the shoulder joint. When tendons become trapped under the acromion, the rigid bony arch of the shoulder blade, it can cause shoulder pain called impingement syndrome.
The period for a simple pendulum does not depend on the mass or the initial anglular displacement, but depends only on the length L of the string and the value of the gravitational field strength g, according to The mpeg movie at left (39.5 kB) shows two pendula, with different lengths.
Contrary to intuition, an earthquake does not make the pendulum swing. Instead, the pendulum remains fixed as the ground moves beneath it. A pendulum with a short period (left) moves along with the support and registers no motion. A pendulum with a long period (right) tends to remain in place while the support moves.