I am working on HS Physics teacher certification, the study guide lists one the competencies as follow: "Identifies and applies Newton's laws to analyze and solve a variety of practical problems (e.g., properties of frictional forces, acceleration of a particle on an inclined plane, displacement of a mass on a spring, forces on a pendulum)." Does anyone know the formula for "force on a pendulum"? I know only the period for pendulum. Keep in mind that this is introductory-level physics, any help from experts out there would be very much appreciated. Thanks for your time and effort.