The Purpose of this lab is to study the different types of energy. Potential energy is the energy that is stored and not in motion.
Kinetic energy is energy in motion.
When the pendulum reaches the top of the swing it has maximum potential energy and no kinetic energy. When it reaches the bottom or middle of the swing it has a maximum kinetic energy with no potential energy. Also as the pendulum swings it looses kinetic and potenial energy. Tie the string to the ceiling. Place the book in the middle of the string.