Question

A pendulum has 484 J of potential energy at the highest point of its swing. How much kinetic energy will it have at the bottom of its swing?

Answer 1

-- Energy is never created or destroyed.

-- No energy is added to the pendulum during its swing.

-- If we ignore air resistance and friction, then no energy is lost
from the pendulum during its swing.

-- Therefore the total energy of the pendulum must be constant.

-- Any potential energy lost at any point in the swing
must show up as kinetic energy.  If it had 484J at the top,
then it'll have 484J at the bottom.