Assuming there is not friction or air resistance, which of the following is true about total mechanical energy of a swinging pendulum?

It is the greatest at the top

It remains constant throughout the entire swing

It is zero the entire time

It is the greatest at the bottom

The answer is: It remains constant throughout the entire swing.

Explanation:

The "total mechanical energy" refers to the sum of the potential energy and the kinetic energy. When it comes to swinging pendulum, the total mechanical energy refers to the sum of the "gravitational potential energy" and the "kinetic energy."

Remember that the pendulum is "not in free fall" because it is constrained by a string. The tension in the string is being balance by a gravitational force that is acting on it. So, when the pendulum swings (back and forth), the gravitational potential energy and the kinetic energy undergoes a constant exchange of energy. So, this allows the mechanical energy to be conserved.

If friction is present, the mechanical energy will then be turned into other forms of energy.