Which of the following statements are TRUE? Select all that apply.

An isolated system is one in which objects inside the system are not influenced by any forces from outside the system.
The mechanical energy of a pendulum bob is maximized at the bottom of its arc.
Mechanical energy is conserved at all times.

An isolated system is one in which objects inside the system are not influenced by any forces from outside the system.

Mechanical energy includes gravitational potential. There is always some friction. The last two statements are false. Elena is correct

The statement "An isolated system is one in which objects inside the system are not influenced by any forces from outside the system" is true. In an isolated system, no external forces are acting on the objects within the system.

The statement "The mechanical energy of a pendulum bob is maximized at the bottom of its arc" is false. The mechanical energy of a pendulum bob is highest at the topmost point of its swing, where it has the maximum potential energy. At the bottom of its swing, the bob has the maximum kinetic energy but minimum potential energy.

The statement "Mechanical energy is conserved at all times" is true. In the absence of non-conservative forces like friction, mechanical energy (the sum of kinetic and potential energy) remains constant throughout a system.

To determine which statements are true, let's evaluate each one:

1. An isolated system is one in which objects inside the system are not influenced by any forces from outside the system.
In order to determine the truth of this statement, we need to understand the concept of an isolated system. An isolated system is one that does not interact with its surroundings, meaning that there are no external forces acting on the objects within the system. This statement accurately defines an isolated system, so it is true.

2. The mechanical energy of a pendulum bob is maximized at the bottom of its arc.
To determine the truth of this statement, we need to consider the physics of a pendulum. The mechanical energy of a pendulum consists of its potential energy (related to its height) and its kinetic energy (related to its motion). At the bottom of its arc, the pendulum bob has its maximum kinetic energy and the minimum potential energy. Since mechanical energy is the sum of these two forms of energy, it is indeed maximized at the bottom of the arc. Therefore, this statement is true.

3. Mechanical energy is conserved at all times.
To assess the truthfulness of this statement, we need to understand the principle of conservation of mechanical energy. According to this principle, mechanical energy is conserved as long as there are no external forces actively doing work on the system. In reality, external forces, such as friction or air resistance, can diminish mechanical energy, making it not conserved at all times. Therefore, this statement is false.

To summarize:
- Statement 1 is true: An isolated system is one in which objects inside the system are not influenced by any forces from outside the system.
- Statement 2 is true: The mechanical energy of a pendulum bob is maximized at the bottom of its arc.
- Statement 3 is false: Mechanical energy is not conserved at all times.