Which statement best describes energy in an open system?

all energy and matter are contained within the system.
energy and matter flow into and out of the system.
matter flows into and out of the system; energy does not.
there is no energy in an open system; there is matter.

Energy and matter flow into and out of the system.

Explanation: There are three types of system:

Open System: A system where mater and energy both can pass across the boundary. Example: Tea kept in a cup

Closed system: A system where mater can not be exchanged but energy can be exchanged. Example: Tea kept in a kettle

Isolated System: A system where neither mater nor energy both can be exchanged.  Example: Tea kept in a thermos

number of electrons for neutral cl

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.