What must happens within earth for a volcano to form

Volcanoes on Earth form from rising magma. ... Magma also rises when these tectonic plates move toward each other. When this happens, part of Earth's crust can be forced deep into its interior. The high heat and pressure cause the crust to melt and rise as magma.

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.

the displacement produced by the body.  

the amount of force subjected to the body.  

the angle between the direction of force and displacement