page_title: Potential energy
section_title: Potential energy for near Earth gravity
hierarchical_section_title: Potential energy / Potential energy for near Earth gravity
caption_attribution_description: English: Trebuchet at Château des Baux, France (reconstruction) - author: ChrisO中文: 法國莱博德城堡的投石機（重建）
context_page_description: In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.
  Common types of potential energy include the gravitational potential energy of an object that depends on its mass and its distance from the center of mass of another object, the elastic potential energy of an extended spring, and the electric potential energy of an electric charge in an electric field. The unit for energy in the International System of Units is the joule, which has the symbol J.
  The term potential energy was introduced by the 19th-century Scottish engineer and physicist William Rankine, although it has links to Greek philosopher Aristotle's concept of potentiality.
  Potential energy is associated with forces that act on a body in a way that the total work done by these forces on the body depends only on the initial and final positions of the body in space. These forces, that are called conservative forces, can be represented at every point in space by vectors expressed as gradients of a certain scalar function called potential.
context_section_description: For small height changes, gravitational potential energy can be computed using
  where m is the mass in kg, g is the local gravitational field (9.8 metres per second squared on earth), h is the height above a reference level in metres, and U is the energy in joules.
  In classical physics, gravity exerts a constant downward force F=(0, 0, Fz) on the center of mass of a body moving near the surface of the Earth.  The work of gravity on a body moving along a trajectory r(t) = (x(t), y(t), z(t)), such as the track of a roller coaster is calculated using its velocity, v=(vₓ, vy, vz), to obtain
  where the integral of the vertical component of velocity is the vertical distance. The work of gravity depends only on the vertical movement of the curve r(t).
caption: A trebuchet uses the gravitational potential energy of the counterweight to throw projectiles over two hundred meters
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