2 options: strain energy watts reaction force energy potential energy work power 1. Energy stored within an object due to its vertical position or deformation; expressed as units of force times units of length or as joules in SI; a scalar quantity. 2. Rate of doing work; work done divided by time; measured in units of work divided by units of time or expressed as watts in SI; a scalar quantity. 3. An external contact force that results when one object touches another. 4. Energy due to the deformation of an object; for stretching or compressing, it is equal to half the stiffness constant of the material times the square of change in length of the object; expressed as units of force times units of length or as joules in SI; a scalar quantity. 5. SI unit of measure for power; equal to 1 J/s. 6. The product of force exerted on an object times the displacement of the object at the point of application of the force along the line of action of the force; expressed as units of force times units of length or as joules in SI; a scalar quantity