Only Elastic Force k

`k = ( m * v_1 ^2 - m * v_2 ^2)/( x_1 ^2- x_2 ^2)`

`(v_1)"Initial Velocity"`

`(v_2)"Final Velocity"`

`(x_1)"Initial Position"`

`(x_2)"Final Position"`

`(m)"Mass"`

University Physics 12th Edition, Chapter 7, Equation #7.12