An object with mass 'm' moving with velocity 'V' has kinetic energy of \\\\(\\dfrac{1}{2}m{v}^{2}\\\\) . In order to bring it to rest, its velocity has to be reduced to zero, and in order to accomplish that, the kinetic energy has to be drained off and sent somewhere else. An external force has to absorb energy from the object, i.e. do negative work on it, equal to its kinetic energy,or\\\\(-\\dfrac{1}{2}m{v}^{2}\\\\).