An object has a constant velocity unless there is a net force acting on it.
Newton's Second Law:
The rate of change of momentum with time is proportional to the net applied force and is in the same direction.
Newton's Third Law:
For every action (force) there is a reaction force and the action and reaction forces are equal in magnitude, opposite in direction, and act upon different bodies.
Note: An object's weight is not a measurement of mass, but a measurement of force. Weight is equal to an object's mass multiplied by the standard acceleration of gravity given our planet's mass and a specific distance from the center of mass [w = mg (g » 9.80665 m/s2)]. So, 1 kg accelerated at 9.80665 m/s2 is almost exactly 2.2 lbs. The English unit for mass is actually called a slug. 1 slug accelerated at 1 ft/s2 = 1 lbs. This unit of measurement is no longer used to my knowledge.