Answer:
An external force F is required
Step-by-step explanation:
According to Newtons law of motions
Law 1 states that everybody will continue to be at rest or uniform motion in a straight line unless compelled to change that state by an external force
Law 2 states that the rate of change of momentum of a body is proportional to the external force and takes place in the direction of the force
Law 3 states that to every action there must be an opposite reaction