UNIVERSITY PHYSICS I CHAPTER 5 Newton's law 85.1 Newton's first law of motion and the concept of force 1. Newton's first law of motion Any system in mechanical equilibrium remains in mechanical equilibrium unless compelled to change that state by a nonzero total force acting on the system Osystem-a particle or particles whose motion is to be studied Mechanical equilibrium-a system with a constant velocity is in equilibrium1 1. Newton’s first law of motion Any system in mechanical equilibrium remains in mechanical equilibrium unless compelled to change that state by a nonzero total force acting on the system. 1system—a particle or particles whose motion is to be studied. §5.1 Newton’s first law of motion and the concept of force 2 Mechanical equilibrium—a system with a constant velocity is in equilibrium