500
Define the Newton's law
First law:In an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.
Second law:In an inertial reference frame, the vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration a of the object: F = ma.
Third law:When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.