SimReal SimReal - VPython - GlowScript - Trinket - Physics - k05 - Force Newton's Second Law - Force and Motion: Newton's Second Law: F = ma F is the vector sum of the external forces on a given system, m is the mass of this system and a is the acceleration vector of the center of mass of this system. This application is a simulation of the motion of a particle (blue color) influenced of a single external force (green color). Click 'Run' and you will see the particle (blue) in the simulation window. Drag the blue particle to see the force (green color) you are using on the particle to illustrate the force (size and direction) applied to the particle. When a force (green) is acting on the blue particle, the particle will have an acceleration according to this force. In the simulation window you will see both the particle (blue color) force vector (green color), the velocity vector (red color) and the path (blue color). Notice how the particle will continue with constant velocity when no force is acting. The particle is changing direction when colliding with the grid wall (elastic collision).