A push or a pull.
The combination of all forces acting on an object.
Two or more forces whose effects cancel each other out and do not change the motion of an object.
Two or more forces acting on an object that do not cancel, and cause the object to accelerate.
Newton's first law of motion
If the net force acting on an object is zero, the object will remain at rest or move in a straight line with a constant speed.
Force that acts to oppose sliding between two surfaces that are touching.
Newton's second law of motion
An object acted upon by a net force will accelerate in the direction of the force, and the acceleration equals the net force divided by the object's mass.
Gravitational force between an object and Earth.
Center of mass
Point in an object that moves as if all of the object's mass were concentrated at that point.
Newton's third law of motion
Forces always act in equal but opposite pairs.