Frictionless plane
![Key:N = normal force that is perpendicular to the planem = mass of objectg = acceleration due to gravityθ (theta) = angle of elevation of the plane, measured from the horizontal](/Images/godic/202501/14/Free_body_frictionless.svg5206.png")
The frictionless plane is a concept from the writings of Galileo Galilei. In his 1608 The Two New Sciences, Galileo presented a formula that predicted the motion of an object moving down an inclined plane. His formula was based upon his past experimentation with free-falling bodies. However, his model was not based upon experimentation with objects moving down an inclined plane, but from his conceptual modeling of the forces acting upon the object. Galileo understood the mechanics of the inclined plane as the combination of horizontal and vertical vectors; the result of gravity acting upon the object, diverted by the slope of the plane.