Notes and Drawings on the Thorax and Abdomen

Because a weight does not move except along the line which is most perpendicular to the center of the world Leonardo refers to the "center of the world" as the center of gravity or the center of the Earth, therefore a weight will move so much more swiftly along a given line the further that line is from the said perpendicular.

Motion made along lines which do not pass through the center of this world cannot be of the same velocity nor of the same force, as they lack one of the two principal conditions: namely, velocity and perpendicularity between the line of motion and the line of the horizon.

The closer the line of descent? approaches the horizontal, the more its natural power is diminished.

On the nature of heavy bodies

If a weight is suspended by a cord, it will come to rest directly beneath the point of suspension. This is because its natural desire Leonardo often personifies physical forces, using "desire" to describe the inherent tendency of objects to seek the center of gravity is to move toward the center of the Earth by the shortest possible path.

OF THE MOTION OF THE ELEMENTS

All heavy things seek to descend, and all light things seek to ascend. But when a weight is placed upon an inclined plane, its motion is governed by the angle of that plane. The steeper the slope, the faster the fall.

Gravity is a localized power

As the weight falls, it acquires accidental force This is an early concept of momentum or kinetic energy gained during acceleration which increases in proportion to the distance traveled. This force is what allows a falling body to strike with a power far greater than its simple weight when at rest.