On contact and motion: friction of a sliding weight
Rules holding that the drag of a load sliding on a level plane is half its weight
Under the heading "On contact and motion," the folio sets down rules of friction: the force needed to slide a weight across a level plane is always half the weight moved, and a body gives more detriment at its contact when it rests on a smaller face. A further rule holds that the friction of a moving weight is the same whether the contact is large or small. At the right margin are numbered figures (70, 71) in which the value 4 is repeated along stacked blocks to tally contact, together with a spherical form, a ring, and a many-spoked wheel.
On this page
Sliding friction equals half the weight moved
The force used in the rubbing motion made upon a level plane is always half the weight it moves. A weight also gives more detriment at its contact the smaller the face on which it is set.
Friction independent of the area of contact
The friction of the motion of weights made with much contact gives its mover as much fatigue as if it were made with little contact. The proportion that suffices for the agent against the patient weight barely exceeds that of the patient against the moving agent.
Wheel, ring and roller studies
Pen sketches at the right illustrate the friction rules with mechanical forms: a spherical vessel-like body, a ring, and a wheel drawn with many curved spokes. Numbered figures (70, 71) tally repeated units of contact along stepped blocks.