Final answer:
Leonardo da Vinci's blocks began to slide at an angle of approximately 14.04 degrees.
Step-by-step explanation:
Leonardo da Vinci conducted quantitative experiments on friction, including measuring the angle at which a block of wood begins to slide on an inclined plane. He reported a coefficient of static friction of 0.25 in his experiments. The angle at which the block begins to slide can be determined using the formula:
Angle of slide = arctan(coefficient of static friction)
Therefore, in Leonardo's experiments, the angle at which his blocks began to slide was approximately 14.04 degrees.