explain why sliding friction is less than static friction
Sliding friction refers to the force that opposes the motion of an object as it slides against another surface. Static friction, on the other hand, is the force that prevents the relative motion between two surfaces when they are at rest relative to each other. The key factor that causes sliding friction to be generally less than static friction lies in the nature of the contact between the surfaces.
When two surfaces are at rest relative to each other, the irregularities and microscopic bumps on their surfaces interlock and create stronger bonds between them, resulting in higher static friction. This interlocking mechanism allows the surfaces to "stick" together, making it harder to initiate motion.
When an external force is applied to overcome static friction and set the object in motion, the surfaces now experience sliding friction. During sliding motion, the interlocking between the surfaces is broken, and the irregularities on their surfaces slide past each other. This sliding motion reduces the contact area between the surfaces, decreasing the strength of the intermolecular bonds and resulting in lower sliding friction compared to static friction.
Apart from the reduced contact area, other factors contribute to the lower sliding friction. Sliding friction involves the surfaces rubbing against each other, which leads to the generation of heat and energy losses due to frictional forces. This dissipation of energy further reduces the sliding friction compared to the typically higher static friction.
In summary, sliding friction is generally less than static friction because the interlocking mechanism is broken during sliding motion, resulting in a decreased contact area and weaker intermolecular bonds between the surfaces. Additionally, the energy losses due to sliding friction further contribute to its lower value compared to static friction.