Question

You know that the force of friction depends on the nature of the surfaces in contact. Does it also depend on how hard the surfaces press each other? Is the friction acting on an object that is about to move larger than the friction after motion begins? Is the friction which acts on a rolling object less than that on a sliding object? Find answers to these questions and create an infographic. Such observations help explain why the invention of the wheel was a major milestone in human history.

Answer 1

The type of surfaces and the force with which they press against one another determine friction. Before motion starts, static friction is higher than sliding friction. Because rolling friction is far lower than sliding friction, the wheel greatly reduced motion resistance, transforming human history.

The 4 Laws of Friction

Depends on surface nature?	Yes	Compared to smooth surfaces, rougher surfaces have more microscopic imperfections that interlock, increasing friction.
Depends on hard pressing?	Yes	Friction increases as surfaces are compressed harder (normal force), which causes their imperfections to interlock more.
Before vs. after motion?	Yes	When at rest, static friction is greater than kinetic or sliding friction. Starting to move an object requires more work than maintaining it.
Rolling vs. sliding?	Yes	Because rolling reduces the interlocking of surface flaws, it is significantly less frictional than sliding.

The invention of the Wheel Was a Major Milestone because:

High-resistance sliding action is transformed into significantly lower-resistance rolling motion by the wheel. Early humans used wheels to transport heavy objects with exponentially less physical effort, as opposed to dragging huge loads and battling the high coefficient of sliding friction.