When a block of metal is initially at rest on a heated surface, what effect does increasing the temperature have on the static friction coefficient compared to the kinetic friction coefficient once the block starts sliding?

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Seekh · Accepted Answer

When you heat a metal block that sits on a hot surface, the metal’s surface becomes smoother and its internal vibrations increase. This heating lowers the static friction coefficient more than it lowers the kinetic friction coefficient, because static friction depends more on the microscopic contact points that are disrupted by heat. As a result, the block needs less force to start moving than it would at a lower temperature. Once the block begins to slide, the kinetic friction coefficient remains relatively high, so the block’s speed is less affected by the temperature increase. For example, a steel block on a heated plate may need only half the force to start sliding compared to when it is cold, while its sliding resistance stays almost the same.

When a block of metal is initially at rest on a heated surface, what effect does increasing the temperature have on the static friction coefficient compared to the kinetic friction coefficient once the block starts sliding?

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