Gifts Sale - for science moms, dads & grads
Gifts Sale - for science moms, dads & grads


Why doesn't friction depend on surface area?
Asked by: Elizabeth Stewart


Although a larger area of contact between two surfaces would create a larger source of frictional forces, it also reduces the pressure between the two surfaces for a given force holding them together. Since pressure equals force divided by the area of contact, it works out that the increase in friction generating area is exactly offset by the reduction in pressure; the resulting frictional forces, then, are dependent only on the frictional coefficient of the materials and the FORCE holding them together.

If you were to increase the force as you increased the area to keep PRESSURE the same, then increasing the area WOULD increase the frictional force between the two surfaces.
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor

Get $10 OFF glasses at

Science Quote

'A theory with mathematical beauty is more likely to be correct than an ugly one that fits some experimental data. God is a mathematician of a very high order, and He used very advanced mathematics in constructing the universe.'

Paul Dirac

All rights reserved. © Copyright '1995-'2017