[" If we imagine two ideally smooth surfaces "],[&" if they are kept in contact,the frictional "],[" force acting between them is "]

If we imagine ideally smooth surfaces and it they are kept in contact, the frictional force acting between them is .

With increase of temperature, the frictional force acting between two surfaces

With increase of temperature, the frictional force acting between two surfaces

With increase of temperature the friction force acting between two surfaces .

When two identical spheres are kept in contact, the gravitational force between them is F. If two spheres of same material but with twice the radius are radius are kept in contact, then the gravitational force between them would be

The frictional force between two surfaces is independent of