# conduction through solids

How is heat transferred through two separate bodies which are in contact. The collision of the lattices of atoms of the two bodies is a good answer but if there is a net energy transfer then shouldn't there be a net force on the cooler body to which heat is being transferred to? The molecules of the hotter body should collide with the cooler body and lose some energy and thus transfer some momentum to the cooler body.

Is there actually a net force on a body while there is heat transfer through conduction or is this description of heat transfer insufficient/wrong?

• You say net force, but are you taking into consideration all the possible forces and thus getting net total in one direction? What about friction? Even in a vacuum you'd have to over come an attractive force due to the Van der waals force between the two surfaces.. Feb 15, 2017 at 3:58
• I don't know how much Newtonian mechanics applies here. If it does, then the energy is transfered through collisions between particles in the two substances. By Newton's Third Law, the slower particle (or with lower KE if of different masses) should respond to the faster particle with the same equal-and-opposite force. Feb 15, 2017 at 4:31
• @bpedit So the faster billiard ball will be pushed after a collision with a slower billiard ball back with the same speed? Of course not. Feb 15, 2017 at 4:37
• i mean that if the bodies were kept on a frictionless surface then would they slide away?{even if the effect is negligible, is it there?} Feb 15, 2017 at 4:43
• @HolgerFiedler. Same force does not at all imply same speed. Feb 15, 2017 at 5:27