The blame has been pinned, squarely and often, on inadequate oversight of U.S. financial institutions, which created ever more complex and risky mortgage instruments, lured people to buy homes they could not afford, and brought the economy crashing to the ground.
Motion on the Earth does not take place in a vacuum. When one thing moves, it moves through or across another. When a wheel turns on an axle, the two surfaces rub against one another. This is called dry friction. Grease can be used to separate the solid metal parts, but this just reduces the problem to layers within the grease sliding past one another.
A reaction force is a force that acts in the opposite direction to an action force. Friction is the reaction force resulting from surface interaction and adhesion during sliding. Reaction forces and reaction moment are usually the result of the actions of applied forces. When reaction forces exceed action forces, structure failure can occur and may lead to fracture as well as corrosion.