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.
Friction. Friction is a resistance to motion that is opposite the direction of travel. It is caused when two surfaces are in contact. Since friction acts to slow down a moving object, it is called a resistive force. This is different than active forces that cause objects to accelerate or change direction. Friction is mainly caused by surface roughness. The classic law of friction states that friction is the product of a coefficient and a force.