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 does not only stop objects from moving. It also causes objects to heat up or make a sound. When you rub your hands together, for example, they begin to feel warmer because friction is heating them up. In addition, rubbing your hands together makes a sound. There are three main types of friction: sliding friction, rolling friction and fluid friction.