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.
Context: When two surfaces are in contact, friction is always present. Definition: To pull along with difficulty or effort. Context: An airplane comes to a stop because of the drag or pull on it as it moves through air and across a surface. Definition: Strength or energy exerted. Context: A force can change the direction of motion, increase the rate of motion, slow down motion, or stop it all together. Definition: The rubbing of one object or surface against another; the force that resists motion between bodies in contact. Context: Bicycle brakes use friction to stop the wheels from turning.