Total knee replacement is one of the most successful procedures in all of medicine. In the vast majority of cases, it enables people to live richer, more active lives free of chronic knee pain. Over time, however, a knee replacement may fail for a variety of reasons.
Resistance movement. A resistance movement is an organized effort by some portion of the civil population of a country to resist the legally established government or an occupying power and to disrupt civil order and stability.
Air resistance force is the force of air pushing against a moving object. Air resistance force is a type of frictional force (refer to Chapter 5 of this unit). Like all frictional forces, the force of air resistance always opposes the motion of an object. Usually, the air resistance force is not very strong. When you walk, for example, you are affected by air resistance force, but it does not really slow you down.