As a person walks, the femur (upper leg bone) slides in a socket in the hip. This socket contains cartilage and synovial fluid, giving it a low coefficient of friction. Consider a 68kg person walking on a horizontal sidewalk. Typically, both legs together comprise 34.5% of a person's weight.
Part A Find the frictional force on the bone in the hip joint. Assume ? =0.003.
Part B If this person were walking on the Moon, where g = 1.67 m/s2, what would be the frictional force at the hip joint?
Part C With age or with osteoarthritis, the synovial fluid can dry up, resulting in a much higher coefficient of friction. If this coefficient increases 100-fold (which can happen), what would be the frictional force (on Earth)?