PT245 HIP ABDUCTOR MUSCLE FORCE PROBLEM
Page 2
Free Body Diagram
The problem can be visualized as two forces (body
weight and hip abductor muscle force) and a rigid, horizontal bar or moment
arm (the pelvis). The forces are balanced on an axis (the hip joint). These
forces and the moment arm comprise a Class I lever system. The diagram
is not completely accurate because the direction of the hip abductor muscle
force is represented as being vertical. In fact, the hip abductor muscle
force is acting at an angle of 70 degrees relative to the horizontal (see
skeletal diagram on previous page). To solve the problem, we will need
to find the rotary component of the hip abductor muscle force. the
rotary component is that part of the hip abductor muscle force that is
acting perpendicular to the moment arm (i.e., vertical in this case).
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