where 
is the displacement from the fixed point. A particle moving under the influence of such a force (and no other) will execute simple harmonic motion about the fixed point. [P5.1]
is: a force, directed towards a fixed point, that is linearly proportional to the displacement from that point and in the opposite direction to that displacement. [P5.1]
in one dimension may be written: where is the displacement from the fixed point. A particle moving under the influence of such a force (and no other) will execute simple harmonic motion about the fixed point. [P5.1]
Copyright 1997, The Open University