Answer all of both $($a$)$ and $($b$)$ below.

$($a$)$ Briefly state what Gravitational Mass and Inertial Mass are, and briefly state the

principle of equivalence. $10\%$ of question weight.

$($b$)$ Explain the interplay between the position of the centre of body mass and forces

controlling postural sway in normal standing.

Refer in your discussion to the $5$ conditions given in David Winter$$s line drawing of

postural sway

In each of the $5$ conditions, briefly state how plantar$-$flexor muscle activation is

contributing to controlling the sway, and their influence on the position of the force$-$

couple caused by the position of the ground reaction force vector $($R$)$ relative to the

position of the line of gravity $($LoG$)$; state that force$-$couple$$s turning effect

$($moment$)$ and how that is altering the angular acceleration $($$),$ angular velocity $($$)$

and angular momentum $($L$)$ of the body $(90\%$ of question weight$)$