Centres of mass

A body behaves as if its whole mass were concentrated at one point.

Every body has a centre of [blank_start]mass[blank_end].

For a human, the centre of [blank_start]mass[blank_end] is somewhere in the [blank_start]midddle[blank_end] and the [blank_start]vertical[blank_end] line from it must be within the [blank_start]area[blank_end] enclosed by its [blank_start]feet[blank_end] or else it will [blank_start]fall[blank_end] over.

The [blank_start]centre[blank_end] of mass of a regulary [blank_start]shaped[blank_end] body that has the same [blank_start]density[blank_end] throughout is at its [blank_start]centre[blank_end]. In other cases it can be [blank_start]found[blank_end] by an [blank_start]experiment[blank_end].

When the vertical line of a body's centre of mass doesn't go through the area of the body, the body will topple over.

The [blank_start]stability[blank_end] of a body is [blank_start]increased[blank_end] by: (i) [blank_start]lowering[blank_end] its centre of mass, and (ii) [blank_start]increasing[blank_end] the area of its [blank_start]base[blank_end]

[blank_start]Unstable[blank_end] equilibrium is when a body moves [blank_start]further[blank_end] away from its [blank_start]previous[blank_end] position when it is slightly displaced and then released.

[blank_start]Neutral[blank_end] equilibrium is when a body [blank_start]stays[blank_end] in its [blank_start]new[blank_end] position when [blank_start]displaced[blank_end].

[blank_start]Stable[blank_end] equilibirum is when a body is slightly displaced and when it is released it [blank_start]returns[blank_end] to its [blank_start]previous[blank_end] position.