Moments and levers

The turning effect of a force is called the [blank_start]moment[blank_end] of the force.

The [blank_start]moment[blank_end] of the force both depends on the size of the [blank_start]force[blank_end] and how far it is [blank_start]applied[blank_end] to the pivot or [blank_start]fulcrum[blank_end].

moment of force = [blank_start]force[blank_end] x [blank_start]perpendicular distance from fixed axis[blank_end]

The law of [blank_start]memoments[blank_end] (also called the law of the lever) is stated as follows: When a body is in equilibrium the [blank_start]sum[blank_end] of the clockwise moments about any [blank_start]point[blank_end] [blank_start]equals[blank_end] the sum of the [blank_start]anti-clockwise[blank_end] moments about the [blank_start]same[blank_end] point. There is no [blank_start]net[blank_end] moment on a body which is in equilibrium.

The unit for the moment of force is the [blank_start]newton metre[blank_end] ([blank_start]N m[blank_end]).

A [blank_start]level[blank_end] is any device which can turn about a [blank_start]pivot[blank_end]. In a working [blank_start]level[blank_end] a force called the [blank_start]effort[blank_end] is used to overcome a [blank_start]resisting[blank_end] force called the [blank_start]load[blank_end].

The conditions for equilibrium are: (i) The [blank_start]sum[blank_end] of the [blank_start]forces[blank_end] in one direction [blank_start]equals[blank_end] the sum of the forces in the [blank_start]opposite[blank_end] direction. (ii) The law of [blank_start]moments[blank_end] must apply.

According the [blank_start]first[blank_end] condition for equilibrium, the [blank_start]reactions[blank_end] have to [blank_start]equal[blank_end] each other.