Define the moment of a force about a point.
Determine the SI base units of the moment of a force.
A uniform rigid rod of length 
is shown in the figure below.
The rod has a weight of 
and is made of wood of density 
. Calculate the cross-sectional area 
, in 
, of the rod.
A fishing rod AB, made from the rod in (b), is shown in the figure below.
End A of the rod rests on the ground and a string is attached to the other end B. A support stick exerts a force perpendicular to the rod at point C. The weight of the rod acts at point D. The tension 
in the string is in a direction perpendicular to the rod. The rod is in equilibrium and inclined at an angle of 
to the vertical.
Show that the component of the weight that is perpendicular to the rod is 
.
By taking moments about end A of the rod, calculate the tension .
and the perpendicular distance 
of the line of action of the force from the point.
.
