How many types of goal posts are there in football, and what materials are used to construct them? What are the dimensions of the goals?
According to FIFA's Laws of the game PDF
The size of the goalpost is 7.32 m (8 yds) x 2.44 m (8 ft).
The distance between the posts is 7.32 m (8 yds) and the distance from the lower edge of the crossbar to the ground is 2.44 m (8 ft).
Other characteristics (taken from the same law):
A goal consists of two upright posts equidistant from the corner ﬂagposts and joined at the top by a horizontal crossbar. The goalposts and crossbar must be made of wood, metal or other approved material. They must be square, rectangular, round or elliptical in shape and must not be dangerous to players.