well... I would say:
> a door
>A chair
>a table leg
at right angles to
They can, yes.
Generally not, though they can be.
Perpendicular means 'at right angles to'.
yes and then it will be called a right-angled triangle
Engine, wheels, driver, fuel and slope of the ground.
on the ground
A heptahedron is a closed 3-d shape with 7 polygonal faces. There are 34 topologically different convex heptahedra and, since none of these are regular, the term is ambiguous. Only the right pentagonal prism, a very special version of one of the 34 topological forms has 5 faces which are perprdicular to the other 2.
1 Ground = 5 Cents
No, not all things come from the ground. While many things do originate from the ground, such as plants and minerals, there are also substances and objects that come from other sources, such as the air, water, or manufactured materials.
Leave the poor things alone.
Perpendicular lines are lines that eventually intersect, and intersecting means when the run into eachother. For example, the "L" shape are two perpendicular lines because the lines run into eachother.