# Unit 5 Geometry of Design

## 35 terms · Terms for Unit 5 Geometry of Design - PLTW

### acute triangle

A triangle that contains only angles that are less than 90 degrees.

### angle

The amount of rotation needed to bring one line or plane into coincidence with another, generally measured in radians or degrees.

### area

The number of square units required to cover a surface.

### axis

1. An imaginary line through a body, about which it rotates.
2. An imaginary line about which a regular figure is symmetrically arranged.
3. A fixed reference line for the measurement of coordinates.

### center of gravity

A 3D point where the total weight of the body may be considered to be concentrated.

### centroid

A 3D point defining the geometric center of a solid.

### circle

A round plane figure whose boundary consists of points equidistant from the center

### circumscribe

1. A triangle located round a polygon such as a circle.
2 To draw a figure around another, touching it at points but not cutting it.

### cylinder

A solid composed of two congruent circles in parallel planes, their interiors, and all the line segments parallel to the axis with endpoints on the two circles.

### density

The measure of mass density is a measure of mass per volume.

### diameter

A straight line passing from side to side through the center of a circle or sphere.

### ellipse

A shape generated by a point moving in a plane so that the sum of its distances from two other points (the foci) is constant and equal to the major axis

### fillet

A curve formed at the interior intersection between two or more surfaces.

### inscribe

To draw a figure within another so that their boundaries touch but do not intersect.

### mass

The amount of matter in an object or the quantity of the inertia of the object.

### meniscus

The curved upper surface of a liquid column that is concave when the containing walls are wetted by the liquid and convex when not.

### obtuse triangle

A triangle with one angle that is greater than 90 degrees.

### parallelogram

A four-sided polygon with both pairs of opposite sides parallel.

### pi (π)

The numerical value of the ratio of the circumference of a circle to its diameter of approximately 3.14159.

### polygon

Any plane figure bounded by straight lines.

### principal axes

The lines of intersection created from three mutually perpendicular planes, with the three planes' point of intersection at the centroid of the part.

### prism

A solid geometric figure whose two ends are similar, equal, and parallel rectilinear figures, and whose sides are parallelograms.

A four-sided polygon.

A straight line from the center to the circumference of a circle or sphere.

### rectangle

A parallelogram with 90 degree angles. A square is also a rectangle.

### regular polygon

A polygon with equal angles and equal sides.

### right triangle

A triangle that has a 90 degree angle.

### round

Two or more exterior surfaces rounded at their intersections.

### square

A regular polygon with four equal sides and four 90 degree angles.

### surface area

The squared dimensions of the exterior surface.

### tangent

A straight or curved line that intersects a circle or arc at one point only.

### title block

A table located in the bottom right-hand corner of an engineering drawing that identifies, in an organized way, all of the necessary information that is not given on the drawing itself. Also referred to as a title strip.

### triangle

A polygon with three sides.

### vertex

Each angular point of a polygon, polyhedron, or other figure.

### volume

The amount of three-dimensional space occupied by an object or enclosed within a container.