1. Forging new generations of engineers

2. Properties of Geometric Solids
Calculating Volume, Weight, and Surface Area

3. Properties of Geometric Solids
Introduction to Engineering Design TM
Unit 1 – Lesson 1.4 – Geometric Shapes and Solids
Geometric Solids
Solids are three-dimensional objects.
In sketching, two-dimensional shapes are used to create the illusion of three-dimensional solids.
Identify the Shapes in all pictures
Project Lead The Way, Inc.
Copyright 2007

4. Properties of Solids
Volume, mass, weight, density, and surface area are properties that all solids possess. These properties are used by engineers and manufacturers to determine material type, cost, and other factors associated with the design of objects.

5. Volume
Volume (V) refers to the amount of space occupied by an object or enclosed within a container.
Metric English System
cubic cubic inch
centimeter
(cc)
(in3)

6. Volume of a Cube V = s3 A cube has sides (s) of equal length.
The formula for calculating the volume (V) of a cube is:
V = s3
V= s3
V= 4 in x 4 in x 4 in
V = 64 in3

7. Volume of a Rectangular Prism
A rectangular prism has at least one side that is different in length from the other two.
The sides are identified as width (w), depth (d), and height (h).

8. V = wdh Volume of a Rectangular Prism
The formula for calculating the volume (V) of a rectangular prism is:
V = wdh
V= wdh
V= 4 in x 5.25 in x 2.5 in
V = 52.5 in3

9. Volume of a Cylinder
To calculate the volume of a cylinder, its radius (r) and height (h) must be known.
The formula for calculating the volume (V) of a cylinder is:
V = r2h
V= r2h
V= 3.14 x (1.5 in)2 x 6 in
V = in3

10. Mass
Mass (M) refers to the quantity of matter in an object. It is often confused with the concept of weight in the metric system.
Metric English System
gram slug
(g)

11. Weight
Weight (W) is the force of gravity acting on an object. It is often confused with the concept of mass in the English system.
Metric English System
Newton pound
(N) (lb)

12. Mass vs. Weight
Contrary to popular practice, the terms mass and weight are not interchangeable, and do not represent the same concept.
W = Mg
weight = mass x acceleration due to gravity
(lbs)
(slugs)
(ft/sec2)
g = ft/sec2

13. Mass vs. Weight
An object, whether on the surface of the earth, in orbit, or on the surface of the moon, still has the same mass.
However, the weight of the same object will be different in all three instances, because the magnitude of gravity is different.

14. Mass vs. Weight
Each measurement system has fallen prey to erroneous cultural practices.
In the metric system, a person’s weight is typically recorded in kilograms, when it should be recorded in Newtons.
In the English system, an object’s mass is typically recorded in pounds, when it should be recorded in slugs.

15. Weight Density
Weight density (WD) is an object’s weight per unit volume.
English System
pounds per cubic inch
(lbs/in3)

16. Weight Density Substance Weight Density Water Freshwater Seawater
Gasoline
Aluminum
Machinable Wax
Haydite Concrete
.036 lb/in3
.039 lb/in3
.024 lb/in3
.098 lb/in3
.034 lb/in3
.058 lb/in3

17. Calculating Weight
To calculate the weight (W) of any solid, its volume (V) and weight density (Dw) must be known.
W = VDw
W = VDw
W = in3 x .098 lbs/in3
W = 3.6 lbs

18. Area vs. Surface Area
There is a distinction between area (A) and surface area (SA).
Area describes the measure of the two-dimensional space enclosed by a shape.
Surface area is the sum of all the areas of the faces of a three-dimensional solid.

19. Surface Area Calculations
In order to calculate the surface area (SA) of a cube, the area (A) of any one of its faces must be known.
The formula for calculating the surface area (SA) of a cube is:
SA = 6A
SA = 6A
SA = 6 x (4 in x 4 in)
SA = 96 in2

20. Surface Area Calculations
In order to calculate the surface area (SA) of a rectangular prism, the area (A) of the three different faces must be known.
SA = 2(wd + wh + dh)
SA = 2(wd + wh + dh)
SA = 2 x in2
SA = in2

21. Surface Area Calculations
In order to calculate the surface area (SA) of a cylinder, the area of the curved face, and the combined area of the circular faces must be known.
SA = (2r)h + 2(r2)
SA = 2(r)h + 2(r2)
SA = in in2
SA = in2