Finding the centroid of a shape like a circle or square is very easy. However for an object such as a beam, the centroid is only represented by the geometric center if the material is uniform or homogenous. Beams and other materials are often reinforced with a different material. Such reinforcement likely changes the location of the centroid from the geometric center. It is important that engineers account for this in their designs.
Activity 1.3.3
Think back to the last time someone complained about a door being left open. What did you notice about the temperature within the room as a result of the open door? In Activity 1.3.3 you will investigate the effects of work, thermal energy, and energy on a system, as in the case of the room with the door left open.
Activity 1.2.4
Regardless of circuit complexity, circuit designers as well as users need to be able to apply basic electrical theories to circuits in order to verify safe operation and troubleshoot unexpected circuit failure. In this activity you will gain experience applying Ohm’s law and Kirchhoff’s voltage and current laws to circuits in order to gain understanding of circuit requirements and relationships between voltage, current, and resistance.
Activity 1.1.3
You do not have to look far to see gears. You might not think of an object such as a computer as having a lot of moving parts, but the CD tray on your computer is likely controlled by gears. A traditional watch is full of gears. The watch has one source of power or input that must move multiple hands continuously and at different speeds. Some watches also keep track of the day of the month. This may be low-tech by today’s standards, but imagine the challenge of choosing just the right gears to keep a watch synchronized. In a watch the gears are used to manipulate rotational speed. Gears are also used in many applications to control torque and rotational direction.
Activity 2.1.2
Engineers must look for better ways to build structures. Less material typically means that structures will be lighter and less expensive. Knowing the moment of inertia for different shapes is an important consideration for engineers as they strive to make designs lighter and less expensive.
Activity 1.2.1
According to the United States Department of Energy, Americans spend 500 billion dollars each year on energy. The world is facing the challenge of significantly increasing energy needs. Many unique energy sources are available. To meet future energy needs, engineers need to design technology to contribute new ways to harness energy, increase efficiency, and better transport and store energy.
Activity 1.1.4
Pulleys and sprockets achieve the same tasks as gears by transferring power through rotary motion. Depending on how pulleys and sprockets are applied, speed, direction, and torque can be modified within the system. Pulleys and sprockets are both used in everyday machines ranging from industrial applications to moving printer heads within a desktop printer. Typically, belts and pulleys are easier to manufacture, lighter weight, and less expensive to purchase than sprockets and chains. Although chains and sprockets are more difficult to manufacture and often noisier, they have the advantage of not slipping as easily and tend to be more durable then a belt and pulley system.
Activity 2.1.3
In 1981 at a Kansas City Hyatt, a walkway holding hundreds of people collapsed during a party. The collapse killed 114 people and injured 200 others. When building this walkway, designers and engineers made serious errors that allowed the collapse to occur under the weight of so many people. In such a design, every part must be analyzed to ensure that it can perform its intended function without failing. One planning tool that engineers can use is the free body diagram. Free body diagrams show all forces that act upon a body or part. The information identified in a free body diagram can be used to determine whether a part is adequate.
Activity 1.2.3
Since the late 1800s, engineers have designed systems to utilize electrical energy due to its ability to be converted, stored, transmitted, and reconverted efficiently into other forms of energy. In the 21st century, electrical energy production, distribution, and application have become consumer driven. Today’s consumer utilizes electrical energy in all aspects of life, from cell phones and computers to refrigeration and heating and cooling systems, and even transportation. Electrical energy, depending on geographic location, is converted from mechanical energy, chemical energy, light energy, and thermo energy before it reaches the consumer.
Regardless of the conversion process, electrical energy consists of three basic components: current, voltage, and resistance. Current is the net transfer of electric charge per unit of time. Voltage is the amount of work required to move a charge from one point to another. Resistance is the opposition to the flow of current. Understanding the relationship between current, voltage, and resistance allows engineers to design efficient, safe, and functional electrical circuits. Electrical circuits consist of the following components: an energy source to provide voltage, conductors to allow current travel, insulators to limit current travel, and a load. Electrical circuits provide an uninterrupted path for current travel and are broken into two distinct categories of design: series circuits and parallel circuits.
Activity 1.1.5
Answer the following questions regarding gear, pulley, and sprocket systems. Each question requires proper illustration and annotation including labeling of forces, distances, direction, and unknown values. Illustrations should consist of basic top view assembly sketches rather than realistic pictorials. Be sure to document all solution steps and proper units. Remember: counted teeth have infinite digits, and assume all other measurements contain three (3) significant digits.
All problem calculations should assume ideal conditions and no friction loss.