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Concepts of Engineering Midterm Study Guide

Questions

1.       Advantages of Pneumatics over Hydraulics

·         Pneumatic powered equipment is more suitable, particularly in industries where the factory units are plumbed for compressed air.

·         Hydraulics means use of pressurized fluids to execute a mechanical task.

·         Commonly seen hydraulics based equipment types are hydraulic presses, hydraulic hoppers, hydraulic cylinders, and hydraulic rams.

·         In order to affect mechanical motion, pneumatics employs compression of gases, based on the working principles of fluid dynamics in the concept of pressure.

·         Any equipment employing pneumatics uses an interconnecting set of components: a pneumatic circuit consisting of active components such as gas compressor, transition lines, air tanks, hoses, open atmosphere, and passive components.

2.       Chapter 18 

·         Resistance means to oppose forward movement.

·         Jet airplanes, fireworks, and recoil guns apply to the concepts of Newton’s third law.

·         Newton’s third law says every action has an equal and opposite reaction. This explains why thrusters will propel the spacecraft into outer space by pushing hot gases out a very high velocity. According to Newton's third law, the spacecraft will experience an equal and opposite force, propelling it upward into space. Also, acceleration of the games times their mass equals the acceleration of the rocket times its mass.

3.       Chapter 19 

·         The main difference between the two types of engines is in the way that they ignite the gas-air mixture. Gasoline engines take in a mixture of gas and air, compress it, and then ignite it with a spark plug. Diesel engines take in just air, compress it, and then inject fuel into the compressed air. The air is compressed enough to raise its temperature sufficiently so that the injected fuel will ignite it.

·         Diesel engines are more powerful, and therefore are used to power trains, cargo ships, and other heavy vehicles. Diesel engine exhaust contains more soot and other particulate pollutants than gasoline engines.

·         Volume, temperature, and pressure are related by the equation "Pressure (P) is proportional to the temperature (T) of the gas, divided by the volume (V) of the chamber.”

·         To determine the force with which the piston pushes the air during the second step of the diesel cycle, you would need to determine the pressure in the chamber and the surface area of the piston. P=F/A, therefore F= A x P. Y

·         Hybrid vehicles have both gas engines, and electric motors and batteries, so they can use both energy sources, either one at a time or together. Hybrid vehicles capture energy from braking to generate electricity and charge the batteries. Solar - powered vehicles use photovoltaic (solar) cells; hydrogen-powered vehicles are reenergized with hydrogen gas, or are powered by fuel cells.

4.       Inside the Teenage Brain 

·         Some say these sleep debts can have a powerful effect on a teen's ability to learn and retain new material -- especially abstract concepts like physics, math, and calculus.

·         Even though the public perception is about building bigger and better brains, what the research shows is that it's the relationships, it's the connections, and it’s the people in children's lives who make the biggest difference."

·         Sleep affects memory and learning of the teenage brain.

5.        Chapter 20 

·         According to an article in a financial journal, a certain company earned 3.85 million dollars last year. Based on this report of the company's yearly earnings, a person reading the article estimates that the company earned an average of approximately 30 thousand dollars per month. One way to solve this problem is to divide 3.85 million dollars by 12 months. Write 3.85 million as 3,850,000. Since the number of dollars will be divided by 12 and the question is asking for an estimate, use compatible numbers to estimate 3,850,000 as 3,600,000, which divides evenly by 12: 3,600,000 dollars divided by 12 months equals 300,000 dollars per month. Hence, 30 thousand dollars per month is too low by a factor of 10.

·         In a Stirling engine, the working gas never leaves the engine. A combustion engine is an open pneumatic system - air and fuel vapor enter the chamber on every cycle, are burnt, then are forced out into the open air.

·         Edmodo is a social networking website and learning management system for teachers, students, and parents. It is marketed as the Facebook for schools.

·         Because the working fluid remains inside the engine, the Stirling engine is considered a closed system. Only energy crosses the system boundary.

·         The engine for the wheelchair had to be quiet and had to deliver a lot of power. Because the Stirling engine is an external combustion engine, there are no explosions inside of the combustion chamber. Therefore, the engine is very quiet.