Question Set 137

· What is mechanism?

A mechanism is an assembly of different parts which perform a complete motion and is often part of a machine.

· State Newton's three laws of Motion.

- The law of inertia: Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
- Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). Force=Mass times acceleration.
- For every action there is an equal and opposite reaction.

· State the laws of thermodynamics and its importance of in Mechanical Engineering.

Thermodynamics is a physical science which studies the interrelation between heat, work and the internal energy of any system. Thermodynamics helps study all the systems of mechanical engineering. There are three laws of thermodynamics.

First Law: Energy can be neither created nor destroyed. It can only change forms. In any process in an isolated system, the total energy remains the same.

Eg: turning on a light would seem to produce energy; however, it is electrical energy that is converted.

Second Law: The second law of thermodynamics states that the entropy of any isolated system not in thermal equilibrium almost always increases.

Eg: A car that has run out of gas will not run again until you walk 10 miles to a gas station and refuel the car.

Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.

Eg: Water in gas form has molecules that can move around very freely. Water vapor has very high entropy (randomness). As the gas cools, it becomes liquid which can still move around but not as freely. At this point they have lost some entropy. On cooling further it becomes solid ice where molecules can no longer move freely but can only vibrate within the ice crystals. The entropy is now very low. As the water nears absolute zero, the vibration of the molecules diminishes. If the solid water reaches absolute zero, all molecular motion would stop completely. And at this point the water would have no entropy at all.

· What is Hess law?

According to the Hess law the energy transfer is simply independent of the way being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.

· What is PS?

Personal Statement. It is something that gives an informative background about an individual.

· What is a bearing? What are the different types of bearings?

Bearing is a device that helps smoother movement with minimal friction which in turn helps enhances efficiency and speed. Considering two types of loading, radial and thrust, there are different types of bearings which help handle these loads. The basic difference in the types of loads is essentially due to their ability to handle weight and different kinds of loads for various applications. Different types of bearings are:

-Ball bearing
-Roller bearing
-Ball Thrust bearing
-Roller thrust bearing
-Tapered roller bearing
-Magnetic bearings
-Giant Roller Bearing

· What is a process flow diagram?

A Process Flow Diagram is a user friendly, simplified sketch which illustrates general plant streams, major equipments and key central loops and shows the relationship between major components in the system. By using symbols to identify instruments and vessels it describes the primary flow course. They also provide e detail of mass/energy balance data along with stream composition and physical properties, however do not show minor components.

· What is a time and motion theory?

Frederick Taylor was pioneer of the time and motion theory. This technique monitors the amount of time required to complete a task along with observing the steps taken by a worker to complete the given task.

· Which is the hardest material on earth?

Diamond is currently the hardest material, made up of carbon atoms which cannot move. Carbon is the only atom that can have four electrons in the second shell surrounding the carbon nucleus, precisely why making a diamond the hardest material. However, there also are claims by a few to a new rare material called Wurtzite Boron Nitride which has a structure similar to a diamond but has some other atoms in place of carbon.