Mechanical Minds

# Mechanical Minds

A blog for complete information about Mechanical Engineering.

## ALL YOU NEED TO KNOW ABOUT UNIT AND UNIT CONVERSION !!

May 23, 2018

unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity.For example, a length is a physical quantity. The metre is a unit of length that represents a definite predetermined length. When we say 10 metres (or 10 m), we actually mean 10 times the definite predetermined length called "metre".

## DIFFERENCE BETWEEN ALIGNMENT AND BALANCING EXPLAINED !!

May 19, 2018
Alignment and balancing are two words that we hear too often whenever we go for a servicing of our car but very few understand the difference between the two. These are closely related concepts that make sure that you are safe while driving and do not face a mishap on road because of faulty alignment of tires or if the balancing of tires is not perfect. Let us clarify the two concepts so you know what you need when there is any trouble with the wheels of your car.

### Balancing

Balancing is necessary as with constant rotation, tire becomes unbalanced. Out of balance tires cause vibration of the vehicle, and at higher speeds, the risk of a mishap greatly increases. Balancing of tires is therefore imperative after every 12-15 thousand miles of run. Balancing also ensures that your tires have a longer life as wear of tires is greatly reduced with balancing.

### Alignment

All tires of a new car are perfectly aligned which means that they all point in one direction. This ensures that no tire unduly pushes out or pulls inward causing trouble for the vehicle. If the wheels are perfectly aligned the tires not only have a longer life, you also get better mileage. This also eases pressure on the suspension of the automobile, and in general gives more driving pleasure.

### Difference between Alignment and Balancing

Though balancing and alignment are different, they have a bearing on the state of the car which is low mileage and an increased probability of a mishap. Wheel balancing is done on an automated machine which corrects minor imbalances of wheel assembly. On the other hand wheel alignment is a process that ensures that angles of caster, camber and toe are correct. In simple words, it makes the tires point in a single direction.

### In brief:

• Alignment and balancing are important for your safety and wear of the tires of your car
• Balancing corrects any imbalance of tires or wheels while alignment ensures that your wheels point in the same direction
• If both wheel balancing and alignment are regularly done, tires have a longer life and you get more mileage from your car

May 17, 2018

## Thursday, 10 May 2018

May 10, 2018

Suppose you are driving home from a weekend vacation. It's late at night, and the winding two-lane road has no streetlights. You approach a curve at 40 mph -- slow enough to make the turn, but too fast to stop suddenly if you need to.
In this case what would you do ?

One option is to slow down your vehicle and look what is in front as headlights are focusing in straight line.

A car with adaptive headlights uses electronic sensors to detect the speed of the car, how far the driver has turned the steering wheel, and the yaw of the car. Yaw is the rotation of the car around the vertical axis -- when a car is spinning, for example, its yaw is changing. The sensors direct small electric motors built into the headlight casing to turn the headlights. A typical adaptive headlight can turn the lights up to 15 degrees from center, giving them a 30-degree range of movement.

## INTERVIEW QUESTIONS OF THERMODYNAMICS !!!

May 09, 2018
1.Why Entropy decreases with increase in temperature?
Ans: ds=dQ/T. Entropy is inversely proportional to the temperature so, as temp. Increases, entropy decreases.

2.What is the difference between heat transfer and thermodynamics?
Ans: Heat transfer deals with the energy analysis which in transition and and depends on the modes of heat transfer like conduction, convection and radiation or combination of any modes. Heat transfer deals in non equilibrium domain and conditions while thermodynamics deals with study of system at equilibrium and does not depend on how heat transfer is calculated.

3.When a real gas behaves like ideal gas?
Ans:A real gas behaves like an ideal gas in low pressure and high temperature conditions.

4.What is Hess Law?
Ans:According to the Hess law the energy transfer is simply independent of the path 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.

5.What do you understand by latent heat? Give examples of latent      heat.
Ans:For pure substances, the heat effects accompanying changes in state at constant pressure (no temperature change being evident) are known as latent heats. Examples of latent heats are the heat of fusion, vaporization, sublimation and change in crystal form.

6.What is the difference between heat capacity and specific heat of the material?
Ans:The heat capacity of material is the amount of heat transformed to raise unit mass of a material 1° in temperature.
The specific heat of material is the ratio of the amount of heat transferred to raise unit mass of a material 1° in temperature to that required raise unit mass of water 1° of temperature at some specified temperature.

For most of the engineering purposes, heat capacities may be assumed numerically equal to specific heat values.

## 7.Why gas containers are mostly in a cylindrical shape?

Ans:The ideal shape would be a sphere. The container must have the capacity to withstand the extremely high pressure of liquefied gas. A spherical shape helps in distributing these forces uniformly.

8.Explain why re-heater is used in gas turbine?
Ans:
The advantage of reheater is that it significantly increases the thrust; which is a prime reason for its use in gas turbines.

## MANUAL VS AUTOMATIC TRANSMISSION : WHICH ONE IS BEST ??

May 07, 2018
Let us first understand what is manual and automatic transmission and then we can proceed with the comparison.

### What is Manual Transmission ?

Manual transmission cars are the cars that allow the driver to change the gears as per driving needs and there is a manual clutch pedal used while changing gears. The clutch uses solid clutch plate and pressure plate mechanism.

### What is Automatic Transmission ?

Automatic transmission on the other hand works automatically depending on the vehicle speed and engine speed. In automatic transmission cars, there is no clutch pedal, and clutch-plate mechanism is replaced with a hydraulic torque converter.

### Manual Transmission:

• Initial cost of manual transmission cars is low.
• Fuel Efficiency of Manual transmission is higher because of low energy loss of a clutch plate based system.
• Preventive maintenance  cost for Manual transmission is slightly lower.
• Breakdown maintenance cost of  manual transmission car due to lesser complex systems.
• Manual transmission is usually more sporty compared to automatic transmission.
• Manual transmission is less comfortable in city conditions due to changing of gears in traffic.
• It requires more skills to drive a manual transmission car as there has to be a coordination between speed and gears.

### Automatic Transmission:

• Initial cost of automatic transmission car is higher.
• Fuel Efficiency of Automatic transmission car is lower because of energy losses in hydraulic torque converter are higher.
• Preventive maintenance cost for automatic transmission car is slightly higher.
• Breakdown maintenance cost of  automatic transmission car is higher due to complex system.
• The driver does not have full liberty to choose what gears  he/she wants to drive in, thus it is less sporty as compared to the manual transmission.
• Automatic transmission is very comfortable as the driver needs not worry about the clutch and there is no need to manually change the gears with changing speeds. This adds a lots of convenience in city traffic.
• It requires lesser skills to drive an automatic transmission car compared to manual transmission car.

Basically, automatic transmissions are easier to use and more comfortable for the driver, while manual transmission vehicles are less expensive and more involved.

Comment in the section below,which is best according to you.

## WHY CONCRETE NEED REINFORCEMENT ??

May 04, 2018
Reinforced concrete is mostly used for construction on a large scale due to its desirable mechanical properties. Reinforced concrete, or RCC, is concrete that contains embedded steel bars, plates, or fibers that strengthen the material.

### Why concrete is reinforced??

Concrete can be very strong when it comes to absorbing stress in the form of compression. However, it does not perform well against tensile strength and crumbles when up against forces that tries to pull it apart. Concrete always experiences both kinds of stress in construction and if weight is put on the concrete beam from the top, it will hold up but deforms when it experiences tensile stress.
Reinforced materials are embedded in the concrete in such a way that the two materials resist the applied forces together.Concrete consists of a cement and stone aggregate mixture that forms a rigid structure with the addition of water. When steel that has a high tensile strength is embedded in concrete, the composite material withstands compression, bending, and tensile stresses. Such a material can be used for making any size and shape, for utilization in the construction.
The main quality of reinforced concrete is similarity of its coefficient of thermal expansion with that of steel, due to which the internal stresses initiated due to variation in thermal expansion or contraction are eliminated.