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Mechanical Engineering

Mechanical Engineering is a branch of engineering that encompasses the generation and application of heat and mechanical power and the design, production, and use of machines and tools. Mechanical engineering involves application of the principles of dynamics, control, thermodynamics and heat transfer, fluid mechanics, strength of materials, materials science, electronics, and mathematics.

10,989 Questions

What is thermal conductivity of brass a?

The thermal conductivity of brass is around 109-130 W/mK, depending on the specific composition of the brass alloy. Brass is a good conductor of heat, making it useful in applications where heat transfer is important.

How does an electric kettle know to switch off when the water is boiling?

First, a 'Bi-metallic Strip' consisting of two different metals, having different 'Coefficients of Expansion', fused together in a two-layer strip which is connected electrically to the kettle element power supply.

It is placed in a chamber, generally in the kettle handle, where steam from the top of the kettle can come into contact with the chamber holding the metal strip. (Not with the strip itself).

When at room temp., the electrical contacts are closed allowing current to flow to the Element when power is switched on.

When the kettle boils, steam is passed around the chamber that contains the strip, causing it to heat up.

The metal having the higher 'C of E' of the two making up the bi-metal strip, will expand more than the other, causing the strip to bend and open the contacts, thus shutting off the power.

Are alloys genrally weaker of stronger the pure metals?

Alloys are generally stronger than pure metals because they combine the beneficial properties of different metals to create a material with enhanced mechanical and physical properties. The mixing of metals in an alloy can improve characteristics such as strength, hardness, and corrosion resistance, making them more desirable for many applications.

A weightlifter expends 294 W of power lifting a weight to a height of 2 m in 10 seconds What mass has he lifted?

To calculate the mass lifted, first calculate the work done using the formula Work = Power x Time. In this case, Work = 294 W x 10 s = 2940 J. Then, use the formula for work done against gravity, which is Work = Force x Distance. Substitute the values 2940 J for Work, 2 m for Distance, and 9.81 m/s^2 for acceleration due to gravity to find the Force (Weight). Finally, use the formula Weight = mass x gravity, where gravity is 9.81 m/s^2, to determine the mass lifted.

Definition of least count of screw gauge?

The least count of a screw gauge is the smallest measurement that can be read or determined using the instrument. It is essentially the smallest change in the position of the thimble that can be detected, which corresponds to the smallest change in the measured dimension.

How many kilowatts are there in 30000 btu?

This is a power unit conversion from British thermal units per hour (Btu/hr.) to its equivalent in horsepower (hp). There are 2544.43 btu/hr. in one horsepower. Conversely, there are 0.000393 hp in one Btu/hr.

What is the difference between pig iron and steel?

Pig iron is the initial form of iron produced during the smelting of iron ore, containing high carbon content and impurities. Steel is an alloy of iron that contains less carbon and is produced by further refining pig iron to remove impurities and control the carbon content, resulting in a more malleable and versatile material.

Are Alloys tough?

Yes, alloys are generally tough and strong because they are a combination of two or more metals. The unique combination of different metals in an alloy can enhance properties like hardness, strength, and durability, making them suitable for a wide range of applications.

What the difference between low alloy steels and high alloy steels?

The difference in classification of low alloy and high alloy steels is based on the metal composition: low alloy steels include a lower concentration of alloying metals versus high alloy steels. The composition affects properties like strength, ductility, etc.

Is a car a shell structure?

A car can be considered a shell structure, as the body of the car is designed to provide structural support and protection to the occupants. The body panels of the car generally act as a shell, distributing external forces across the frame to ensure structural integrity and safety.

How do you make a forcemeter out of household objects?

You can make a simple forcemeter using a spring scale, rubber bands, a wooden stick, and a hook. Attach the hook to the spring scale, then use rubber bands to connect the hook to the wooden stick. Apply force to the stick, and the spring scale will measure the force exerted.

Is post heating required for carbon steel material above 19.05mm thickness?

Post heating is generally recommended for carbon steel material above 19.05mm thickness to reduce the risk of cracking during welding and to promote better mechanical properties. The specific post-heating requirements may vary based on the material and welding process being used. It is best to consult the specific welding procedure specifications to determine the exact post-heating requirements for the application.

What does the term base or parent metal in an alloy mean?

The term "base metal" or "parent metal" in an alloy refers to the primary metal that forms the majority of the alloy's composition. It serves as the foundation of the alloy, with other elements added to enhance its properties. The base metal determines the alloy's primary characteristics and properties.

Which metal was often confused with lead and tin?

Zinc was often confused with lead and tin due to their similar appearances. However, zinc has a higher melting point than lead and tin, and it does not oxidize easily like lead and tin.

What is the difference between shielded and unshielded welding?

Shielded welding uses a shielding gas to protect the weld pool from contamination and oxidation, while unshielded welding does not use such gas and is typically done in a protected atmosphere like underwater or in a vacuum. Shielded welding produces cleaner and stronger welds due to the protection from atmospheric elements.

Type of thermodynamic properties?

Thermodynamic properties are specific volume, density, pressure, and temperature. Other properties are constant pressure, constant volume specific heats, Gibbs free energy, specific internal energy and enthalpy, and entropy.

What is H7 in hole dimension?

It a Standart for holes

Ex. DS 807 (Dansk Standart) v.3 Sep. 1992

Hole in mm and tolranc in µm (mikrometer)

0-3 mm = +10 to 0 µm = 3,000 to 3,010 = 3 H7

3-6 mm = +12 to 0 µm = 6,000 to 6,012 = 6 H7

6-10 mm = +15 to 0 µm = 10,000 to 10,015

10-18 mm = +18 to 0 µm = 18,000 to 18,018

18-30 mm = +21 to 0 µm = 30,000 to 30,021

30-50 mm = +25 to 0 µm = 50,000 to 50,025

50-80 mm = +30 to 0 µm = 80,000 to 80,030

80-120 mm = +35 to 0 µm = 120,000 to 120,035

120-180 mm = +40 to 0 µm = 180,000 to 180,040

180-250 mm = +46 to 0 µm = 250,000 to 250,046

250-315 mm = +52 to 0 µm = 315,000 to 315,052

315-400 mm = +57 to 0 µm = 400,000 to 400,057

400-500 mm = +63 to 0 µm = 500,000 to 500,063

OSV......

Ex. 15 mm H7 is 15,000 to 15,018 mm

Ex. 81 mm H7 is 81,000 to 81,035 mm

I don't know if the standart is the same everywhere :)

What is pressure compounding?

Pressure compounding is a method used in steam turbines to improve efficiency by dividing the pressure drop across multiple stages. This involves passing steam through a series of turbine stages, with each stage operating at a different pressure level. By reducing the pressure drop across each stage, pressure compounding helps to extract more energy from the steam and increase the overall turbine efficiency.

What instrument is used to predict wind speed?

A series of barometers can be used to predict wind speed and direction. Wind will move from higher pressure areas to lower pressure areas. The higher the pressure differential the higher the wind speed will be.

1.8N equals to how many kPa?

Depends on the surface it is applied: N is a unit of mass, kPa a unit of pressure. Divide 1.8 by the surface in square m, then by 1000 and you'll obtain the pressure you need in kPa.

Effects of carbon on the mechanical properties of iron alloy?

iron by itself is a very weak metal and it does not find any good use in the industrial applications. when carbon is added to iron as a solid solution it adds strength to it. this gives us the steel alloy. if you refer the iron-iron carbide equilibrium diagram then you will find it amazing how iron and carbon can exhibit different crystal structure this leads to the formation of a lot of variety of steel. steels can be heat treated from being very soft to being very hard and the opposite can be done as well. very tough steels can be made, very ductile steels can be made , very hard steels can be made , etc etc etc etc.,

Relation between power and discharge of a reciprocating pump?

The power required by a reciprocating pump is directly proportional to the discharge it produces. When the discharge increases, the power needed to maintain that flow rate also increases. This relationship is governed by the pump efficiency and the pressure head against which the pump is operating.

How is iron converted to steel?

Iron is converted to steel through a process called steelmaking, which typically involves melting the iron in a furnace and adding controlled amounts of carbon and other alloying elements to change its properties. This alters the composition and structure of the iron, resulting in the production of steel with desired characteristics such as strength, hardness, and ductility.

How much psig equal to 1 psi?

There is no mathematical conversion needed - 1 psi is equal to 1 psi. The terms "psig" and "psi" are often used interchangeably to refer to pounds per square inch of pressure. However, "psig" specifically denotes pressure relative to the local atmospheric pressure, while "psi" is an absolute measure.