101⟩ What is the weight of 1m3 of seawater?
1 m^3 = 1000 lits
And 1 lit = 1 kg (approx)
Therefore 1 m^3 = 1000 kg (approx)
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164 Mechanical Engineering Questions And Answers
102⟩ In 1983 what changed about the length of the meter?
The French were the first to define the length of a meter by using an alluminium/platinum alloy bar of a meter length at 25 degrees Celsius. This however is very inaccurate for quantum measurements, as the length of the bar would change two much depending on how you hold it. A better measurement found in 1983 is the distance that light travels in a vacuum in 1/229,792,458ths of a second. (For those of us with a decent knowledge of relativity that measurement is taken in the rest frame). Crazy I know but at least this way any body in a good physics lab can reproduce this distance without the use of some silly French rod.
103⟩ What is an ortographic drawing?
Orthographic projections are views of a 3D object, showing 3 faces of it. The 3 drawings are aligned so that if the page were folded, it would create part of the shape. It is also called multiview projections.
The 3 faces of an object consist of its plan view, front view and side view. There are 2 types of orthographic projection, which are 1st angle projection and 3rd angle projection.
104⟩ What is the Density of plastic?
Plastics are the general term for a wide range of synthetic or semisynthetic polymerization products. There are many different plastics; all have their own density!
Most common plastics, however, have a density between .035 and .045 lb/cu in.
105⟩ What are different types of gate valves?
There are a few different designs:
Parallel disk gate valves use two disks with a spring in between them, sliding into the seats. At low pressure, the spring forces the disks outward against the seats, sealing off the valve. At high pressure, all the sealing is accomplished by the downstream disk.
Wedge gate valves use a tapered disk that slides into two seats set at a slight, converging angle. The wedging action provides the sealing force between the disk and the seat.
Single disk gate valves are used where the flow is always one-way (like sluices on dams). There is some flexibility in the attachment of the disk to the stem, so the differential pressure on the disk pushes it against the seat, sealing it off.
106⟩ Do you need to be an apprentice for mechanical engineering?
Most engineering jobs require at least a 4-year engineering degree. Since much of being an engineer is learned "on the job" it is good to have an internship or co-operative experience while in school, but it is not required for all engineering programs (some colleges do require it). You can get a job without an internship or co-op, but you should plan to "wow" them at your interview! It is always a good idea to get involved with engineering projects outside of the educational program, such as research or an engineering club. This shows employers that you have had some experience in a real working environment.
107⟩ Is there a metal that does not contain iron?
Most commercially available aluminum contains some other materials, but only accidental traces of iron, if any. For example, Copper, silver, and gold, same story.
108⟩ What type of paper when made into a paper boat floats longest?
I would use wax paper because of all the different kinds of paper it is the least absorbant.
109⟩ How can you convert air mass to air volume?
Mass = density * volume.
Air density is p/RT, where R is the gas constant for air (287 J/kg-K), T is the absolute temperature, and p is the pressure, equal to 101325 Pa at sea level.
At sea level and room temperature, the density of air is
rho 101325 N/m2/ (287 N-m/ (kg-K)*293 K
or about a) 2 kg/mc)
110⟩ What is the history on the invention of paper?
Paper was invented in Egypt and was originally made from papyrus.
111⟩ What is representative elementary volume?
Smallest volume over which measurements can be made that will yield a representative of the whole.
112⟩ How do concrete pumps work?
I wonder how concrete pumps work, liquid (fluid) concrete has a big viscosity, how the pump overcomes this big viscosity. I witnessed many times every couple seconds maybe 4-5 seconds the machine emits a loud thump. I think that sound come from pnomatic part of the machine.
113⟩ Which is first stress or strain?
They are different measurements of a material under a load.
Stress is the amount of Force per area. If you pull on a bar that has an area of 1/2 square inches with a 5000 pound force then the Stress would be the Force divided by the Area or
Stress = 5000 LB /divided by/ 1/2 In2 = 10,000 Pounds per Sq Inch (psi)
Strain is the measurement of the deflection of a material under a load. This measurement is very small and it is described in terms of Inches of deflection per the original length in Inches of the part.
Strain is measured as In/In. Under a given load, the stress will be present and the part will deflect. The chair you are sitting in has deflected ever so slightly while carrying your weight.
114⟩ Where do railway steam engines carry there water?
In the large tank on the front of the engine
115⟩ What is wet corrosion and galvanic corrosion?
Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially when in electrical contact with a different type of metal and both metals are immersed in an electrolyte.
When two or more different sorts of metal come into contact in the presence of an electrolyte, a galvanic couple is set up as different metals have different electrode potentials. The electrolyte provides a means for ion migration whereby metallic ions can move from the anode to the cathode. This leads to the anodic metal corroding more quickly than it otherwise would; the corrosion of the cathodic metal is retarded even to the point of stopping. The presence of electrolyte and a conducting path between the metals may cause corrosion where otherwise neither metal alone would have corroded.
Wet Corrosion: The main feature of corrosion of a divalent metal M in an aqueous solution containing oxygen is because of the corrosion process consists of an anodic and a cathodic reaction. In the anodic reaction (oxidation), the metal is dissolved and transferred to the solution as ions M2+. The cathodic reaction in the example is reduction of oxygen. It is seen that the process makes an electrical circuit without any accumulation of charges.
The electrons released by the anodic reaction are conducted through the metal to the cathodic area where they are consumed in the cathodic reaction. A necessary condition for such a corrosion process is that the environment is a conducting liquid (an electrolyte) that is in contact with the metal. The electrical circuit is closed by ion conduction through the electrolyte. In accordance with the conditions, this dissolution process is called wet corrosion, and the mechanism is typically electrochemical.
116⟩ How does an equal-arm balance work?
Two pans of equal balances are placed at the end of the beam, one at each end. A long pointer attached at right angles to the beam at the point of support. Zero on a scale indicates the beam is at rest.
117⟩ Why do you need a keyway in the construction of a wall?
A keyway is found in a wall made of concrete where there is two separate pours, which abut themselves, otherwise referred to as a cold joint. It makes sense to insert a concave keyway continuously along the length and in the center of a section of the first wall section poured to receive an abutting concrete pour later. This inserted keyway creates an interlocking style effect between the two abutting pours, which creates a higher quality connection than simply butting the two pours with nothing to interconnect them.
Typically, a keyway is found in a wall made of concrete where there is two separate pours, which abut themselves, otherwise referred to as a cold joint. It makes sense to insert a concave keyway continuously along the length and in the center of a section of the first wall section poured to receive an abutting concrete pour later. This inserted keyway creates an interlocking style effect between the two abutting pours, which creates a higher quality connection than simply butting the two pours with nothing to interconnect them.
118⟩ Why are LNG pipes curved?
LNG pipes are curved because LNG is condensed gas (-164 deg cel) so it can expand the pipes that is what engineers designed the LNG pipes are curve type.
119⟩ What does a rolling offset look like?
Rolling offsets are used in the piping and sheet metal (ductwork) trades, a rolling offset changes the elevation and locaton of the piping or duct usually by using two fittings to offset around obstacles. Rolling offsets are used mostly when you are limited to the size of the fittings in order to change your elevation and location.
Rolling offsets are used in the piping and sheet metal (ductwork) trades, a rolling offset changes the elevation and locaton of the piping or duct usually by using two fittings to offset around obstacles. Rolling offsets are used mostly when you are limited to the size of the fittings in order to change your elevation and location
120⟩ What do you mean by the term thread size Please explain what does 0.125 Inch stand for in 0.125 Inch NPT thread?
One thread per .125 inch or 8 threads per inch
One thread per .125 inch or 8 threads per inch
