Basics Of Mechanical Engineering

A black body is a theoretical object that absorbs all radiation incident upon it, regardless of wavelength or angle of incidence. It does not reflect or transmit any radiation. This property allows it to be used as a standard for comparison in various fields, such as thermodynamics and spectroscopy. The term "black" refers to the fact that the object appears black when it is at thermal equilibrium with its surroundings, as it emits radiation at all wavelengths.

A drilling machine is a versatile tool that is capable of performing various operations such as drilling, reaming, and boring. Drilling involves creating holes in a material, reaming is the process of enlarging or finishing a hole, and boring is used to enlarge an existing hole or create a larger hole. Therefore, all of the mentioned operations can be performed by a drilling machine.

Viscosity is the property of a fluid that describes its internal resistance. It refers to the measure of a fluid's resistance to flow or its thickness. A fluid with high viscosity flows slowly, while a fluid with low viscosity flows quickly. This property is important in various applications, such as in the design of lubricants, paints, and in understanding the behavior of fluids in pipes and channels. Therefore, viscosity is the correct answer to the question.

Stress is defined as the internal resistive force within a material that arises when it is subjected to external forces or loads. It is a measure of the material's ability to withstand deformation or failure under these forces. Stress can be caused by various factors such as pressure, tension, or shear forces acting on the material. Therefore, the correct answer is "Internal resistive force" as stress is an internal force that opposes external forces.

The correct answer is H = I2RT. This equation represents the heat generated in resistance welding. The variables in the equation are as follows: H represents the heat generated, I represents the current flowing through the circuit, R represents the resistance of the material being welded, and T represents the time duration of the welding process. The equation shows that the heat generated is directly proportional to the square of the current, the resistance, and the time duration.

Area strain is not a basic type of strain because it is not commonly used or recognized in the field of mechanics or materials science. The basic types of strain include compressive strain, shear strain, and volume strain, which are widely studied and understood. Area strain, on the other hand, refers to the change in the size or shape of a two-dimensional surface, which is not as commonly analyzed or measured in strain analysis.

Grinding is commonly used on cast iron because it is a hard and brittle material that can be difficult to shape or cut using other methods. Grinding involves using an abrasive wheel to remove material from the surface of the cast iron, allowing for precise shaping and smoothing. The hardness of cast iron makes it suitable for grinding, as it can withstand the pressure and friction generated during the process without deforming or wearing down excessively. Additionally, grinding helps to achieve a smooth and polished finish on cast iron surfaces.

The correct answer is W/m.K. Thermal conductivity is a measure of a material's ability to conduct heat. It is defined as the amount of heat that can be conducted through a unit area of a material of unit thickness in a unit time when there is a unit temperature difference between the two sides. The unit W/m.K represents the amount of heat energy (in watts) that can be conducted through a meter of the material with a temperature difference of 1 Kelvin.

A rack and pinion gear system is used to convert rotary motion into translating motion. In this system, a straight toothed rack is engaged with a pinion gear. As the pinion gear rotates, it moves the rack linearly, allowing for the conversion of rotary motion into a straight-line motion. This gear system is commonly used in various applications, such as steering systems in vehicles, where the rotational motion of the steering wheel is converted into the linear motion of the wheels.

The train crosses a stationary pole in 9 seconds, which means it covers the length of the train in that time. We need to find the length of the train, so the correct answer is 154 meters.

The correct sequence for the rearranged sentences is 4 2 1 3. The paragraph starts by stating that South Africa has been a racially divided society since the arrival of European settlers in 1652. Then, it mentions that various situational and political changes have occurred over the past three and a half centuries. Next, it explains how different rulers and governments dealt with different groups in a compartmentalized manner, leading to a deeply embedded fragmented society. Finally, it states that this division became even more prominent from 1948 until the new Constitution was established in 1994.

The size of the lathe is determined by multiple factors, including the maximum job length that can be held between centers in millimeters and the height of centers measured over the lathe bed. Therefore, the correct answer is "all of the above" as all of these specifications contribute to specifying the size of the lathe.

The probability of getting a sum of 9 from two throws of a dice can be calculated by finding the number of favorable outcomes and dividing it by the total number of possible outcomes. In this case, there is only one favorable outcome, which is getting a 3 on the first throw and a 6 on the second throw. The total number of possible outcomes is 6*6=36, as there are 6 possible outcomes for each throw. Therefore, the probability is 1/36, which simplifies to 1/9.

Anemometer is a device used to measure the velocity of wind or air. It works by capturing the force of the wind and converting it into a measurement of speed. By measuring the velocity, anemometers help in determining the speed and direction of the wind, which is crucial in various fields such as meteorology, aviation, and environmental monitoring. Therefore, anemometer is specifically used to measure velocity rather than pressure, viscosity, or density.

The measurement of temperature is based on the zeroth law of thermodynamics, which states that if two systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law allows for the establishment of a temperature scale and the comparison of temperatures between different systems. By using the principles of the zeroth law, thermometers can be calibrated and measurements of temperature can be made.

When a bar is fixed vertically at its upper end, its elongation is determined by the weight applied to it and the material's properties. The equation Wl/2AE represents the elongation of the bar, where W is the weight, l is the length, A is the cross-sectional area, and E is the modulus of elasticity of the material. This equation is derived from Hooke's Law, which states that the elongation of an object is directly proportional to the applied force and inversely proportional to the cross-sectional area and modulus of elasticity. Therefore, the correct answer is Wl/2AE.

The word pair "INDIGENT: WEALTHY" represents an opposite relationship, where "indigent" means poor and "wealthy" means rich. Similarly, the word pair "gauche:graceful" also represents an opposite relationship, where "gauche" means awkward or clumsy and "graceful" means elegant or poised. Therefore, the correct answer is "gauche:graceful".

A flywheel is used in a punch press to store and release energy. When the punch press is in operation, the flywheel spins and stores energy. This stored energy is then released to provide the necessary force for the punching action. The flywheel helps to maintain a consistent and smooth operation by storing and releasing energy in a controlled manner. This is particularly important in punch presses, where precise and powerful punches are required.

The steel containing 0.8% carbon has a structure of ferrite because ferrite is the phase that forms in low carbon steels. Ferrite is a solid solution of carbon in iron, and it has a body-centered cubic (BCC) crystal structure. It is relatively soft and ductile, making it suitable for applications where toughness is required. In steels with higher carbon content, other phases such as pearlite, cementite, or martensite may form, but with 0.8% carbon, the dominant phase is ferrite.

A can do 1/15th of the work in a day and B can do 1/20th of the work in a day. Together, they can do (1/15 + 1/20) = 7/60th of the work in a day. In 4 days, they would have completed (4 * 7/60) = 7/15th of the work. Therefore, the fraction of the work that is left is (1 - 7/15) = 8/15.

The correct answer is "Absolute pressure = Gauge pressure + Atmospheric pressure." This equation represents the relationship between absolute pressure, gauge pressure, and atmospheric pressure. Absolute pressure is the total pressure exerted by a fluid, including both the atmospheric pressure and any additional pressure measured by a gauge. Therefore, to calculate the absolute pressure, one must add the gauge pressure to the atmospheric pressure.

Mintu wanted to take a day off from school, so he pretended to be sick and remained in bed. Thinking that he was really sick, his father summoned the family doctor. Therefore, sentence 2 should come third in the paragraph.

A ductile structure is one that can undergo significant plastic deformation before fracturing. This means that the material can be stretched or bent without breaking. The given answer, "is much larger than the elastic deformation," is correct because it indicates that the plastic deformation is greater than the elastic deformation. This implies that the material can withstand a large amount of deformation before it ultimately fractures, making it ductile.

Drawing is the correct answer because it refers to the process of making cup-shaped parts from sheet metal by pulling the blank into dies with the help of a punch. This process involves stretching the metal to conform to the shape of the die, resulting in a cup-like form. Spinning involves rotating a flat sheet of metal while pressing it against a form to create a cylindrical shape. Extrusion involves forcing the metal through a die to create a continuous profile. Forming is a general term that encompasses various metal shaping processes.

The cutting time for turning is calculated by dividing the length of the job (l) by the product of the feed rate (f) and the rpm of work (n). This is because the cutting time is inversely proportional to the product of the feed rate and the rpm of work. Therefore, the correct formula to calculate the cutting time is l / (f x n) minutes.

From the given group of 7 men and 6 women, we need to select 5 people for the committee with at least 3 men.

We can consider two cases:
1) Selecting 3 men and 2 women:
The number of ways to select 3 men from 7 is 7C3 = 35.
The number of ways to select 2 women from 6 is 6C2 = 15.
So, the total number of ways to select 3 men and 2 women is 35 * 15 = 525.

2) Selecting 4 men and 1 woman:
The number of ways to select 4 men from 7 is 7C4 = 35.
The number of ways to select 1 woman from 6 is 6C1 = 6.
So, the total number of ways to select 4 men and 1 woman is 35 * 6 = 210.

Adding the two cases, we get a total of 525 + 210 = 735 ways.

Therefore, the correct answer is 735.

A flywheel has multiple functions. It stores and releases energy as needed during the work cycle, helping to maintain a consistent power output. It also reduces the amplitude of speed fluctuations, ensuring a smoother operation. Additionally, a flywheel can help in reducing the power capacity of the motor by providing an extra source of energy during peak demand periods. Therefore, all of the given options correctly describe the functions of a flywheel.

The circular pitch of a gear with diameter d and a number of teeth t is given by Πd/t. This formula calculates the distance between corresponding points on adjacent teeth along the circumference of the gear.

The second law of thermodynamics states that heat transfer occurs from an object at a higher temperature to an object at a lower temperature. This law explains the direction of heat flow and the concept of entropy, which is the measure of the disorder or randomness in a system. It also states that it is impossible to convert all heat into work without any loss. Therefore, the second law of thermodynamics is the correct answer as it specifically deals with heat transfer.

In a cantilever, the bending moment is maximum at the fixed end. This is because the fixed end of the cantilever is the point where the cantilever is anchored or supported, and therefore experiences the highest amount of force or load. As a result, the fixed end undergoes the most significant bending moment compared to the other parts of the cantilever.

Spiral gears are used to connect non-parallel and non-intersecting shafts. Unlike straight bevel gears, which have straight teeth, spiral gears have angled teeth that gradually engage, resulting in a smoother and quieter operation. This makes spiral gears ideal for applications where precise and efficient power transmission is required, such as in automotive transmissions and industrial machinery. Double helical gears, on the other hand, are used to connect parallel shafts and are not suitable for connecting non-parallel and non-intersecting shafts.

Counter sinking is the correct answer for making a chamfer on the edge of a hole. Counter sinking involves enlarging the top portion of the hole to create a flat or angled surface, which helps in reducing sharp edges and providing a chamfered effect. This operation is commonly used in metalworking and woodworking to improve the appearance and functionality of holes, especially when fasteners need to be flush-mounted or when the edges of the hole need to be chamfered for safety reasons.

Stainless steel is very difficult to grind due to its toughness and ability to work harden. The toughness of stainless steel makes it resistant to deformation and breakage, making it challenging to grind. Additionally, stainless steel has the ability to work harden, meaning that it becomes harder and more resistant to grinding as it is subjected to mechanical stress. Therefore, both the toughness and work hardening properties of stainless steel contribute to its difficulty in grinding.

Heat is mainly transferred by conduction, convection, and radiation in boiler furnaces. In a boiler furnace, conduction occurs when heat is transferred through direct contact between the hot surfaces of the furnace and the surrounding materials. Convection takes place as the hot air or gases rise and circulate within the furnace, transferring heat to the surrounding areas. Radiation occurs as heat is emitted in the form of electromagnetic waves from the hot surfaces of the furnace, which can then be absorbed by nearby objects and surfaces.

An isothermal process is a process in which the working substance neither receives nor gives heat to its surroundings during expansion or compression. This means that the temperature of the substance remains constant throughout the process. In an isothermal process, the energy transfer occurs only in the form of work done on or by the substance, while the heat transfer is zero. This is in contrast to an adiabatic process, where there is no heat transfer but the temperature of the substance can change. A hyperbolic process is not a recognized term in thermodynamics, so it is not the correct answer.

A lower pair refers to a type of mechanical joint where the relative motion between the two elements is a sliding or a rolling motion. In this case, a shaft rotating in a bush fits the definition of a lower pair as it involves a rotational motion of the shaft inside the bush, which can be considered as a sliding or rolling motion. On the other hand, a cam and follower mechanism involves a sliding or rolling motion as well, but it is classified as a higher pair due to the nature of the contact between the cam and the follower. Toothed gearing is also classified as a higher pair as it involves a rolling motion between the teeth of the gears. Therefore, the correct answer is shaft rotating in bush.

The Kelvin temperature scale is based on the triple point of water. The triple point of water is the temperature and pressure at which all three phases of water (solid, liquid, and gas) can coexist in equilibrium. It is a well-defined and reproducible point, making it an ideal reference for temperature measurement. The Kelvin scale defines the temperature unit "kelvin" based on the triple point of water, with 0 K being absolute zero, the lowest possible temperature. Therefore, the triple point of water is fundamental to the establishment of the Kelvin temperature scale.

The word "retaliatory" means to respond to an action with a similar action, usually in a negative or aggressive manner. The word "perfunctory" means to do something in a routine or superficial manner, without much effort or interest. The word "conciliatory" means to make peace or to try to resolve a conflict by being cooperative and compromising. The word "circuitous" means to take a longer route or to go around in a roundabout way. Therefore, "conciliatory" is the word that is closest in meaning to the opposite of "retaliatory".

The sentence is in the past tense, so the correct form of the verb "clear" should be "cleared." Therefore, the error is in part C, "Cleared by clouds."

Brazing is the process of joining two pieces of metal by introducing a non-ferrous alloy in a liquid state between them, which then solidifies. Unlike welding, which involves melting the base metals, brazing uses a lower temperature to melt the filler metal. This allows for the joining of dissimilar metals or metals with different melting points. The solidified filler metal forms a strong bond between the two pieces, creating a durable and reliable joint.

In a Newtonian fluid, shear stress is proportional to the rate of shear strain. This means that as the rate of shear strain increases (i.e., the fluid is being deformed more rapidly), the shear stress also increases proportionally. This relationship is a characteristic of Newtonian fluids, which have a constant viscosity and exhibit linear behavior under shear. The proportionality between shear stress and the rate of shear strain is described by the fluid's viscosity, which determines how easily the fluid flows and deforms under applied forces.

Cohesion refers to the attraction between molecules of the same substance. In the case of surface tension, cohesion is responsible for the molecules at the surface of a liquid to be more strongly attracted to each other compared to the molecules within the liquid. This creates a "skin" or "film" on the surface, causing the liquid to behave as if it has a stretched surface. Therefore, cohesion is the main factor contributing to surface tension.

The evaporator is the correct answer because it is the component in a refrigeration or air conditioning system that absorbs heat from the surrounding environment. It is responsible for evaporating the refrigerant, which in turn absorbs heat and cools the air or substance being refrigerated. The evaporator is typically located on the inside of the system and is where the cooling process begins.

The correct answer is "Diameter." In the context of gears, the diameter refers to the size of the gear, specifically the distance across the gear from one side to the other, passing through the center. The diameter is an important parameter in gear design as it determines the overall size and compatibility of the gear with other gears in a system. The pitch, module, and number of teeth are also important parameters, but they do not define the gear as being "of infinite" like the diameter does.

The correct answer is N1 / N2. This is because the velocity ratio of gears is determined by the ratio of the number of teeth on the gears, not the ratio of their speeds or diameters or torques. The formula for velocity ratio is N1 / N2, where N1 is the number of teeth on the first gear and N2 is the number of teeth on the second gear.

Newton's law of viscosity states that the rate of shear strain in a fluid is directly proportional to the shear stress applied to it. In other words, the viscosity of a fluid determines how it responds to an applied shear stress. Therefore, the correct answer is "viscosity and shear stress" because these two factors are the key components in Newton's law of viscosity.

The drag force exerted by a fluid on a body immersed in the fluid is due to viscous and gravity forces. Viscous forces arise because of the fluid's resistance to flow and the friction between the fluid and the body. Gravity forces come into play as the weight of the body causes it to move through the fluid, creating a drag force.

Let's assume the price of 1 chair is x and the price of 1 table is y. According to the given information, 10 chairs = 4 tables, so 10x = 4y. Also, 15 chairs + 2 tables = Rs. 4000, so 15x + 2y = 4000. Solving these two equations, we can find the values of x and y. Once we have the values of x and y, we can calculate the total price of 12 chairs and 3 tables by multiplying the respective prices and adding them up. The total price comes out to be Rs. 3500.

The relative density of a substance is defined as the ratio of its density to the density of a reference substance. In this case, the reference substance is usually water. Since the relative density of mercury is given as 1, it means that the density of mercury is equal to the density of water. Therefore, the correct answer is 1.

If the Reynolds number is less than 2000, the flow in a pipe is laminar. The Reynolds number is a dimensionless quantity that represents the ratio of inertial forces to viscous forces in a fluid flow. It is used to determine the type of flow, with values below 2000 indicating laminar flow and values above 4000 indicating turbulent flow. In this case, since the Reynolds number is less than 2000, the flow in the pipe is laminar.