Mechanical Science-DEP(S)2022

1.Define the term "viscosity" and explain its importance in fluid mechanics

• Viscosity is the measure of a fluid's ability to conduct electricity.
• Viscosity is the measure of a fluid's color.
• Viscosity is the measure of a fluid's ability to produce sound.
• Viscosity is the measure of a fluid's resistance to deformation or flow.

2.A fluid with a density of 800 kg/m³ flows through a pipe with a velocity of 4 m/s. Calculate the dynamic viscosity if the dynamic pressure is 1000 N/m².

• 0.5 Pa.s
• 0.3125 Pa.s
• 0.75 Pa.s
• 1.25 Pa.s

3.Explain the purpose and functioning of a governor in a steam engine. How does it control the engine's speed?

• It controls the engine's speed by adjusting the color of the steam.
• It controls the engine's speed by playing music to the engine.
• It controls the engine's speed by changing the size of the engine.
• It controls the engine's speed by regulating the flow of steam to the engine.

4.Differentiate between a centrifugal governor and a Hartnell governor. Provide examples of where each type is typically used.

• A centrifugal governor is used in power plants, while a Hartnell governor is used in coffee makers.
• A centrifugal governor is used in cars, while a Hartnell governor is used in smartphones.
• A centrifugal governor is used in airplanes, while a Hartnell governor is used in washing machines.
• The correct answer for the question is to provide a detailed explanation of the differences between a centrifugal governor and a Hartnell governor, along with examples of where each type is typically used.

5.Describe the advantages and disadvantages of a belt drive system in power transmission. Give practical examples of applications where belt drives are commonly used.

• The advantages of a belt drive system include high power transmission, noisy operation, and inflexibility.
• Practical examples of applications where belt drives are commonly used include smartphones, bicycles, and laptops.
• The disadvantages of a belt drive system include low maintenance, smooth operation, and high efficiency.
• The advantages of a belt drive system include flexibility, quiet operation, and shock absorption, while the disadvantages include slippage and limited power transmission. Practical examples of applications where belt drives are commonly used include conveyor systems, agricultural machinery, and industrial fans.

6.Discuss the importance of gear trains in power transmission. Explain the concept of gear ratios and how they affect speed and torque.

• Gear trains are important for power transmission and gear ratios determine the relationship between speed and torque.
• Gear trains are only used in bicycles and have no other applications
• Gear ratios have no impact on speed and torque
• Gear trains are only important for aesthetic purposes

7.State the first law of thermodynamics and provide a practical example illustrating its application.

• The first law of thermodynamics states that energy can be created or destroyed, only transformed from one form to another. An example of its application is the conversion of heat energy into light energy in a light bulb.
• The first law of thermodynamics states that energy can be created or destroyed, only transformed from one form to another. An example of its application is the conversion of sound energy into electrical energy in a speaker.
• The first law of thermodynamics states that energy can be created or destroyed, only transformed from one form to another. An example of its application is the conversion of chemical energy into nuclear energy in a power plant.
• The first law of thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. An example of its application is the conversion of electrical energy into mechanical energy in a car engine.

8.What is an ideal gas? How does the ideal gas law (PV = nRT) relate to real gases? Explain any limitations of the ideal gas law.

• The ideal gas is a hypothetical gas whose molecules occupy negligible space and have no interactions. The ideal gas law relates the pressure (P), volume (V), amount of substance (n), and temperature (T) of an ideal gas. However, real gases have volume and interactions between molecules, so they do not always follow the ideal gas law. The limitations of the ideal gas law include the assumption of negligible volume of gas molecules and no intermolecular forces.
• The ideal gas law does not include the temperature of the gas
• An ideal gas is a gas that has a perfect smell and taste
• The ideal gas law only applies to gases found in outer space

9.Define stress and strain in the context of materials science. How are they related, and what are the different types of stress and strain?

• Stress is the amount of pressure a material can handle, while strain is the color change in a material.
• Stress is the force applied to a material per unit area, while strain is the deformation of a material in response to stress. They are related through Hooke's Law, and the different types of stress include tensile stress, compressive stress, and shear stress, while the different types of strain include tensile strain, compressive strain, and shear strain.
• Stress is the speed at which a material breaks, while strain is the smell of the material.
• Stress is the weight of a material, while strain is the temperature at which it melts.

10.A steel rod with a diameter of 10 mm and a length of 1 meter is subjected to a tensile load of 20,000 N. Calculate the stress and strain experienced by the rod. Given: Young's Modulus of Steel = 200 GPa.

• Stress = 500 N/m^2, Strain = 0.1
• Stress = 200000 N/m^2, Strain = 0.001
• Stress = 159154.943 N/m^2, Strain = 0.01
• Stress = 10000 N/m^2, Strain = 0.05