HSBTE Applied Physics-I 1st Semester Examination July 23: Question Paper with Answers for Diploma in Engineering Students

HSBTE Applied Physics-I, 1st Semester Examination: July 23, Questions with Answers to all HSBTE Questions.

220013/210013 HSBTE July 23. Time : 3 Hrs. M.M.: 60

1st Sem. Branch: Sub: Applied Physics/Applied Physics-I

SECTION-A

Note: Multiple choice questions. All questions are compulsory (6x1=6)

Q.1 M1L1T-2 is dimensional formula of

a) Velocity b) Force c) Length d) Acceleration. Ans: b) Force

Q.2 The splitting of a single force into rectangular components is called

a) Resolution of force b) Parallelogram law

c) Triangle law d) Newton law. Ans: a) Resolution of force

Q.3 The energy due to the motion of the body is called

a) Potential energy   b) Transformation of energy

c) Kinetic energy d) None of the above. Ans: c) Kinetic energy.

Q.4 Stress is directly proportional to strain and is called

a) Newton’s law b) Surface Tension

c) Viscosity d) Hooks law. Ans: d) Hooks law

Q.5 The rate of doing work is called

a) Power b) Kinetic Energy

c) Potential energy d) None of the above. Ans: a) Power

Q.6 Action and reaction are equal and opposite is called

a) Hooks law b) Newton’s First law

c) Newton’s second law d) Newton’s third law. Ans: d) Newton’s third law.

SECTION-B

Note: Objective/ Completion type questions. All questions are compulsory. (6x1=6)

Q.7 The full form of CGS is __________. Ans: Centimeter-Gram-Second.

Q.8 Define Time Period.

Ans: Time period is the duration or the amount of time taken for one complete cycle of a repetitive motion or a periodic event. It is commonly used in the context of oscillatory or cyclical phenomena, such as the motion of a pendulum, the rotation of the Earth around its axis, or the vibration of a tuning fork.

In mathematical terms, the time period (T) is the reciprocal of the frequency (f). It is represented by the equation:

T = 1/f

T is the time period,

f is the frequency.

The unit of time period is seconds (s). It represents the time taken for one complete cycle to occur.

Q.9 Define Positive Work.

Ans: Positive work is done when the force applied to an object results in displacement in the direction of the force. Or, positive work occurs when the force and the displacement have the same direction. The formula for calculating work (W) is given by:

W=F⋅d

W is the work done,

F is the force applied,

d is the displacement.

If the angle (θ) between the force and displacement vectors is 0 degrees (cosine of 0 is 1), then the work done is positive. Mathematically, this can be expressed as:

W=F⋅d⋅cos(θ)

For example, lifting a book straight up requires positive work because the force applied is in the upward direction, and the book is displaced in the same upward direction

.10 Define Surface Tension.

Ans: “Surface tension is the force acting on the surface of a liquid that tends to minimize the area of the surface”.

Mathematically, surface tension (T) is defined as the force (F) acting per unit length (L) along the interface between two liquids or a liquid and a gas:

T = F/L

The unit of surface tension in the International System of Units (SI) is Newton per meter (N/m).

Note: The molecules at the surface of a liquid experience a net inward force due to the cohesive forces with the molecules below the surface. This force creates a "skin" on the surface. This makes liquid behave like an elastic sheet. The molecules at the surface are drawn toward the interior of the liquid. This results in a minimized surface area.

Q.11 Define Rotational Motion.

Ans: Rotational motion is the movement of an object around an axis or a point that causes the object to spin or rotate. This type of motion involves a change in the orientation of an object to its axis of rotation.

Rotational motion is common in various natural and man-made systems. Examples of rotational motion include the Earth's rotation on its axis, the spinning of a wheel, the turning of gears, and the motion of a propeller.

Q.12 Define the Principle of Homogeneity.

Ans: The Principle of Homogeneity states that in any equation representing a physical law or relationship the dimensions (units) on both sides of the equation must be consistent. Or each term in the equation must have the same dimensions. This ensures the equation is dimensionally correct.

This principle is particularly useful in dimensional analysis. Dimensional analysis is a technique that involves studying the dimensions of physical quantities. This study derives relationships and identifies dimensionless parameters.

SECTION-C

Note: Short answer type questions. Attempt any eight questions out of ten questions. (8x4=32)

Q.13 Define Fundamental and Derived Quantities. Give two examples of each.

Ans: Fundamental quantities are the basic, independent quantities that are used to define other physical quantities. These fundamental quantities form the basis of a system of measurement.

Derived quantities are derived from one or more fundamental quantities through mathematical relationships. These relationships involve multiplication, division, or exponentiation of the fundamental quantities.

Examples of Fundamental Quantities:

• 1. Length (L): Length is a fundamental quantity and is typically measured in meters (m). It is used to define other quantities like area and volume.

• 2. Time (T): Time is a fundamental quantity, measured in seconds (s). It is used in motion and various dynamic phenomena.

Examples of Derived Quantities:

• 1. Area (A): Area is derived from the fundamental quantity length (L) by squaring it. The unit of area is square meters (m²).

• 2. Velocity (v): Velocity is derived from fundamental quantities length (L) and time (T). It is expressed as meters per second (m/s).

Note: The choice of fundamental quantities may vary. It depends on the system of units being used. In the International System of Units (SI), there are seven base or fundamental quantities, which include length, time, mass, electric current, temperature, amount of substance, and luminous intensity. All other physical quantities are derived from these base quantities.

Q.14 Check the correctness of

a. V = u + a t                    b). F = m a

Ans:

a. V = u+at

• V is the final velocity,

• u is the initial velocity,

• a is the acceleration,

• t is the time.

Checking the dimensions on both sides of the equation:

On the left-hand side

• The dimensions of velocity ([V]) are [L] [T]−1.

• The dimensions of initial velocity ([u]) are [L] [T]−1.

• The dimensions of acceleration ([a]) are [2[L] [T]−2.

• The dimensions of time ([t]) are [T].

On the right-hand side:

[u]+[a][t]=[L][T]−1+[L][T]−2[T]=[L][T]−1+[L][T]−1= [L][T]−1

This matches the dimensions of velocity ([V]).

Therefore, the equation is dimensionally correct.

b. F =ma

F is the force,

m is the mass,

a is the acceleration.

Checking the dimensions on both sides of the equation:

On the left-hand side:

• The dimensions of force ( [F]) are [M][L][T]−2.

• The dimensions of mass ( [m]) are [M].

• The dimensions of acceleration ( [a]) are [ [L][T]−2.

On the right-hand side:

[m][a] = [M][L][T]−2

This matches the dimensions of force ([F]). Therefore, the equation is dimensionally correct.

Q.15 Define scalar and vector quantities. Give two examples of each.

Ans:

Scalar Quantity: A scalar quantity is a physical quantity that has only magnitude (size) and no direction. Scalar quantities are completely described by their numerical value and the appropriate unit of measurement.

Examples of Scalar Quantities:

• 1. Mass (m): Mass is a scalar quantity that represents the amount of matter in an object. Its units are measured in kilograms (kg).

• 2. Temperature (T): Temperature is a scalar quantity that indicates the hotness or coldness of an object. Its units are measured in degrees Celsius (°C) or Kelvin (K).

Vector Quantity: A vector quantity is a physical quantity that has both magnitude and direction. Vectors are represented by arrows, where the length of the arrow corresponds to the magnitude. The direction of the arrow indicates the direction of the vector.

Examples of Vector Quantities:

• 1. Displacement (d): Displacement is a vector quantity that represents the change in position of an object. It has both magnitude (distance) and direction. It is expressed in units such as meters (m).

• 2. Velocity (v): Velocity is a vector quantity that represents the rate of change of an object's position to time. It has both magnitude (speed) and direction. It is often expressed in units such as meters per second (m/s).

Q.16 Define Centripetal and Centrifugal force. Give the formula of each. The same question in the HSBTE February 23 Examination.

Ans:

Centripetal Force: “Centripetal force is the force that acts on an object moving in a circular path, directed toward the center of the circle or the axis of rotation”. Its primary purpose is to keep the object in circular motion by constantly changing its direction. The formula for centripetal force (Fc​) is given by: Fc​=rm⋅v2​

• Fc​ is the centripetal force,

• m is the mass of the object,

• v is the speed of the object,

• r is the radius of the circular path.

Centrifugal Force: Centrifugal force is referred to as a "fictitious" or "pseudo" force. Centrifugal force in the circular motion acts outward from the center of rotation”. It acts opposite to the centripetal force. It is treated as the negative of the centripetal force:

Fcentrifugal ​ = −Fcentripetal

Note: It's important to note that centrifugal force does not result from any physical interaction. It is a result of viewing the motion from a non-inertial (accelerated) frame. In an inertial frame, no outward force is acting on the object.

Centripetal force is a real force acting toward the center of rotation, keeping an object in circular motion. Centrifugal force is a pseudo force that appears to act outward in a rotating reference frame. The two forces are related by Newton's third law, but centrifugal force is not a true force in the classical sense.

Q17 Define Potential energy. Derive an expression for it.

Ans: Potential energy is a form of energy associated with the position of an object within a force field. The potential energy is used to describe the energy stored in an object due to its position or state.

The expression for gravitational potential energy (U) near the surface of the Earth is derived using the gravitational force and the work-energy principle. The gravitational potential energy is associated with the position of an object in a gravitational field.

Derivation of Gravitational Potential Energy:

Consider an object of mass m placed at a height ℎ above the Earth's surface.

1. Force of Gravity: The force of gravity (F) acting on the object is given by Newton's law of gravitation: F=m⋅g

g is the acceleration due to gravity (approximately 9.8m/s square near the Earth's surface).

Work Done: The work done (W) in raising the object to a height h against gravity is the force multiplied by the displacement: ℎW=F⋅h

Substituting the expression for F: ℎW=m⋅g⋅h

2. Gravitational Potential Energy: The work done against gravity is stored as gravitational potential energy (U): ℎU=m⋅g⋅h

So, the expression for gravitational potential energy near the Earth's surface is: ℎU=m⋅g⋅h

• U is the gravitational potential energy,

• m is the mass of the object,

• g is the acceleration due to gravity,

• h is the height of the object above a reference point.

This formula represents the amount of energy an object possesses due to its position in a gravitational field. The potential energy is directly proportional to both the mass of the object and its height above the reference point

Q.18 Write a short note on the Transformation of Energy. The same question in the HSBTE February 23 Examination.

Ans: The transformation of energy refers to the process by which energy changes from one form to another while maintaining its total amount within a closed system. This concept is of the law of conservation of energy. The law of conservation of energy states that energy cannot be created or destroyed only transformed from one form to another.

Energy exists in various forms, including kinetic energy (energy of motion), potential energy (stored energy), thermal energy (heat), chemical energy, electrical energy, and more. The transformation of energy occurs in a wide range of natural and human-made processes.

Some common examples of the transformation of energy:

• 1. Mechanical to Electrical: In a generator, mechanical energy (from the rotation of a turbine) is transformed into electrical energy.

• 2. Chemical to Thermal: Combustion processes, such as burning fossil fuels or wood transform chemical energy stored in the fuel into thermal energy (heat), and mechanical energy.

• 3. Potential to Kinetic: The object accelerates downward when an object falls under the influence of gravity. Here potential energy is converted into kinetic energy.

• 4. Electrical to Light: In a light bulb, electrical energy is transformed into light energy and thermal energy. The filament in the bulb heats up due to the flow of electricity. This produces both light and heat.

• 5. Solar to Electrical: Photovoltaic cells are commonly used in solar panels. It transforms sunlight (solar energy) into electrical energy through the photovoltaic effect.

• 6. Nuclear to Thermal: In nuclear power plants, the energy released from nuclear reactions is transformed into thermal energy. This thermal energy is then used to produce steam and generate electricity through turbines.

Q.19 Write a short note on absolute pressure and gauge pressure.  The same question in the HSBTE February 23 Examination.

Ans:

Absolute pressure is the total pressure exerted by a fluid, including both atmospheric pressure and the pressure exerted by the fluid itself. It is measured relative to a vacuum. Absolute pressure is the pressure of the fluid in addition to the atmospheric pressure that acts on the fluid.

The formula for absolute pressure (Pabsolute​)

Pabsolute​=Patmospheric​+Pgauge​

• · Pabsolute​ is the absolute pressure.

• · Patmospheric​ is the atmospheric pressure. Atmospheric pressure is the pressure exerted by the Earth's atmosphere at a given location.

• · Pgauge​ is the gauge pressure. Gauge pressure is the pressure measured above atmospheric pressure (if positive) or below atmospheric pressure (if negative).

When measuring pressure, devices like pressure gauges display gauge pressure. To obtain absolute pressure, atmospheric pressure must be added.

Absolute pressure is important in various engineering and scientific applications such as in fluid dynamics, and thermodynamics. The measurements involve pressure-sensitive instruments. It provides a complete measure of the total pressure experienced by a fluid. It is crucial for accurate calculations and analysis in many fields.

Gauge pressure is the pressure measured above atmospheric pressure. It represents the pressure of a fluid or gas relative to the atmospheric pressure at a specific location. In most pressure-measuring devices, such as pressure gauges, the reading displayed is gauge pressure.

The formula for gauge pressure (Pgauge​) is: Pgauge​=Pabsolute​−Patmospheric​

• Pgauge​ is the gauge pressure,

• Pabsolute​ is the absolute pressure (including atmospheric pressure),

• Patmospheric​ is the atmospheric pressure.

If the gauge pressure is positive, it means the pressure is above atmospheric pressure. If it's negative, it indicates a pressure lower than atmospheric pressure.

For example, if a pressure gauge reads 300 kPa, and the atmospheric pressure is 100 kPa, the gauge pressure would be 200 kPa (300 kPa - 100 kPa). This value represents the pressure exerted by the fluid or gas above and beyond the atmospheric pressure.

Gauge pressure is important in applications where absolute pressure is not the primary concern. It is commonly used in fields such as fluid mechanics, engineering, and industrial processes.

Q.20 Convert force of 200 Newton into Dyne. Similar question in the HSBTE February 23 Examination.

Ans: The dyne is a unit of force in the CGS (centimeter-gram-second) system. It is defined as the force required to accelerate a mass of one gram at a rate of one centimeter per second squared. The relationship between newtons (N) and dynes (dyn) is as follows: 1N =100000 dyne.

Force in dynes=Force in Newtons×(100000dyn/N)

Force in dynes=200 N×100000 dyn/NN

Force in dynes=2×10000000dyn

Therefore, a force of 200 Newtons is equivalent to 2×10000000 dynes.

Q.21 Explain heat and temperature on the basis of Kinetic Theory. Similar question in the HSBTE February 23 Examination.

Ans: The Kinetic Theory of Matter provides a microscopic explanation for the concepts of heat and temperature. It is based on the motion of particles at the molecular or atomic level. According to this theory:

Heat: · Heat is a form of energy associated with the random motion (kinetic energy) of particles (atoms or molecules) within a substance. · When a substance absorbs heat, the kinetic energy of its particles increases. It leads to faster and more chaotic motion. Conversely, when heat is released, the kinetic energy decreases.

Temperature: · Temperature is a measure of the average kinetic energy of the particles in a substance. It reflects how fast, on average, the particles are moving. · The higher the temperature, the greater the average kinetic energy of the particles. A lower temperature corresponds to a lower average kinetic energy. · Temperature is a scalar quantity and does not depend on the type or mass of particles. It is a measure of the intensity of heat.

Q.22 Write any four properties of heat radiation.

Ans: Heat radiation is a mode of heat transfer that occurs through electromagnetic waves in the infrared region of the electromagnetic spectrum. It does not require a medium for propagation and can travel through a vacuum. The following are four properties of heat radiation:

1. Electromagnetic Waves: Heat radiation consists of electromagnetic waves in the infrared (IR) region of the spectrum. These waves have various wavelengths. Their energy is proportional to their frequency.

2. Travel Through a Vacuum: Heat radiation does not require a material medium for transmission. This property allows heat to be radiated and received across space or in a vacuum. This characteristic transfer of heat from the Sun to the Earth through space.

3. Speed of Light: Heat radiation travels at the speed of light (c) in a vacuum. This is approximately3×100000000m/s. The speed of heat radiation depends on the medium through which it travels. But in a vacuum, it reaches its maximum speed.

4. Dependence on Temperature and Emissivity: The rate of heat radiation is influenced by the temperature of the radiating object. According to Stefan-Boltzmann's law, the total energy radiated per unit surface area is proportional to the fourth power of the absolute temperature (T4). Emissivity is another important factor. Emissivity (e) is a measure of how efficiently an object emits radiation compared to a perfect emitter (a blackbody). A perfect emitter has an emissivity of 1, while real objects have emissivities between 0 and 1.

SECTION-D

Note: Long answer type questions. Attempt any two questions out of three questions. (2x8=16)

Q.23 a. Explain the system of units. A similar question in the HSBTE February 23 Examination.

Systems of units are standardized sets of units for expressing measurements. These systems provide a reliable and logical. These measurements are universally understood. There are two types of systems of units. These are the International System of Units (SI) and the Imperial.

1. International System of Units (SI): Base Units:

• · Meter (m) for length

• · Kilogram (kg) for mass · Second (s) for time

• · Ampere (A) for electric current · Kelvin (K) for temperature

• · Mole (mol) for the amount of substance

• · Candela (cd) for luminous intensity

Derived Units: These are combinations of base units to express other quantities. For example, the unit for speed is meters per second (m/s), which is a derived unit. Prefixes: SI uses prefixes to denote decimal multiples or submultiples of units. For example, a kilometer (km) is a thousand meters, and a millisecond (ms) is one-thousandth of a second.

2. Imperial and U.S. Customary Systems: Length:

•  Inch (in), foot (ft), yard (yd),

• mile (mi)

• Mass: Ounce (oz), pound (lb), ton (short ton or long ton)

• Time: Second (s), minute (min), hour (h).

• Volume: Fluid ounce (fl oz), cup, pint, quart, gallon.

• Temperature: Fahrenheit (°F) in the U.S. Customary System, but Celsius (°C) is also used in some contexts.

• Force: Pound-force (lbf),

• Energy: British thermal unit (BTU),

• Pressure: Pound-force per square inch (psi) The SI system is widely used in scientific and most international contexts. The Imperial and U.S. Customary Systems are more common in the United States and some other countries. The adoption of the SI system is increasing globally in scientific and engineering fields. It's important to note that using consistent systems of units is crucial to avoid errors and misunderstandings in measurements and calculations. Scientists, engineers, and professionals across different disciplines adhere to specific unit systems to ensure accurate and standardized communication.

b. Define Newton’s first and second law with two examples each. Similar question in HSBTE February 23 Examination.

Ans:

Newton's First Law (Law of Inertia): Newton's first law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by a net external force. Or an object will maintain its state of motion (whether at rest or moving at a constant velocity) unless an external force is applied to it.

Examples of Newton's First Law:

• 1. Stationary Car: Consider a car at rest. According to Newton's first law, the car will remain at rest until an external force (such as braking or an impact) is applied.

• 2. Moving Ball on a Frictionless Surface: If a ball is rolling on a frictionless surface, it will continue to roll indefinitely in a straight line at a constant speed. Its rolling is reduced by a friction force acting on it. This demonstrates the idea that an object in motion will remain in motion with constant velocity if no external force is applied.

Newton's Second Law: Newton's second law states that the acceleration of an object is directly proportional to the net force acting upon it and inversely proportional to its mass. This law is expressed by the equation F=ma. “F” is the net force, “m” is the mass of the object, and “a” is the acceleration produced.

Examples of Newton's Second Law:

• 1. Acceleration of a Car: When a constant force is applied to a car, the car accelerates. The greater the force applied, the greater the acceleration. Additionally, a heavier car (larger mass) will experience less acceleration for the same force compared to a lighter car.

• 2. Gravity and Free-Falling Object: A free-falling object near the surface of the Earth experiences the force of gravity. The acceleration of the object is directly proportional to the force of gravity and inversely proportional to its mass. This relationship is described by Newton's second law.

Q.24 Explain Conduction, Convection, and Radiation with examples. A similar question in the the HSBTE February 23 Examination.

• Ans: Conduction, convection, and radiation are three primary mechanisms of heat transfer. Each occurs in different ways

• 1. Conduction: Definition: Conduction is the process of heat transfer through direct contact between particles of a substance. It occurs in solids, where the particles are closely packed together.

  • Example: Heating one end of a metal rod, the particles at that end gain energy and vibrate. These vibrations are then passed on to adjacent particles, and this continues throughout the rod. This leads to the transfer of heat from one end to the other

• 2. Convection: Definition: Convection is the process of heat transfer through the movement of fluids (liquids or gases). It involves the transfer of heat by the actual movement of the heated fluid from one place to another.

  • Example: Boiling water is a classic example of convection. As water is heated, the molecules near the heat source become energized and move upward. Cooler, denser water then moves downward to replace it. This creates a circular flow of water, transferring heat throughout the entire container

• 3. Radiation: Definition: Radiation is the transfer of heat through electromagnetic waves. Unlike conduction and convection, radiation does not require a medium and can occur in a vacuum.

  • Example: The sun's energy reaching the Earth is a form of radiation. The sun emits electromagnetic waves (including visible light) that travel through the vacuum of space and reach the Earth. Another example is the heat you feel when sitting close to a fire or a hot object without direct contact.

Conclusion: Conduction involves the transfer of heat through direct contact with solids. Convection involves the transfer of heat through the movement of fluids. Radiation involves the transfer of heat through electromagnetic waves and can occur in a vacuum.

Q.25 Define the banking of roads. Derive an expression for it.

Ans: Banking of roads is the inclining

of the road surface at a certain angle to the horizontal. The purpose of road banking is to reduce the tendency of a vehicle to overturn or skid at curved sections of the road. By inclining the road surface, a component of the normal reaction force provides the necessary centripetal force for the vehicle's circular motion.

Dr Pramila Singh