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All questions of September Week 4 for NEET Exam

Material is said to be ductile if
  • a)
    a large amount of plastic deformation takes place between the elastic limit and the fracture point
  • b)
    fracture occurs soon after the elastic limit is passed
  • c)
    material cross section is not significantly reduced at failure
  • d)
    material breaks suddenly at little elongation
Correct answer is option 'A'. Can you explain this answer?

Nandini Iyer answered
A ductile material is one that can withstand a large amount of plastic deformation between the elastic limit and the fracture point.
A material that breaks suddenly when elongated or fracture occurs in it soon after the elastic limit is crossed is called a brittle material.
A ductile material that exhibits extra elongation or deformation and does not fracture is also referred as superplastic material.

 In which of the following reaction can equilibrium be attained
  • a)
    Reversible reaction
  • b)
    Cyclic reaction
  • c)
    Decomposition reaction
  • d)
    Irreversible reaction
Correct answer is option 'A'. Can you explain this answer?

Rajat Kapoor answered
Reversible Reaction
The common observation for any reactions when they are reacted in closed containers would not go to completion, for some given conditions like temperature and pressure.
For all those cases, only the reactants are found to be present in the intial stages, but with the progress of reaction, the reactants concentration decreases and to that of the products increases. A stage is finally reached where there is no more change of reactants and products concentration is observed. The state where the reactants and products concentrations do not show any visible change within a given period of time is better known as the state of chemical equilibrium. 
The reactant amount that remains unused depends upon the experimental conditions like concentration of components, temperature of the system, pressure of the system and the reaction nature.

You hang a flood lamp from the end of a vertical steel wire. The flood lamp stretches the wire 0.18 mm and the stress is proportional to the strain. How much would it have stretched if the wire had the same length but twice the diameter?
  • a)
    0.065 mm
  • b)
    0.055 mm
  • c)
    0.045 mm
  • d)
    0.075 mm
Correct answer is option 'C'. Can you explain this answer?

Pritam Kapoor answered
Given:
- The flood lamp stretches the wire by 0.18 mm
- The stress is proportional to the strain
To find:
- How much would it have stretched if the wire had the same length but twice the diameter

Let's begin by understanding the given information.

Stress is defined as the force per unit area and is denoted by the symbol σ (sigma). Mathematically, stress is given by:

σ = F / A

where F is the force applied and A is the area over which the force is applied.

Strain is defined as the change in length per unit length and is denoted by the symbol ε (epsilon). Mathematically, strain is given by:

ε = ΔL / L

where ΔL is the change in length and L is the original length.

From the given information, we know that the stress is proportional to the strain. This can be expressed mathematically as:

σ ∝ ε

or

σ = kε

where k is a constant of proportionality.

Now, let's apply this information to the problem at hand.

When the flood lamp is hung from the wire, it exerts a force on the wire which causes it to stretch. Let's assume that the original diameter of the wire is d and the original length is L.

From the given information, we know that the stress is proportional to the strain. Therefore, we can write:

σ = kε

where σ is the stress, k is a constant of proportionality, and ε is the strain.

The stress can be calculated using the formula:

σ = F / A

where F is the force applied and A is the cross-sectional area of the wire.

The force applied is the weight of the flood lamp, which can be calculated using the formula:

F = mg

where m is the mass of the flood lamp and g is the acceleration due to gravity.

The cross-sectional area of the wire can be calculated using the formula:

A = πd^2 / 4

where d is the diameter of the wire.

Therefore, we can write:

σ = (mg) / (πd^2 / 4)

The strain can be calculated using the formula:

ε = ΔL / L

where ΔL is the change in length and L is the original length.

From the given information, we know that the flood lamp stretches the wire by 0.18 mm. Therefore, we can write:

ε = 0.18 / L

Now, let's combine the equations for stress and strain:

σ = kε

σ = (mg) / (πd^2 / 4)

ε = 0.18 / L

Substituting the values of σ and ε, we get:

(mg) / (πd^2 / 4) = k (0.18 / L)

Simplifying, we get:

k = (mgL) / (0.18πd^2)

Now, let's use this value of k to calculate the change in length when the diameter of the wire is doubled.

When the diameter of the wire is doubled, the cross-sectional area of the wire becomes 4 times the original area. Therefore, the new diameter is 2d and the new cross-sectional area is:

A' = π(2d)^2 / 4 = 4πd^2

Using the same formula for stress,

Select the incorrectly matched pair with regard to the C4 cycle.​
  • a)
    Primary CO2 fixation product – PGA
  • b)
    C4 plant – Maize
  • c)
    Primary CO2 acceptor – PEP
  • d)
    Site of initial carboxylation – Mesophyll cells
  • e)
    Location of enzyme RuBisCO – Bundle sheath cells
Correct answer is option 'A'. Can you explain this answer?

Vignesh answered
The primary CO
fixation product in C
plants is oxaloacetic acid, which is converted to malic acid or aspartic acid that is transported to the bundle sheath cells where the acid is decarboxylated and the CO
thus released enters the Calvin cycle.

What diameter should a 10-m-long steel wire have if we do not want it to stretch more than 0.5 cm under a tension of 940 N? Take Young's modulus of steel as 20 × 1010 Pa
  • a)
    3.2 mm
  • b)
    3.0 mm
  • c)
    3.4 mm
  • d)
    3.6 mm
Correct answer is option 'C'. Can you explain this answer?

Rajesh Gupta answered
Y=F x l/A x Δ l
Δ l=0.5cm=0.5x10-2m, l=10M, F=940N
Y=20x1010pa
20x1010=940x10/πr2x0.5x10-10
πr2=94x100/5x10-3x2x1011=94x102/10x108
r2=94/π x 10-7 =2.99 x 10-6
r2 ≅3x10-6
r=1.13x10-10 m
diameter=2r=3.6mm

With reference to figure the elastic zone is
  • a)
    BC
  • b)
    CD
  • c)
    AB
  • d)
    OA
Correct answer is option 'D'. Can you explain this answer?

Hansa Sharma answered
Hooke’s law: a law stating that the strain in a solid is proportional to the applied stress within the elastic limit of that solid.
In the OA line Hooke’s law is valid because stress is directly proportional to strain.

The S.I unit of stress is
  • a)
    Watt
  • b)
    Joule
  • c)
    Pascal
  • d)
    Newton
Correct answer is option 'C'. Can you explain this answer?

Krishna Iyer answered
Stress has its own SI unit called the Pascal. 1 Pascal (Pa) is equal to 1 N/m2. In imperial units stress is measured in pound force per square inch which is often shortened to "psi". The dimension of stress is same as that of pressure.

Elasticity is the property of a body, by virtue of which
  • a)
    it remains in original size and shape when the force is applied
  • b)
    it changes size and shape when the force is applied and stays in that shape when applied force is removed
  • c)
    it tends to regain its original size and shape when the applied force is removed
  • d)
    it is distorted or stretches without the application of force
Correct answer is option 'C'. Can you explain this answer?

Lavanya Menon answered
Explanation:When external force is applied on the solid bodies, the solid bodies get deformed. The atoms or molecules are displaced from their equilibrium positions causing a change in the interatomic ( or intermolicular ) distances. When the deforming foce is removed, the interatomic forces tend to drive them back to their original postions. Thus the body regains its original shape and size.

Equilibrium can be attained i
  • a)
    all types of system
  • b)
    closed system
  • c)
    open system
  • d)
    isolated system
Correct answer is option 'B'. Can you explain this answer?

Preeti Iyer answered
The equilibrium state can only be reached if the chemical reaction takes place in a closed system. Otherwise, some of the products may escape, leading to the absence of a reverse reaction. (Note that in the diagrams under "Characteristics of Chemical Equilibrium," all reactions are in closed systems.)

Can you explain the answer of this question below:

Equilibrium reactions are found in large scale in production of

  • A:

    ammonia

  • B:

    sulfuric acid

  • C:

    lactic acid

  • D:

    both A and B

The answer is d.

Shreya Gupta answered
An understanding of equilibrium is important in the chemical industry. Equilibrium reactions are involved in some of the stages in the large-scale production of ammonia, sulfuric acid and many other chemicals. 

In photorespiration, the cell organelles involved are
  • a)
    Chloroplast and mitochondrion
  • b)
    Chloroplast, mitochondrion and ribosome
  • c)
    Chloroplast only
  • d)
    Chloroplast, mitochondrion and peroxisome
Correct answer is option 'D'. Can you explain this answer?

Imk Pathsala answered
This process occurs when the concentration of oxygen increase and carbon dioxide decrease and its substrate is glycolate. RubisCO, catalase (CAT) and GOX, and GDC are the main enzymes in chloroplasts, leaf peroxisomes, and mitochondria from mature leaves, respectively, and support the major role of the photorespiratory C2 cycle in leaf metabolism.
So the correct option is 'Mitochondria, peroxisomes and chloroplasts'.

Chloroplast dimorphism is a characteristic feature of​
  • a)
    C4 plants
  • b)
    All plants
  • c)
    Only in algae
  • d)
    Plants with the Calvin cycle
Correct answer is option 'A'. Can you explain this answer?

Jyoti Kapoor answered
The leaves of C4 plants have a characteristic anatomy consisting of concentric bundle sheath and mesophyll cell layers around the vascular bundles. These two distinct cell layers possess chloroplasts which have either structural or size dimorphism.

volume strain is defined
  • a)
    as the change in volume ΔV
  • b)
    as the ratio of change in volume (ΔV) to the original volume V
  • c)
    as the ratio of change in volume (ΔV) to thrice the original volume V
  • d)
    as the ratio of change in volume (ΔV) to twice the original volume V
Correct answer is option 'B'. Can you explain this answer?

Ameya Unni answered
Understanding Volume Strain
Volume strain is an important concept in mechanics and materials science that describes how a material deforms when subjected to external forces.
Definition of Volume Strain
- Volume strain is defined specifically as the ratio of the change in volume (ΔV) to the original volume (V0) of a material.
- Mathematically, it can be expressed as: Volume Strain = ΔV / V0.
Why Option B is Correct
- Change in Volume (ΔV): This represents the difference between the final volume after deformation and the initial volume before deformation.
- Original Volume (V0): This is the volume of the material before any external forces have been applied.
- Ratio Significance: By taking the ratio of the change in volume to the original volume, we obtain a dimensionless quantity that allows for comparison across different materials and conditions.
Other Options Explained
- Option A (Change in Volume V): This does not provide a comparative metric and lacks the necessary context of the original volume.
- Option C (Thrice the Original Volume): This is an arbitrary scaling that does not conform to the standard definition of volume strain.
- Option D (Twice the Original Volume): Similar to Option C, this does not reflect the true relationship defined in mechanics.
Conclusion
In conclusion, volume strain is fundamentally about understanding how a material's volume changes relative to its original volume, which is effectively captured by Option B. This definition is crucial for engineers and scientists to assess material behavior under stress.

Rectangular section is rarely used in beams because
  • a)
    stresses are uniform in a rectangular section
  • b)
    more material in kilos is required
  • c)
    stresses are always plastic in rectangular section
  • d)
    less material in kilos is required
Correct answer is option 'B'. Can you explain this answer?

Anjali Iyer answered
I section is generally used as a beam because of its high section modulus as it's most of the area is situated away from it's neutral axis hence it has high moment of inertia i.e high section modulus i.e high moment carrying capacity which is the major requirement for a good beam section.

The Bundle sheath cells are rich in -------- while lacks----.
  • a)
    RuBisCo, PEPCase
  • b)
    PEPCase, RuBisCo
  • c)
    ATPase, Hydrolase
  • d)
    Hydrolase, ATPase
Correct answer is option 'A'. Can you explain this answer?

EduRev NEET answered
The Bundle sheath cells are rich in RuBisCo while lacks PEPCase.

- RuBisCo: Enzyme responsible for carbon fixation in the Calvin cycle.
- PEPCase: Enzyme involved in C4 photosynthesis, found in mesophyll cells.

In C4 plants, Bundle sheath cells possess RuBisCo for the Calvin cycle, while PEPCase is located in mesophyll cells where initial carbon fixation occurs. This spatial separation enhances efficiency by concentrating CO2 for RuBisCo in Bundle sheath cells.

Which of these is true regarding carbon dioxide fixation?
  • a)
    3 molecules of 2PGA are formed
  • b)
    RuBisCO combines with CO2
  • c)
    RuBP and CO2 give PGA
  • d)
    RuBP acts as a catalyst
Correct answer is option 'C'. Can you explain this answer?

Shilpa Basak answered
Carbon Dioxide Fixation:
Carbon dioxide fixation is the process by which carbon dioxide (CO2) is converted into organic compounds during photosynthesis. It occurs in the Calvin cycle, which is the second stage of photosynthesis. The fixation of carbon dioxide is essential for the production of glucose and other organic molecules.

Ribulose-1,5-bisphosphate (RuBP):
RuBP is a 5-carbon molecule that acts as a starting material in the Calvin cycle. It combines with carbon dioxide in the presence of an enzyme called RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) to form an unstable 6-carbon compound.

Formation of 3-phosphoglycerate (3PGA):
3 molecules of 2-phosphoglycerate (2PGA) are formed:
The unstable 6-carbon compound formed by the combination of RuBP and CO2 immediately breaks down into two 3-carbon molecules called 3-phosphoglycerate (3PGA). This is achieved through a process known as carbon dioxide fixation.

Role of RuBisCO:
RuBisCO combines with CO2:
RuBisCO is the enzyme responsible for catalyzing the reaction between RuBP and CO2. It combines with carbon dioxide and facilitates its attachment to the RuBP molecule. This process is known as carboxylation.

RuBP acts as a catalyst:
Although RuBisCO is the catalyst for the reaction, RuBP itself does not act as a catalyst. It is a reactant that reacts with carbon dioxide to form an unstable compound, which is then converted into 3PGA. However, RuBP is essential for the regeneration of RuBisCO during the Calvin cycle.

Summary:
- Carbon dioxide fixation is the process by which carbon dioxide is converted into organic compounds during photosynthesis.
- Ribulose-1,5-bisphosphate (RuBP) is a 5-carbon molecule that combines with carbon dioxide in the presence of the enzyme RuBisCO.
- The combination of RuBP and CO2 forms an unstable 6-carbon compound, which immediately breaks down into two 3-carbon molecules called 3-phosphoglycerate (3PGA).
- RuBisCO combines with carbon dioxide and acts as a catalyst for the reaction, while RuBP is a reactant that participates in the formation of 3PGA.
- Option C is correct because RuBP and CO2 give rise to 3PGA during carbon dioxide fixation.

Columns are loaded in
  • a)
    shear
  • b)
    hydraulic stress
  • c)
    tension
  • d)
    compression
Correct answer is option 'D'. Can you explain this answer?

Madhavan Patel answered
Alternation of generations (also known as metagenesis) is the type of life cycle that occurs in those plants and algae in the Archaeplastida and the Heterokontophyta that have distinct sexual haploid and asexual diploid stages.

A perfectly rigid body is one
  • a)
    whose shape and size change on application of force
  • b)
    which does not move on application of force
  • c)
    which starts flowing like water on application of force
  • d)
    whose shape and size do not change on application of force
Correct answer is option 'D'. Can you explain this answer?

Arka Bose answered
Explanation:A perfectly rigid body is hypothetical in nature but for some phenomena ( in rotational bodies ) we assume bodies are perfectly rigid i.e. the intermolecular forces are always in equilibrium irrespective of the external forces due to which their shape and size are constant.

At dynamic equilibrium the concentration of  the reactants and products are ____________
  • a)
    equal
  • b)
    sometimes equal sometimes not equal
  • c)
    cannot predict
  • d)
    remain constant
Correct answer is option 'D'. Can you explain this answer?

Ciel Knowledge answered
Understanding Dynamic Equilibrium
  • Dynamic equilibrium refers to a state of balance achieved by two processes occurring at the same rate. In the context of chemical reactions, it describes a condition where the rate of the forward reaction is equal to the rate of the backward reaction.
  • At dynamic equilibrium, the concentrations of the reactants and products do not change because the rates of the forward and backward reactions are the same. This is a state of balance, but not necessarily a state of equality.
Difference in Concentrations of Reactants and Products
  • The concentrations of reactants and products at dynamic equilibrium are not necessarily equal. They are constant, but not necessarily the same.
  • The relative concentrations of the reactants and products at equilibrium depend on the specifics of the reaction, including the equilibrium constant.
  • The equilibrium constant, represented as K, is the ratio of the concentrations of the products to the reactants at equilibrium. If K is greater than 1, the concentration of the products is greater than the reactants at equilibrium. If K is less than 1, the concentration of the reactants is greater than the products at equilibrium.
Conclusion
So, the correct answer is d. remain constant. At dynamic equilibrium, the concentration of the reactants and the products are constant. 

Kranz anatomy is one of the characteristics of the leaves of
  • a)
    Wheat
  • b)
    Sugarcane
  • c)
    Mustard
  • d)
    Potato
Correct answer is option 'B'. Can you explain this answer?

Sameer Ansari answered
Kranz anatomy is found in chloroplasts of c4 plants like sugarcane the have photosynthetic cell arranged in a special used manner.these are bundle sheath cells that surrounds the vascular centers and mesophyll cells that in turn surrounds the buny sheath cells.Rubisco is localised only within the interliased bundle sheath cells that help in carbon fixation.

At which of the following temperatures water is a dynamic equilibrium with ice?
  • a)
    0 Kelvin
  • b)
    100 Kelvin
  • c)
    zero degree Fahrenheit
  • d)
    zero degree centigrade
Correct answer is option 'D'. Can you explain this answer?

  • Water is a dynamic equilibrium with ice at the freezing point of water that is zero degrees centigrade, 273 Kelvin and 32-degree Fahrenheit.
  • Because at zero degrees centigrade the phase transition occurs.

Elastomers are materials
  • a)
    which can be stretched without corresponding stress
  • b)
    which cannot be stretched to cause large strains
  • c)
    which cannot be stretched to beyond elastic limit
  • d)
    which can be stretched to cause large strains
Correct answer is option 'D'. Can you explain this answer?

Rajeev Saxena answered
An elastomer is a polymer with viscoelasticity (i. e., both viscosity and elasticity) and very weak intermolecular forces, and generally low Young's modulus and high failure strain compared with other materials. Elastomer rubber compounds are made from five to ten ingredients, each ingredient playing a specific role. Polymer is the main component, and determines heat and chemical resistance, as well as low- temperature performance. Reinforcing filler is used, typically carbon black, for strength properties.

A circular steel wire 2.00 m long must stretch no more than 0.25 cm when a tensile force of 400 N is applied to each end of the wire. What minimum diameter is required for the wire?  Given that the Young's modulus for steel is Young's modulus of the material is 2.00×1011 N/m2)
  • a)
    1.4 mm
  • b)
    10 mm
  • c)
    1.5 mm
  • d)
    12.4 mm
Correct answer is option 'A'. Can you explain this answer?

Swati Chauhan answered
Understanding the Problem
To determine the minimum diameter required for a circular steel wire, we must consider the relationship between tensile stress, strain, and Young's modulus.
Key Given Data:
- Length of wire (L) = 2.00 m
- Maximum stretch (ΔL) = 0.25 cm = 0.0025 m
- Tensile force (F) = 400 N
- Young's modulus for steel (E) = 2.00 × 10^11 N/m²
Formulas to Use:
1. Strain (ε): ε = ΔL / L
2. Stress (σ): σ = F / A
3. Young's Modulus (E): E = σ / ε
Calculating Strain:
- Strain (ε) = ΔL / L
- ε = 0.0025 m / 2.00 m = 0.00125
Calculating Stress:
Using Young's modulus, we can rearrange the formula to find stress:
- σ = E × ε
- σ = (2.00 × 10^11 N/m²) × (0.00125) = 2.5 × 10^8 N/m²
Finding the Required Area:
From the stress formula, we can find the cross-sectional area (A):
- A = F / σ
- A = 400 N / (2.5 × 10^8 N/m²) = 1.6 × 10^-6 m²
Calculating Diameter:
The area of a circle is given by A = (π/4) × d². Rearranging gives:
- d² = (4A) / π
- d = √((4 × 1.6 × 10^-6 m²) / π)
- d ≈ 0.0014 m = 1.4 mm
Conclusion:
The minimum diameter required for the wire is 1.4 mm, confirming option 'A' as the correct answer.

In which of the following conditions do you think the rates of both forward and backward reactions are the same?
  • a)
    unstable equilibrium
  • b)
    not in an equilibrium
  • c)
    equilibrium
  • d)
    the beginning of a reaction
Correct answer is option 'C'. Can you explain this answer?

In a chemical reaction a state comes when both the forward and reverse reactions occur at the same rate and this state is known as equilibrium.
  • At the beginning of the reaction, the rate of the Forward reaction is higher than the rate of backward reaction.

A piece of copper having a rectangular cross-section of 15.2 mm × 19.1 mm is pulled in tension with 44,500 N force, producing only elastic deformation. Calculate the resulting strain? Take Young's modulus of copper as 42 × 10
9
Pa
  • a)
    3.65 × 10-8
  • b)
    3.65 × 10-3
  • c)
    3.65 × 10-9
  • d)
    3.65 × 10-2
Correct answer is option 'B'. Can you explain this answer?

Anjana Sharma answered
Given Data,
Length of the piece of copper = l = 19.1 mm = 19.1 × 10-3m
Breadth of the piece of copper = b = 15.2 mm = 15.2× 10-3m
Tension force applied on the piece of cooper, F = 44500N
Area of rectangular cross section of copper piece,
Area = l× b
⇒ Area = (19.1 × 10-3m) × (15.2× 10-3m)
⇒ Area = 2.9 × 10-4 m2
Modulus of elasticity of copper from standard list, η = 42× 109 N/m2
By definition, Modulus of elasticity, η = stress/strain

⇒ Strain = F/Aη

⇒ Strain = 3.65 × 10-3
Hence, the resulting strain is 3.65 × 10-3

Complete the reaction.
RuBP + CO2 →
  • a)
    2 × 3PGA
  • b)
    3 × 3PGA
  • c)
    2 × 3PGA + RuBisCO
  • d)
    3 × 3PGA + RuBisCO
Correct answer is option 'A'. Can you explain this answer?

Imk Pathsala answered
  • The given reaction is that of the first step of the Calvin cycle, carbon dioxide fixation.
  • RuBP combines with carbon dioxide to form two molecules of 3PGA. RuBisCO is an enzyme that catalyses the reaction.

Stress is
  • a)
    force per unit length
  • b)
    force per unit area
  • c)
    total applied force
  • d)
    three point average of forces
Correct answer is option 'B'. Can you explain this answer?

Yash Unni answered
The Explanation:

Stress is defined as the force per unit area. It is a measure of how much force is being applied to a given area. Stress can be experienced by objects or materials when an external force is applied to them.

Force per Unit Area:
Stress is calculated by dividing the force applied on an object or material by the area over which the force is applied. It represents the intensity of the force distributed over the surface area. The formula for stress is:

Stress = Force / Area

Types of Stress:
There are different types of stress based on the type of forces applied. Some of the common types of stress include:

1. Tensile Stress: This type of stress occurs when a material is being stretched or pulled apart. It is represented by a positive value.

2. Compressive Stress: This type of stress occurs when a material is being compressed or pushed together. It is represented by a negative value.

3. Shear Stress: This type of stress occurs when a material is being subjected to forces parallel to its surface.

4. Bending Stress: This type of stress occurs when a material is being bent or subjected to bending forces.

Significance of Stress:
Stress is an important concept in engineering and materials science. It helps engineers and scientists understand how materials behave under different conditions and forces. By studying stress, they can design structures and materials that can withstand the expected forces and loads.

Measurement of Stress:
Stress can be measured using different instruments such as strain gauges, load cells, and pressure sensors. These instruments measure the applied force and the area over which the force is distributed.

Relation to Option 'B':
Option 'B' states that stress is the force per unit area, which is the correct definition of stress. Stress is not the force per unit length (Option 'A'), total applied force (Option 'C'), or the three-point average of forces (Option 'D).

In conclusion, stress is the force per unit area and is an important concept in engineering and materials science. It helps in understanding how materials respond to external forces and is measured using various instruments.

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