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The correct answer is have same velocity at any instant.

Key Points

• When an object is under free fall, its acceleration depends only on the acceleration due to gravity and mass has no role to play.
• Due to this; irrespective of their masses, the object under free fall with have the same velocity at any instant.
• h=1/2gmt2(u=0)
• t2=2h/gm

The correct answer is by placing the virus in a modified version of a different virus.

Key Points

• Vector vaccines use a harmless virus containing the nucleic acid of a disease-causing virus.
• These modified viruses make antigens inside the host and provide protective immunity against it.

Important Points

• Vector vaccines, also known as viral vector vaccines, work by using a harmless virus to deliver genetic material into the body.
• This genetic material contains instructions to produce a piece of the target pathogen (usually a virus) or a modified version of it, such as a spike protein, which is part of the virus's structure.
• Vector vaccines, like the Oxford-AstraZeneca, Johnson & Johnson's Janssen, and Sputnik V vaccines for COVID-19, have been effective in providing immunity against various diseases.
• They offer several advantages, such as the ability to generate a strong and long-lasting immune response without using live or weakened pathogens, making them safer in some cases.
• Different vector vaccines use various viral vectors and may have distinct mechanisms for delivering the genetic material, but the overall principle of using a harmless virus to trigger an immune response remains consistent.

The correct answer is seafloor spreading.

Key PointsSeafloor Spreading:

• Seafloor spreading is a geologic process in which tectonic plates large slabs of Earth's lithosphere split apart from each other.
• Seafloor spreading and other tectonic activity processes are the result of mantle convection.
• Mantle convection is the slow, churning motion of Earth’s mantle.
• Convection currents carry heat from the lower mantle and core to the lithosphere.
• Convection currents also “recycle” lithospheric materials back to the mantle.
• Seafloor spreading occurs at divergent plate boundaries.
• As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. The less dense material rises, often forming a mountain or elevated area of the seafloor.
• Eventually, the crust cracks. Hot magma fueled by mantle convection bubbles up to fill these fractures and spills onto the crust. This bubbled-up magma is cooled by frigid seawater to form igneous rock. This rock (basalt) becomes a new part of Earth’s crust.
• This process that continually adds new crust to the Earth's surface is called seafloor spreading.
• This geological phenomenon occurs along mid-ocean ridges, which are underwater mountain ranges that run through the world's oceans.

The correct answer is ​the theory of plate tectonics.

Key Points

• The theory that states "pieces of the Earth's crust are in constant, slow motion driven by movement in the mantle" is called Plate Tectonics.
• Plate tectonics is a scientific theory that explains the movement of the Earth's lithospheric plates, which make up the Earth's outer shell.
• These plates float on the semi-fluid asthenosphere beneath them and are driven by the convective currents in the mantle.
• This theory helps explain the formation of continents, ocean basins, earthquakes, volcanic activity, and the interactions of tectonic plate boundaries.

Additional Information

• The theory of plate tectonics is a comprehensive scientific theory that explains the movement of the Earth's lithospheric plates, which make up the Earth's outer shell.
• The theory is composed of several key ideas:
• Lithospheric Plates: The Earth's rigid outer layer, known as the lithosphere, is divided into several large and small plates that "float" on the semi-fluid asthenosphere beneath them.
• Plate Boundaries: The edges of these plates are the most dynamic regions on Earth. There are three primary types of plate boundaries:
• Divergent Boundaries: At divergent boundaries, plates move away from each other. This can lead to the formation of new oceanic crust through seafloor spreading and the creation of rift valleys on continents.
• Convergent Boundaries: At convergent boundaries, plates move toward each other. When two plates collide, it can result in subduction, where one plate is forced beneath the other, leading to the formation of deep ocean trenches, volcanic arcs, and mountain ranges.
• Transform Boundaries: At transform boundaries, plates slide past each other horizontally. The friction and pressure along these boundaries can lead to earthquakes.
• Seafloor Spreading: Harry Hess and Robert Dietz's work in the mid-20^th century contributed to the understanding of seafloor spreading. This process occurs at mid-ocean ridges, where new oceanic crust is formed as magma rises and solidifies.
• Plate Interactions: The interactions of these plates result in various geological features, including the formation of mountain ranges, volcanic activity, earthquakes, and the distribution of continents and oceans.

The correct answer is Messenger Ribonucleic Acid.

Key Points mRNA:

• The term "mRNA" stands for "messenger RNA."
• mRNA is a single-stranded molecule that is complementary to the DNA template strand from which it was transcribed.
• The sequence of nucleotides in the mRNA carries the instructions for the specific sequence of amino acids in a protein.
• Messenger RNA is a type of RNA (ribonucleic acid) molecule that plays a crucial role in the process of protein synthesis within cells.
• During the COVID-19 pandemic, mRNA technology has gained significant attention due to the development of mRNA vaccines, such as the Pfizer-BioNTech and Moderna COVID-19 vaccines.
• These vaccines use synthetic mRNA to instruct cells to produce a modified spike protein found on the surface of the SARS-CoV-2 virus, which triggers an immune response and helps protect against COVID-19.
• The use of mRNA technology in vaccines has been a major breakthrough in the fight against the pandemic.
• During the pandemic mRNA is detected by RT-PCR for diagnosis of disease.

The correct answer is dynamo.

Key Points

• An alternating current (AC) can be produced by a dynamo.
• A dynamo is a device that generates electricity through the use of electromagnetic induction. It consists of a coil of wire that rotates within a magnetic field.
• As the coil of wire rotates, it cuts through the lines of magnetic flux, which induces an alternating current in the wire.
• This process is based on Faraday's law of electromagnetic induction, which states that a change in magnetic flux through a closed loop of wire will induce an electromotive force (emf) in the wire, resulting in an alternating current.
• The direction of the current changes as the coil of wire rotates, leading to an AC output.
• Dynamo generators were commonly used in the past to produce electricity, and they are still used in some applications today, although they have been largely replaced by more efficient and reliable alternators and other AC generators in most modern electrical systems.

The correct answer is ​a vector quantity.

Key Points

• Current density (J) is a vector quantity that represents the distribution of electric current (I) within a conductor or a material.
• It is defined as the current passing through a unit area of a conductor and is typically expressed in units of amperes per square meter (A/m^2) in the International System of Units (SI).
• Mathematically, you can calculate current density using the following formula: J = I / A, Where:
• J is the current density in amperes per square meter (A/m^2).
• I is the electric current in amperes (A) passing through the conductor.
• A is the cross-sectional area in square meters (m^2) through which the current is passing.
• Current density is an important concept in the study of electromagnetism and is often used in situations where you want to understand how the electric current is distributed within a conductor, particularly when dealing with materials that may not have uniform cross-sectional areas.

The correct answer is ​Molecular targets.

Key Points

• The most useful classification of drugs for medicinal chemists is based on molecular targets.
• This classification is based on the target molecules, which are usually biomolecules like carbohydrates, lipids, proteins, and nucleic acids.
• Drugs that target specific biomolecules tend to have better results.
• These drugs possess some common structural features and may have the same mechanism of action on a specific drug target.
• There are other ways to classify drugs as well. For example, drugs can be classified based on their chemical structure, pharmacological effect, or drug action.
• However, the classification based on molecular targets is considered the most useful for medicinal chemists.

Additional InformationCommon examples of molecular targets:

• Receptors: Many drugs work by binding to and modulating the activity of cell surface receptors. For example, beta-blockers target beta-adrenergic receptors in the heart to reduce heart rate and blood pressure.
• Enzymes: Enzymes are proteins that catalyze chemical reactions in the body. Drugs can inhibit or enhance the activity of specific enzymes to regulate biological processes.
• DNA and RNA: Some drugs target nucleic acids. For example, chemotherapy drugs often target the DNA in cancer cells to inhibit their replication.
• Proteins in Disease-Related Pathways: In diseases like cancer, drugs may target specific proteins or pathways that are dysregulated in the disease. For example, drugs like Imatinib target the BCR-ABL fusion protein in chronic myeloid leukemia.

The correct answer is None of the above.

Key Points The rate of a chemical reaction can be influenced by various factors:

• Temperature: Generally, increasing the temperature of a reaction speeds it up, while decreasing it slows it down. This is because higher temperatures provide more energy for reactant molecules to overcome the activation energy barrier.
• Concentration of reactants: Increasing the concentration of reactants typically increases the reaction rate. More reactant molecules or ions are available to collide and react.
• Catalysts: Catalysts are substances that speed up chemical reactions by providing an alternative reaction pathway with a lower activation energy. They do not slow down reactions.
• Surface area: Increasing the surface area of solid reactants (e.g., by grinding them into smaller particles) can speed up reactions by exposing more reactant molecules to each other.
• Pressure (for gases): For gaseous reactions, increasing pressure can increase the reaction rate. This is because higher pressure results in more frequent collisions between gas molecules.
• Inhibitors: Inhibitors are substances that can slow down or even stop chemical reactions. They work by interfering with the normal reaction pathway, often by binding to reactants or catalysts and preventing them from functioning properly.

None of the above options given here slows down the reaction rate.

Additional Information Catalytic promoter:

• In most cases, a catalytic promoter does not slow down the reaction rate; rather, it is intended to increase or enhance the rate of a chemical reaction.
• A catalytic promoter, also known as a promoter or promoter catalyst, is a substance that is added to a catalyst to enhance its activity or selectivity in a chemical reaction.
• A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.

Homogeneous catalyst:

• A homogeneous catalyst promoter is typically added to a reaction to enhance or accelerate the reaction rate, not slow it down.
• Homogeneous catalysts are substances that are in the same phase (usually liquid) as the reactants and products in a chemical reaction.
• They work by providing an alternative reaction pathway with a lower activation energy, making it easier for the reactants to transform into products.

Heterogeneous catalyst:

• Heterogeneous catalyst promoters are substances that are added to a heterogeneous catalyst to enhance its catalytic activity.
• These promoters typically increase the reaction rate and improve the overall efficiency of the catalyst rather than slowing it down.
• Promoters can work in several ways to enhance catalysis:
• Surface Area: Some promoters can increase the surface area of the catalyst, providing more active sites for reactants to adsorb and react.
• Chemisorption: Promoters can form strong chemical bonds with reactants, helping them to adsorb onto the catalyst's surface more readily, which can promote faster reaction kinetics.
• Altering Reaction Mechanism: Promoters can modify the reaction pathway and make it more favorable, reducing energy barriers and, thus, increasing the reaction rate.

The correct answer is central nervous system.

Key Points

• Input and output nerves meet at a structure called the synapse, part of central nervous system.
• The synapse is a specialized junction between two nerve cells (neurons) or between a neuron and a target cell, such as a muscle cell or another neuron.
• At the synapse, information is transmitted from the presynaptic neuron (the input) to the postsynaptic neuron (the output) or target cell.
• This transmission is typically mediated by chemical neurotransmitters that are released from the presynaptic neuron and received by receptors on the postsynaptic neuron or target cell, allowing for the propagation of nerve signals.

Additional Information Central Nervous System (CNS):

The central nervous system (CNS) is a crucial part of the human body responsible for processing and coordinating information from the body's sensory organs and controlling various bodily functions.

It consists of the brain and the spinal cord. Here are some key aspects of the central nervous system:

• Brain:
• The brain is the most complex and vital organ in the CNS.
• It plays a central role in controlling and coordinating various bodily functions, such as thinking, memory, emotions, movement, and sensory perception.
• It is protected by the skull and is divided into different regions, each with specific functions.
• Spinal Cord:
• ​The spinal cord is a long, thin, tubular structure that extends from the brain down the vertebral column.
• It serves as a bridge between the brain and the rest of the body, carrying signals to and from the brain.
• The spinal cord is responsible for reflex actions and relaying sensory and motor information.
• Neurons:
• Neurons are the functional units of the CNS.
• They are specialized cells that transmit electrical and chemical signals, allowing communication within the nervous system.
• Neurons have dendrites that receive signals, a cell body that processes information, and an axon that transmits signals to other neurons or to muscles and glands.
• White Matter and Gray Matter:
• The brain and spinal cord contain both white matter and gray matter.
• Gray matter consists of neuron cell bodies and synapses and is involved in information processing.
• White matter is composed of myelinated axons that transmit signals over longer distances and connects different regions of the CNS.