Mathematics and Science PYQs

The correct answer is gravitational force & air resistance

Concept:

• When a ball is thrown vertically upwards in the air, it is acted upon by two forces: the gravitational force and the force of air resistance.
• The gravitational force is always pulling the ball down towards the Earth, while the force of air resistance is opposing the motion of the ball. The force of air resistance depends on the speed of the ball and the density of the air.
• The force of propulsion exerted by the thrower is only present for a short period of time when the ball is being thrown. Once the ball is released, the only forces acting on it are the gravitational force and the force of air resistance.

Explanation:

• Gravitational force: The gravitational force is the force that pulls all objects towards the center of the Earth. The gravitational force is proportional to the mass of the object and the mass of the Earth.
• The gravitational force between the Earth and a ball is very strong, so it is the main force that causes the ball to fall back to the Earth.
• Air resistance: Air resistance is the force that opposes the motion of objects through the air. Air resistance is caused by the friction between the air molecules and the surface of the object.
• The force of air resistance is proportional to the speed of the object and the density of the air.
• The force of air resistance increases as the speed of the object increases.
• Force of propulsion: The force of propulsion is the force that is exerted on an object by the person or thing that is throwing it. The force of propulsion is usually applied for a short period of time, and it is usually much smaller than the gravitational force.

The correct answer is (i) diabetes (ii) pancreas (iii) insulin.

Explanation:

• Diabetes: Insufficient production or ineffective utilization of insulin by the body leads to a condition called diabetes. In diabetes, the person may have high blood sugar levels, and the body may not be able to properly regulate glucose.
• Pancreas: The pancreas is both an exocrine and endocrine gland in human beings. It has specialized cells called Islets of Langerhans that produce hormones.
• Insulin: The pancreas produces insulin hormone. Insulin plays a crucial role in regulating blood sugar levels by allowing cells to take in glucose from the bloodstream.

The Correct answer is Vinegar, lemon juice, gastric juice, curd.

Concept:

• Acids are substances that release hydrogen ions (H⁺) in solution. This makes the solution more acidic, with a lower pH. The pH scale ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic, and a pH above 7 is basic.

Explanation:

• Vinegar, lemon juice, gastric juice, and curd are all acidic substances. Vinegar is a solution of acetic acid in water. Lemon juice is a solution of citric acid in water. Gastric juice is a solution of hydrochloric acid in water. Curd is a dairy product that is high in lactic acid.
• Baking soda, shampoo, and toothpaste are all basic substances. Baking soda is a solution of sodium bicarbonate in water. Shampoo is a solution of various alkaline substances in water. Toothpaste is a paste that contains abrasives, fluoride, and flavoring agents.
• Calamine lotion is a mixture of zinc oxide and water. It is used to treat skin irritations. Calamine lotion is not acidic or basic.

Therefore, the only set of substances that are acidic in nature are vinegar, lemon juice, gastric juice, and curd.

The Correct answer is Both (A) & (R) are true and (R) is the correct explanation of (A).

Concept:

• Diffusion is the process by which molecules of a substance spread out evenly throughout a space. This happens because the molecules are constantly moving and colliding with each other. The faster the molecules move, the faster they will diffuse.

Explanation:

• The particles of a gas are very small and have a lot of kinetic energy. This means that they move about very quickly and collide with each other very often. When a gas is introduced into another gas, the particles of the first gas will collide with the particles of the second gas and spread out evenly throughout the space. This is called diffusion.
• The faster the particles of a gas move, the faster they will diffuse. Therefore, the statement that gases diffuse very fast into other gases is correct because the particles of a gas move about at high speed.
• The reason for the statement is also correct. The particles of a gas move about at high speed because they have a lot of kinetic energy.
• This kinetic energy is due to the temperature of the gas. The higher the temperature of a gas, the faster the particles will move. Therefore, the statement that gas particles move about at high speed is correct because the kinetic energy of the particles is due to the temperature of the gas.

The Correct answer is Only (C).

Concept:

Chemical changes

• If the chemical composition of a product is changing then it is a chemical change.
• The changes are irreversible change.
• And the final product is different from the initial one.
• Example of chemical changes is the burning of a candle, the ripening of fruit, the curdling of milk, and the digestion of food etc.

Physical changes

• if the chemical composition is remaining the same but only the state changes, then it is a physical change.
• The changes are reversible changes.
• The state changes but the final products are the same as the initial one.
• Example of physical changes is the Freezing of water and Evaporation of water etc.

Explanation:

• (A) Burning of wood is a chemical change because it involves a chemical reaction where the wood undergoes combustion and reacts with oxygen to produce heat, light, and new chemical compounds like carbon dioxide and water vapor.
• It is also an irreversible change because the original wood cannot be recovered.
• (B) Boiling of water is a physical change, not a chemical change. It involves the conversion of liquid water into water vapor due to the input of heat energy. Boiling is a reversible change because when the vapor cools down, it condenses back into liquid water.
• (C) Grinding wood into sawdust is a physical change because it only involves a change in the physical state or size of the wood particles.
• The chemical composition of the wood remains the same. Grinding wood into sawdust is also an irreversible change because the original wood cannot be restored to its original form.

The Correct answer is (A) & (B).

Explanation:

• An object that floats in alcohol will surely float in sunflower oil: this is correct because alcohol is less dense than sunflower oil.
• If an object is less dense than the liquid it is in, it will float. Since alcohol is less dense than sunflower oil, an object that floats in alcohol will also float in sunflower oil.
• An object that floats in sunflower oil will surely float in freshwater: This is also correct because sunflower oil is less dense than freshwater.
• If an object is less dense than the liquid it is in, it will float. Since sunflower oil is less dense than freshwater, an object that floats in sunflower oil will also float in fresh water.
• An object that floats in freshwater will surely float in alcohol. This is not necessarily correct because alcohol is more dense than fresh water.
• If an object is less dense than the liquid it is in, it will float. However, if an object is more dense than the liquid it is in, it will sink. Therefore, an object that floats in freshwater may not necessarily float in alcohol.

Therefore, the correct statements are (A) and (B).

The Correct answer is 

Calculation:

Average Speed = Total distance/ Total time

distance between Kanpur & Bangalore = 2182 km.

Starting time: 1^st September at 15 ∶ 50 hours and reaches Bangalore on 3^rd September at 07 ∶ 10 hours. 

Total Time = 39 hours + (20 minutes / 60) hours = 39.33 hour

Average Speed = 2182 km / 39.33 hours ≈ 55.44 km/h

Therefore, the average speed of the train is approximately 55.44 km/h ≈ 55.5 km/h

The Correct answer is Antibodies, vaccine, tuberculosis.

Explanation:

• When a disease-carrying microbe enters our body**, the body produces antibodies to fight the invader.**  Antibodies are produced as a response to the presence of pathogens in the body.
• If dead or weakened microbes are introduced into a healthy body, the body fights and kills them, producing these. This refers to the production of antibodies in response to the introduction of vaccines, which contain dead or weakened microbes.
• Vaccines stimulate the immune system to produce antibodies that provide immunity against specific diseases.
• This is how a vaccine works to prevent diseases like tuberculosis.
• Tuberculosis is a bacterial infection, and vaccination against tuberculosis is a common preventive measure to reduce the risk of developing the disease.

Therefore Antibodies, vaccine, and tuberculosis, correctly fill the blanks in the given order.

The Correct answer is Rayon.

Explanation:

• Rayon is a manufactured regenerated cellulosic fiber derived from wood pulp. It is a semi-synthetic fiber, meaning that it is made from a natural source (wood pulp) but is processed using chemical methods.
• It is a soft and absorbent fiber that is often used to make clothing, bedsheets, and towels.
• Acrylic is a synthetic fiber made from petroleum. It is a versatile fiber that can be used to make a variety of fabrics, including sweaters, fleece, and carpets.
• Nylon is a synthetic fiber made from petroleum. It is a strong and durable fiber that is often used to make clothing, ropes, and carpets.
• Polyester is a synthetic fiber made from petroleum. It is a strong and wrinkle-resistant fiber that is often used to make clothing, sheets, and upholstery.

The Correct answer is (B) & (C).

Concept:

• Petroleum is a naturally occurring liquid fossil fuel that is found beneath the Earth's surface. It is a complex mixture of hydrocarbons, which are organic compounds consisting of carbon and hydrogen atoms.

Explanation:

CNG (compressed natural gas):

• CNG is primarily composed of methane gas. It is obtained from natural gas reserves and not from petroleum. Natural gas is extracted from underground reservoirs and can be compressed to form CNG, which is used as fuel for vehicles and other applications.

LPG (liquefied petroleum gas):

• LPG is a mixture of hydrocarbon gases, primarily propane and butane. It is obtained during the refining of petroleum. LPG is commonly used as fuel for heating, cooking, and powering vehicles.

Diesel:

• Diesel fuel is a type of liquid fuel commonly used in diesel engines, such as those found in cars, trucks, and generators. It is obtained from crude oil during the refining process.
• Diesel is composed of various hydrocarbons, including alkanes, cycloalkanes, and aromatic hydrocarbons.

Coal gas:

• Coal gas, also known as town gas, is a flammable gas produced by the destructive distillation of coal.
• It was used as a fuel for heating and lighting in the past, but it is no longer a common source of energy. Coal gas is distinct from petroleum and is derived from coal rather than petroleum reserves.

LPG and diesel are obtained from petroleum, while CNG and coal gas are obtained from natural gas and coal, respectively.

Open book tests are designed to assess higher order thinking rather than rote memorisation. They focus on understanding, application, analysis, and problem solving by allowing students to refer to books or notes during the examination.

Key Points

• Long derivations of standard formulae are not recommended for an open book test because such questions mainly test memory and mechanical recall.
• Since students already have access to textbooks and notes, reproducing lengthy derivations does not assess understanding or thinking skills. These questions encourage copying rather than interpretation or application.
• Open book tests aim to evaluate how students use information, not how well they can reproduce it. Therefore, asking long standard derivations defeats the core purpose of an open book assessment.

Hint

• Applying theoretical principles to unfamiliar situations promotes transfer of learning and deep understanding.
• Open ended questions allow multiple perspectives and encourage critical thinking.
• Solving innovative problems assesses creativity and analytical ability, which are key goals of open book tests.

Hence, the correct answer is long derivations of standard formulae.

Conducting a group discussion on socio-scientific issues in a science class aims to engage students in critical thinking, analysis, and exploration of complex topics.

Key Points

• The objective is to encourage students to consider diverse perspectives and develop their ability to construct evidence-based arguments.
• However, the goal is not to lead all students to a predetermined correct resolution.
• Socio-scientific issues often involve ethical, social, and scientific considerations, which can have multiple valid perspectives and interpretations.
• Group discussions on these issues provide an opportunity for students to explore different viewpoints, understand the complexity of the topics, and develop their own informed opinions.
• The objective of a group discussion on socio-scientific issues is not to impose a singular correct resolution but to foster open dialogue, respect for diverse opinions, and critical analysis.
• It also allows students to recognize the social context of science, understanding how scientific knowledge intersects with societal values, norms, and decision-making processes.

Hence, it can be concluded that option 3 is the correct answer.

By engaging students in hands-on activities that involve producing sound through vibrations, such as plucking a stretched rubber band, they can directly experience and observe the cause-effect relationship between vibration and sound.

Key Points

• This approach promotes experiential learning, which is highly effective in helping students understand scientific concepts.
• Through the activity, students can feel the vibrations generated by the plucked rubber band and hear the resulting sound.
• This hands-on experience allows them to connect the physical motion of the vibrating rubber band to the sound waves produced.
• It helps in reinforcing the concept that vibrations are responsible for the production of sound.

Hence, it can be concluded that option 1 is the correct answer.

Engaging students in floating and sinking activities would be the most appropriate strategy to introduce the concept of buoyant force. Through these activities, students can directly observe and experience the effects of buoyant force in action.

Key Points

• By manipulating objects of different densities and observing their behavior in water or other fluids, students can see firsthand how objects float or sink.
• They can explore variables such as the weight, shape, and size of the objects to understand how these factors influence the buoyant force exerted by the fluid.
• Engaging in floating and sinking activities allows students to develop a concrete understanding of buoyant force and its relationship with the density of objects and the properties of fluids.
• It promotes hands-on learning and critical thinking as students analyze their observations and make connections between the behavior of objects and the forces acting on them.

Hence, it can be concluded that engaging students in floating and sinking activities is the correct answer.

By comparing cells to bricks in buildings, the teacher is employing an analogy.

Key Points

• An analogy is a pedagogic device that involves drawing similarities between two different things or concepts to help students understand and relate to a new or abstract idea.
• In this case, the teacher is comparing the structural units of living organisms (cells) to the building blocks of structures (bricks).
• The analogy allows students to make connections between familiar concepts (bricks and buildings) and the new concept being introduced (cells).
• It helps students grasp the idea that just as buildings can have different designs, shapes, and sizes despite being made of similar bricks, cells in living organisms can vary in structure and function even though they are composed of similar basic units.

Hence, it can be concluded that analogy is the correct answer.

While science fairs in schools serve various purposes, the least likely purpose to be served through their organization is the identification of specific conceptual difficulties of individual students.

Key Points

• However, identifying specific conceptual difficulties of individual students is not typically the main purpose of organizing science fairs.
• While science fairs may indirectly help identify conceptual difficulties, their primary emphasis is on encouraging creativity, scientific inquiry, and collaborative learning rather than diagnosing individual students' difficulties.
• Identifying specific conceptual difficulties usually occurs through other means, such as classroom assessments, individualized instruction, or one-on-one interactions between teachers and students.
• Science fairs, on the other hand, focus on promoting enthusiasm for science, showcasing student projects, and fostering a collaborative and interactive learning environment.

Hence, it can be concluded that option 4 is the correct answer.

In a scientific experiment, the independent variable is the factor that is deliberately manipulated or varied by the experimenter.

Key Points

• In this experiment, the length of the pendulum is an independent variable because it is the one being manipulated to see if it affects the outcome.
• The period is a dependent variable because it is what the students are measuring and observing to see if it changes in response to alterations in the length of the pendulum.
• Therefore, it would be incorrect to classify the time period as a controlled variable.
• Controlled variables are those that are kept constant throughout the experiment to ensure that they do not influence the results. In this case, the mass of the bob, the angle of displacement (assuming it's not mentioned), etc., would be controlled variables because they are not being changed for the purpose of the experiment.

Hence, it can be concluded that option 2 is the correct answer.

By visiting a bird sanctuary and observing birds in their natural habitat, students can directly observe the correlation between the shapes of beaks and the types of food birds consume.

Key Points

• They can make firsthand observations of birds using their beaks to obtain various types of food, such as probing flowers for nectar, pecking at seeds, or capturing insects.
• This hands-on experience allows students to see the functional adaptations of different beak shapes in action.
• They can draw connections between the unique features of each bird's beak and its specific diet.
• The direct observation of birds' feeding behaviors and interactions with their environment provides a rich learning experience that enhances students' understanding of the relationship between beak shape and feeding habits.

Hence, it can be concluded that option 3 is the correct answer.

Our present understanding of the organization of the science curriculum emphasizes that the science content at the upper primary stage should not be considered a diluted version of secondary school science.

Key Points

• At the upper primary stage, the focus is on laying a strong foundation of scientific concepts and skills.
• It involves engaging students in hands-on activities, exploration, and inquiry-based learning experiences.
• The curriculum should provide a solid base for further learning and understanding of science principles.
• The idea of regarding the upper primary stage science as a diluted version of secondary school science suggests a linear progression of knowledge, where the content is simply watered down.
• However, our present understanding promotes a more progressive and age-appropriate approach to science education, ensuring that students develop a strong conceptual understanding and a positive attitude towards science from the early stages.

Hence, it can be concluded that option 2 is the corrcet answer.

Option 2: (A), (B), (C) are observations; (D) is an inference.

 

Key Points

• "The colour of solution changes from blue to pale green." - This is an observation because it describes a direct change in the color of the solution that can be observed.
• The student can visually perceive the difference in color before and after the reaction between the iron nails and copper sulfate solution.
• "The brown coating gets formed on the iron nails." - This is an observation as it describes the formation of a brown coating on the nails, which can be directly observed.
• The student can see the physical change occurring on the surface of the iron nails.
• "Iron displaces copper from its solution." - This is an observation as it describes the direct observation of iron displacing copper from the solution, indicating a chemical reaction.
• The student can observe the change in the solution as the iron reacts with the copper ions, leading to the displacement of copper.

Hence, it can be concluded that option 2 is the correct answer.