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How is power related to time?
- A. Power is inversely proportional to time
- B. Power is directly proportional to time
- C. Power is unrelated to time
- D. Power is the product of time and work
Correct Answer: C
Rationale: Power is a measure of how quickly work is done or energy is transferred. It is defined as the rate at which work is done or energy is transferred. Power is not directly or inversely proportional to time, as it depends on the amount of work done or energy transferred, not the duration over which it is done. The relationship between power and time is not a direct one, so power is unrelated to time. Choice A and B are incorrect because power's relationship with time is not one of direct or inverse proportionality. Choice D is incorrect because power is not simply the product of time and work; it is the rate at which work is done or energy is transferred, which can vary independently of time.
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Which mineral is essential for muscle function and nerve transmission?
- A. Calcium
- B. Iron
- C. Sodium
- D. Potassium
Correct Answer: D
Rationale: Potassium is the correct answer as it is essential for muscle function and nerve transmission. Potassium plays a crucial role in regulating muscle contractions, including the heart's beating, and is vital for transmitting electrical signals within the nervous system. Calcium (Choice A) is important for muscle contraction but is not the primary mineral for nerve transmission. Iron (Choice B) is important for oxygen transport in the blood. Sodium (Choice C) is important for fluid balance but is not primarily responsible for muscle function and nerve transmission.
In the reaction 2Na + 2H2O → 2NaOH + H2, what is the limiting reactant when 3 moles of sodium react with 2 moles of water?
- A. Na
- B. H2O
- C. NaOH
- D. H2
Correct Answer: A
Rationale: The balanced chemical equation indicates that 2 moles of sodium react with 2 moles of water to yield 2 moles of sodium hydroxide and 1 mole of hydrogen gas. When 3 moles of sodium react with only 2 moles of water, sodium becomes the limiting reactant as it is present in excess compared to the available water molecules. This situation arises because not all sodium atoms can fully react with the limited amount of water, resulting in sodium being the limiting reactant in this specific case. Choice B (H2O), choice C (NaOH), and choice D (H2) are incorrect as they are not the limiting reactant in the given reaction scenario.
When you push a book across a table, the book experiences an equal and opposite force from the table. Why doesn't the table move as well?
- A. The table is much heavier than the book.
- B. The force on the book acts in a different direction.
- C. The table has a much larger surface area, distributing the force over a wider area.
- D. All of the above
Correct Answer: A
Rationale: The table is much heavier than the book, so it requires a much larger force to accelerate it. The book is lighter and easier to move, so the force applied to it causes it to move without significantly affecting the table due to the table's greater mass. Newton's third law states that for every action, there is an equal and opposite reaction. In this case, the force exerted on the book by the table is countered by an equal force exerted on the table by the book, but the table's greater mass resists movement. Choice B is incorrect because the forces are equal and opposite, acting in the same direction. Choice C is incorrect as the surface area does not affect the movement of the table in this scenario. Therefore, the correct answer is A, as the table's greater mass prevents it from moving easily when a force is applied.
What is the difference between exhalation (expiration) and inhalation (inspiration)?
- A. Exhalation involves active muscle contraction, while inhalation is passive.
- B. Inhalation brings in oxygen-rich air, while exhalation releases carbon dioxide-rich air.
- C. Exhalation occurs through the nose only, while inhalation can occur through the nose or mouth.
- D. Inhalation warms and humidifies air, while exhalation cools and dries air.
Correct Answer: A
Rationale: Exhalation (expiration) involves active muscle contraction, specifically the diaphragm and intercostal muscles, to decrease the volume of the thoracic cavity and push air out of the lungs. In contrast, inhalation (inspiration) is a passive process where the diaphragm and external intercostal muscles contract to increase the thoracic cavity volume, allowing air to flow into the lungs. Choice B is incorrect as exhalation removes carbon dioxide-rich air and inhalation brings in oxygen-rich air. Choice C is incorrect because both exhalation and inhalation can occur through the nose or mouth. Choice D is inaccurate as inhalation humidifies and warms the air, while exhalation cools and dries it.
Vacuoles are large sacs for storage in plant cells. What is their main function in animal cells?
- A. Protein synthesis
- B. Waste storage and disposal
- C. Photosynthesis
- D. Cellular respiration
Correct Answer: B
Rationale: Vacuoles in animal cells primarily function in waste storage and disposal, helping to maintain cellular homeostasis by storing waste products and aiding in their removal from the cell. Unlike plant cells, animal cells do not typically use vacuoles for storage purposes such as water, nutrients, or pigments. Instead, animal cells rely on other organelles like lysosomes for waste management and maintaining cellular balance. Choices A, C, and D are incorrect because protein synthesis occurs in ribosomes, photosynthesis takes place in chloroplasts (absent in animal cells), and cellular respiration mainly occurs in mitochondria, respectively. Vacuoles in animal cells serve a different purpose compared to plant cells.