What is the definition of 'acceleration' in terms of motion?

Correct Answer: A

Rationale: Acceleration is defined as the rate of change of velocity of an object over time. It represents how an object's velocity is changing, either by speeding up, slowing down, or changing direction. Option B, 'Speed in a straight line,' actually refers to velocity, not acceleration. Option C, 'Distance covered in a given time,' is more related to speed, as it measures how much ground is covered in a specific time period. Option D, 'Force applied to an object,' is not the definition of acceleration; it is a force exerted on an object that can cause acceleration.

Correct Answer: B

Rationale: The correct answer is a Pivot joint. A pivot joint, like the joint in the neck, enables rotational movement around a single axis. This type of joint is crucial for allowing the head to turn from side to side. Choice A, Ball-and-socket joint, allows for movement in multiple axes due to its spherical structure, not limited to single-axis rotation. Choice C, Hinge joint, allows movement in one plane like a door hinge, but not rotational movement around a single axis. Choice D, Saddle joint, allows movement in multiple directions but is not specifically designed for rotational movement around a single axis.

Correct Answer: C

Rationale: According to the Law of Conservation of Energy, the total amount of energy in a closed system remains constant. This principle states that energy cannot be created or destroyed within the system but can only be transformed from one form to another. Therefore, the total energy within the system is conserved and does not change over time. Choice A is incorrect because the total energy in a closed system does not increase over time, as it remains constant. Choice B is incorrect as the total energy does not decrease over time within a closed system. Choice D is incorrect as the conservation of energy is not dependent on the temperature of the system, but rather on the transformation and conservation of energy within the system. Understanding this concept is fundamental for understanding the behavior of energy in various physical systems and processes.

Correct Answer: B

Rationale: The correct answer is B, 'The ability to maintain a stable internal environment.' Homeostasis refers to the body's ability to regulate and maintain a stable internal environment, which includes variables like body temperature, pH levels, and fluid balance. It involves processes that help keep the body's internal conditions within a narrow range, despite external changes. While maintaining body temperature is a component of homeostasis, it is not the complete definition of the term. Choice C, 'The ability to increase body temperature when cold,' is incorrect as homeostasis aims to maintain stability rather than promoting temperature increases in response to external conditions. Choice D, 'The ability to regulate blood glucose levels,' is also incorrect as this is a specific function related to glucose homeostasis, which is a part of overall homeostatic processes but not the sole definition of homeostasis itself.

Correct Answer: C

Rationale: A) Transcribes DNA into mRNA: This is the function of RNA polymerase, not transfer RNA (tRNA). tRNA is involved in protein synthesis, not transcription. B) Decodes the genetic code on mRNA: This is the function of tRNA during translation. tRNA molecules carry specific amino acids and recognize the codons on mRNA, ensuring the correct amino acid is added to the growing polypeptide chain. C) Carries specific amino acids to the ribosomes: This is the primary role of tRNA in protein synthesis. Each tRNA molecule is specific for a particular amino acid and carries it to the ribosome, where it is added to the growing protein chain. D) Modifies the structure of proteins: This is not a function of tRNA. Protein modification can occur after translation is complete and involves other cellular processes and molecules.

Correct Answer: B

Rationale: The correct answer is B: "To absorb nutrients." The small intestine's primary function is to absorb nutrients from digested food. It plays a crucial role in the digestion and absorption of nutrients such as proteins, carbohydrates, fats, vitamins, and minerals, which are essential for the body's functions and energy production. Choice A, "To absorb water," is incorrect because the absorption of water primarily occurs in the large intestine. Choice C, "To store waste," is incorrect as waste is stored in the large intestine before elimination. Choice D, "To produce enzymes," is incorrect because while the small intestine does receive enzymes from other organs to aid in digestion, its primary role is not enzyme production.

Correct Answer: C

Rationale: A) Crypts of Lieberk¼hn are small pits in the lining of the small intestine that contain cells involved in the production of intestinal juices, but they do not increase the surface area for absorption. B) Goblet cells are specialized cells that secrete mucus to protect the lining of the digestive tract, but they do not increase the surface area for absorption. C) Villi are finger-like projections in the small intestine that increase the surface area available for nutrient absorption. Each villus contains blood vessels and lacteals (lymphatic vessels) that help absorb nutrients from digested food. D) Paneth cells are specialized cells found in the small intestine that secrete antimicrobial substances, but they do not increase the surface area for absorption.

Correct Answer: D

Rationale: The speed of a wave in a given medium is determined by the properties of that medium, such as its density and elasticity. While amplitude, wavelength, and frequency are important characteristics of a wave, they do not directly impact its speed in a specific medium. Amplitude refers to the maximum displacement of particles in a wave, wavelength is the distance between two successive points in a wave that are in phase, and frequency is the number of complete oscillations a wave makes in a given time. However, these properties do not dictate the speed of a wave in a particular medium. Therefore, the correct answer is the medium's properties.

Correct Answer: A

Rationale: The primary function of the coronary arteries is to carry oxygenated blood to the heart muscle. Oxygenated blood is crucial for providing nutrients and oxygen to the heart muscle cells, enabling the heart to work efficiently. Without this oxygenated blood supply, the heart muscle may not receive the required nutrients and oxygen, potentially resulting in heart damage or dysfunction. Choices B, C, and D are incorrect as coronary arteries do not carry deoxygenated blood from the heart muscle, pump blood to the lungs for oxygenation, or regulate blood pressure in the systemic circulation. The coronary arteries specifically supply oxygenated blood to the heart muscle to support its function and vitality.