Nursing Elites

1. What determines the magnitude of the frictional force acting on a book sliding across a table?

• A. Only the mass of the book
• B. Only the normal force from the table
• C. Both the mass of the book and the normal force from the table
• D. Neither the mass of the book nor the normal force from the table

Correct answer: C

Rationale: The magnitude of the frictional force acting on the book sliding across a table is determined by both the mass of the book and the normal force from the table. Frictional force is proportional to the normal force (which is influenced by the weight of the book, i.e., its mass) and is affected by the surfaces in contact and other friction-related factors. Therefore, both the mass of the book and the normal force from the table are essential in determining the frictional force experienced by the book during its sliding motion. Choices A, B, and D are incorrect because friction is a result of the interaction between the surfaces and is influenced by both the mass of the object and the normal force acting on it.

2. Which of the following enzymes unwinds the double-stranded DNA during replication?

• A. Helicase
• B. Ligase
• C. Nuclease
• D. Polymerase

Correct answer: A

Rationale: Helicase is the enzyme responsible for unwinding the double-stranded DNA during replication by breaking the hydrogen bonds between the base pairs. This process creates the replication fork where DNA polymerase can then synthesize new DNA strands. Ligase functions to join Okazaki fragments on the lagging strand, not unwind DNA. Nuclease is involved in DNA repair by removing damaged DNA segments. Polymerase is responsible for synthesizing new DNA strands based on the existing template strands, not for unwinding the DNA.

3. Which organ system is most responsible for maintaining control of body temperature?

• A. The skeletal system.
• B. The circulatory system.
• C. The immune system.
• D. The muscular system.

Correct answer: B

Rationale: The circulatory system is the correct answer as it plays a crucial role in maintaining control of body temperature through a process called thermoregulation. Blood vessels near the skin surface dilate to dissipate heat when the body is too warm and constrict to reduce heat loss when it's too cold. Additionally, the circulatory system helps distribute heat produced from metabolic processes throughout the body to keep a stable internal temperature. The skeletal system provides structural support, the immune system defends against pathogens, and the muscular system is responsible for movement, but they are not primarily involved in regulating body temperature.

4. Which structure in the lungs is the site of gas exchange?

• A. Trachea
• B. Alveoli
• C. Bronchioles
• D. Diaphragm

Correct answer: B

Rationale: The correct answer is B: Alveoli. Alveoli are tiny air sacs in the lungs where gas exchange occurs. Oxygen from inhaled air diffuses into the bloodstream, while carbon dioxide from the blood is released into the alveoli to be exhaled. The trachea (Choice A) is the windpipe that carries air to and from the lungs, but it is not involved in gas exchange. Bronchioles (Choice C) are small air passages within the lungs that branch off from the bronchi, leading air to the alveoli but not directly involved in gas exchange. The diaphragm (Choice D) is a muscle below the lungs that helps in breathing by expanding and contracting the chest cavity, but it is not the site of gas exchange.

5. Two identical balls, one made of clay and the other made of steel, are dropped from the same height. Which ball reaches the ground first, neglecting air resistance?

• A. The clay ball due to its lower density
• B. The steel ball due to its higher density
• C. Both balls reach the ground simultaneously
• D. It depends on the initial velocities of the balls

Correct answer: C

Rationale: In the absence of air resistance, both balls will experience the same acceleration due to gravity (9.8 m/s^2) regardless of their densities or materials. This means that both balls will reach the ground at the same time, assuming they are dropped from the same height simultaneously. The differences in density or material composition do not affect the rate at which objects fall in a vacuum. Therefore, both the clay and steel balls, being identical in shape and starting position, will have the same free-fall acceleration and will hit the ground simultaneously. Choices A and B are incorrect because the density of the materials does not impact the time it takes for objects to fall under gravity alone. Choice D is incorrect as the initial velocities do not play a role in the time taken to fall in a vacuum, where only the acceleration due to gravity affects the motion.

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