Nursing Elites

1. Rusting of iron is an example of

• A. Endothermic reaction
• B. Exothermic reaction
• C. Single displacement reaction
• D. Photochemical reaction

Correct answer: A

Rationale: The rusting of iron is an endothermic reaction. This means that it absorbs heat from its surroundings to occur. Rusting involves the slow oxidation of iron in the presence of oxygen and water. As energy is absorbed during this process, it is classified as an endothermic reaction. Choice B, an exothermic reaction, releases heat instead of absorbing it, which is not the case in rusting. Choices C and D are unrelated to the process of rusting and do not involve the absorption of heat from the surroundings.

2. What are fingernails and toenails primarily made of?

• A. Collagen (Collagen is found in the dermis)
• B. Keratin
• C. Melanin (Melanin provides pigment, not structure)
• D. Sebum (Sebum is an oily substance)

Correct answer: B

Rationale: Fingernails and toenails are primarily made of a protein called keratin. Keratin is a tough, fibrous protein that provides structure and strength to nails, hair, and the outer layer of skin. Collagen, as mentioned, is found in the dermis and is not the primary component of nails. Melanin provides pigment to the skin and hair, not the structure of nails. Sebum is an oily substance produced by the skin's sebaceous glands and is not a structural component of nails.

3. What is the difference between a real image and a virtual image formed by a lens?

• A. Real images can be projected onto a screen, while virtual images cannot.
• B. Real images are always upright, while virtual images can be inverted.
• C. Real images are formed by converging lenses, while virtual images are formed by diverging lenses.
• D. All of the above are true.

Correct answer: A

Rationale: The correct answer is A. Real images can be projected onto a screen because they are formed by the actual convergence of light rays, while virtual images cannot be projected onto a screen as they appear to diverge from a point behind the lens. Real and virtual images do not have a consistent orientation (upright or inverted), so option B is incorrect. Real images are formed by both converging and diverging lenses depending on the specific scenario, so option C is not a definitive distinction. Option D is incorrect as not all the statements are true. Therefore, the only accurate general distinction between real and virtual images is that real images can be projected onto a screen, while virtual images cannot.

4. In nuclear physics, the term 'barn' is a unit commonly used to quantify:

• A. Energy
• B. Radioactivity
• C. Nuclear cross-section
• D. Half-life

Correct answer: C

Rationale: In nuclear physics, the term 'barn' is a unit used to quantify nuclear cross-section. Nuclear cross-section is a measure of the probability of a nuclear reaction occurring when an atomic nucleus interacts with a particle or another nucleus. The barn is a unit of area equal to 10^-28 square meters; it is commonly used to describe the cross-sectional area of atomic nuclei for nuclear reactions. Choice A, 'Energy,' is incorrect because a barn is not a unit for measuring energy; it is a unit of area. Choice B, 'Radioactivity,' is incorrect as radioactivity is typically measured in units like becquerels. Choice D, 'Half-life,' is also incorrect as half-life is a measure of the time it takes for half of a substance to decay, not related to the concept of a barn as a unit of nuclear cross-section.

5. An atom has 5 protons, 5 neutrons, and 6 electrons. What is the electric charge of this atom?

• A. Neutral
• B. Positive
• C. Negative
• D. Undetermined

Correct answer: C

Rationale: The correct answer is 'Negative.' An atom becomes negatively charged when it has more electrons than protons. In this case, the atom has 6 electrons and 5 protons, resulting in a net negative charge. Choice A 'Neutral' is incorrect because the atom is not balanced in terms of protons and electrons. Choice B 'Positive' is incorrect because having more electrons than protons results in a negative charge. Choice D 'Undetermined' is incorrect, as the charge can be determined based on the relative number of protons and electrons.

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