Nursing Elites

1. When a crane hoists a massive object at a constant velocity compared to lifting the same object gradually, the work done by the crane is:

• A. Less
• B. More
• C. Identical
• D. Dependent on the object's mass

Correct answer: C

Rationale: The work done by the crane is identical in both scenarios. Work is defined as the force applied over a distance. Since the force needed to lift the object is equal to its weight and the displacement is the same, the work done is identical, whether the object is lifted gradually or at a constant velocity. Choice A is incorrect because the work done is the same in both cases. Choice B is incorrect as well since the work done does not increase. Choice D is incorrect as the mass of the object does not affect the work done by the crane in this scenario.

2. Why are boats more buoyant in salt water than in fresh water?

• A. Salt decreases the mass of the boats.
• B. Salt increases the volume of the water.
• C. Salt affects the density of the boats.
• D. Salt increases the density of the water.

Correct answer: D

Rationale: Salt increases the density of water, making saltwater more buoyant than freshwater. The higher density of saltwater provides more lift to a boat, enabling it to float more easily compared to in freshwater. Choice A is incorrect because salt does not affect the mass of the boats. Choice B is incorrect as salt does not increase the volume of water. Choice C is incorrect since salt affects the density of water, not the boats themselves. Therefore, the correct answer is that salt increases the density of the water, resulting in boats being more buoyant in salt water than in fresh water.

3. Cavitation is a phenomenon observed in fluids when the pressure falls below its:

• A. Boiling point
• B. Density
• C. Freezing point
• D. Vapor pressure

Correct answer: D

Rationale: Cavitation is a phenomenon where vapor bubbles form in a fluid due to pressure dropping below the vapor pressure of the liquid. When this occurs, the bubbles collapse, creating intense shock waves. The pressure falling below the vapor pressure is what triggers cavitation, not the boiling point, density, or freezing point of the fluid. Therefore, the correct answer is 'Vapor pressure,' as it directly relates to the pressure threshold required for cavitation to happen.

4. Longitudinal waves have vibrations that move ___________.

• A. at right angles to the direction of the vibrations
• B. in the direction opposite to that of the wave
• C. in the same direction as the wave
• D. in waves and troughs

Correct answer: C

Rationale: In longitudinal waves, the vibrations of particles occur in the same direction as the wave propagates. This means the particles move back and forth in the direction of the wave, creating compressions and rarefactions along the wave. Therefore, the correct choice is C, in the same direction as the wave. Choice A is incorrect because transverse waves, not longitudinal waves, have vibrations at right angles to the direction of wave propagation. Choice B is incorrect as it describes the motion in transverse waves. Choice D is incorrect as it is an inaccurate representation of how longitudinal waves propagate.

5. An object with a charge of 4 μC is placed 50 cm from another object with a charge twice as great. What is the magnitude of the resulting repulsive force?

• A. 0.1152 N
• B. 1.152 N
• C. 10^−3 N
• D. 2.5 × 10^−3 N

Correct answer: D

Rationale: The force between two charges is calculated using Coulomb's Law, which states that the force is proportional to the product of the two charges and inversely proportional to the square of the distance between them. Given that one charge is twice as great as the other and the distance between them is 50 cm, we can calculate the repulsive force. The magnitude of the resulting repulsive force is 2.5 × 10^−3 N. Choice A is incorrect as it does not match the calculated value. Choice B is incorrect as it is significantly higher than the correct answer. Choice C is incorrect as it represents 10^−3 N, which is lower than the calculated value.

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