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Two objects attract each other with a gravitational force of 12 units. If you double the distance between the objects, what is the new force of attraction between the two?
- A. 3 units
- B. 6 units
- C. 24 units
- D. 48 units
Correct Answer: A
Rationale: The gravitational force between two objects is inversely proportional to the square of the distance between them. If the distance is doubled, the force will be reduced to 1/4 of the original force. Therefore, the new force of attraction between the two objects will be 12 units / 4 = 3 units. Choice A is correct because doubling the distance reduces the force to 1/4 of the original value. Choices B, C, and D are incorrect as they do not consider the inverse square relationship between distance and gravitational force.
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What is the main difference between a reversible and irreversible process in thermodynamics?
- A. Reversible processes involve heat transfer, while irreversible processes do not.
- B. Reversible processes occur instantaneously, while irreversible processes take time.
- C. Reversible processes can be run in both directions with the same outcome, while irreversible processes cannot.
- D. Reversible processes violate the first law of thermodynamics.
Correct Answer: C
Rationale: A reversible process is an idealized process that can be reversed without leaving any change in either the system or the surroundings. In contrast, irreversible processes cannot be reversed and often involve entropy production or dissipation. Choice A is incorrect because both reversible and irreversible processes can involve heat transfer. Choice B is incorrect as the speed of a process does not determine its reversibility. Choice D is incorrect because reversible processes do not violate the first law of thermodynamics; they comply with it by maintaining a balance between energy inputs and outputs. Therefore, the correct answer is C, as it accurately captures the main difference between reversible and irreversible processes in thermodynamics.
A constant force is exerted on a stationary object. In this scenario, work is:
- A. Performed
- B. Not performed
- C. Partially performed
- D. Inconclusive without further information
Correct Answer: B
Rationale: Work is only done when a force causes displacement. Since the object is stationary, no displacement occurs, and therefore, no work is performed. Choice A is incorrect because work requires both force and displacement. Choice C is incorrect as there is no partial work - work is either done or not done. Choice D is incorrect as the scenario provided is clear - the object is stationary, so no work is being performed.
A 3-volt flashlight uses a bulb with 60-ohm resistance. What current flows through the flashlight?
- A. o.05 amp
- B. o.5 amp
- C. 1.8 amp
- D. 18 amp
Correct Answer: A
Rationale: : Using Ohm's Law, I = V / R:
I = 3 / 60 = 0.05 amp.
So, the correct current is 0.05 amp.
An object moves 100 m in 10 s. What is the velocity of the object over this time?
- A. 10 m/s
- B. 90 m/s
- C. 110 m/s
- D. 1,000 m/s
Correct Answer: A
Rationale: Velocity is calculated as the displacement divided by the time taken to cover that displacement. In this case, the object moves 100 meters in 10 seconds. Therefore, the velocity is 100 m / 10 s = 10 m/s. Choice B, 90 m/s, is incorrect as it doesn't match the calculated velocity. Choice C, 110 m/s, is incorrect as it is higher than the calculated velocity. Choice D, 1,000 m/s, is incorrect as it is significantly higher than the calculated velocity.
How do a scalar quantity and a vector quantity differ?
- A. A scalar quantity has both magnitude and direction, and a vector does not.
- B. A scalar quantity has direction only, and a vector has only magnitude.
- C. A vector has both magnitude and direction, and a scalar quantity has only magnitude.
- D. A vector has only direction, and a scalar quantity has only magnitude.
Correct Answer: C
Rationale: The correct answer is C. The main difference between a scalar quantity and a vector quantity lies in the presence of direction. A vector quantity has both magnitude and direction, while a scalar quantity has magnitude only, without any specified direction. Examples of scalar quantities include distance, speed, temperature, and energy, whereas examples of vector quantities include displacement, velocity, force, and acceleration. Choices A, B, and D are incorrect because they incorrectly describe the characteristics of scalar and vector quantities.