HESI A2
HESI A2 Physics
1. If a force of 12 kg stretches a spring by 3 cm, how far will the spring stretch when a force of 30 kg is applied?
- A. 6 cm
- B. 7.5 cm
- C. 9 cm
- D. 10.5 cm
Correct answer: B
Rationale: The extension of a spring is directly proportional to the force applied. In this case, the force increases from 12 kg to 30 kg, which is a 2.5 times increase. Therefore, the extension of the spring will also increase by 2.5 times. Given that the spring stretches 3 cm with a force of 12 kg, multiplying 3 cm by 2.5 gives us the extension of the spring when a force of 30 kg is applied, which equals 7.5 cm. Therefore, the correct answer is 7.5 cm. Choice A, 6 cm, is incorrect because it does not account for the proportional increase in force. Choice C, 9 cm, and Choice D, 10.5 cm, are incorrect as they overestimate the extension of the spring by not considering the direct proportionality between force and extension.
2. A 0-kg block on a table is given a push so that it slides along the table. If the block is accelerated at 6 m/s2, what was the force applied to the block?
- A. 0 N
- B. 3 N
- C. 6 N
- D. The answer cannot be determined from the information given.
Correct answer: A
Rationale: According to Newton's second law of motion, F=ma. Since the block has a mass of 0 kg, the force applied must be 0 N, as no force is needed to move an object with zero mass.
3. Why does potential energy increase as particles approach each other?
- A. Attractive forces increase.
- B. Attractive forces decrease.
- C. Repulsive forces increase.
- D. Repulsive forces decrease.
Correct answer: C
Rationale: The correct answer is C: Repulsive forces increase. As particles approach each other, the distance between them decreases, causing the repulsive forces between the particles to increase. This increase in repulsive forces leads to an increase in potential energy as the particles resist being pushed closer together. Choices A and B are incorrect because attractive forces do not increase or decrease in this scenario. Choice D is incorrect because repulsive forces actually increase as particles get closer, leading to a rise in potential energy.
4. Why doesn’t a raindrop accelerate as it approaches the ground?
- A. Gravity pulls it down at a constant rate.
- B. Air resistance counteracts the gravitational force.
- C. Its mass decreases, decreasing its speed.
- D. Objects in motion decelerate over distance.
Correct answer: B
Rationale: The correct answer is B. As a raindrop falls, it experiences air resistance which counteracts the gravitational force pulling it down. This balancing of forces prevents the raindrop from accelerating further as it approaches the ground. Choice A is incorrect because while gravity is pulling the raindrop down, air resistance opposes this force. Choice C is incorrect as the mass of the raindrop remains constant during its fall. Choice D is incorrect because objects in motion may decelerate due to various factors, but in this case, the focus is on why the raindrop doesn't accelerate.
5. What is the mathematical expression for work (W)?
- A. W = F / d
- B. W = F x d
- C. W = d / F
- D. W = F^2 x d
Correct answer: B
Rationale: The correct formula for work (W) is given by the equation W = F x d, where F represents force and d represents the displacement in the direction of the force. Work is calculated by multiplying the force applied by the distance over which the force is applied. Choice A (W = F / d) is incorrect as work is not calculated by dividing force by distance. Choice C (W = d / F) is incorrect because work is not calculated by dividing distance by force. Choice D (W = F^2 x d) is incorrect as work is not calculated by squaring the force and then multiplying by distance.
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