HESI A2
HESI A2 Physics
1. A 10-kg object moving at 5 m/s has an impulse acted on it causing the velocity to change to 15 m/s. What was the impulse that was applied to the object?
- A. 10 kgâ‹…m/s
- B. 15 kgâ‹…m/s
- C. 20 kgâ‹…m/s
- D. 100 kgâ‹…m/s
Correct answer: D
Rationale: Impulse is the change in momentum of an object. The initial momentum is calculated as 10 kg × 5 m/s = 50 kg⋅m/s, and the final momentum is 10 kg × 15 m/s = 150 kg⋅m/s. The change in momentum (impulse) is 150 kg⋅m/s - 50 kg⋅m/s = 100 kg⋅m/s. Therefore, the impulse applied to the object is 100 kg⋅m/s. Choices A, B, and C are incorrect because they do not reflect the correct calculation of the impulse based on the change in momentum of the object.
2. A key parameter in fluid selection is specific gravity (SG). For a submerged object in a reference fluid (often water), SG = Ï_object / Ï_reference. An object with SG > 1 will:
- A. Experience a net buoyant force acting upwards
- B. Experience a net buoyant force acting downwards
- C. Remain neutrally buoyant
- D. Require knowledge of the object's volume for buoyancy determination
Correct answer: A
Rationale: When the specific gravity (SG) of an object is greater than 1, it indicates that the object is denser than the reference fluid, which is often water. According to Archimedes' principle, an object with SG > 1 will experience a net buoyant force acting upwards when submerged in the fluid. This is because the buoyant force is greater than the weight of the object, causing it to float. Therefore, the correct answer is A: 'Experience a net buoyant force acting upwards.' Objects with SG < 1 would sink as they are less dense than the fluid, while objects with SG = 1 would be neutrally buoyant, neither sinking nor floating.
3. In a parallel circuit, the ___________ through each component is the same.
- A. current
- B. voltage
- C. resistance
- D. wattage
Correct answer: A
Rationale: In a parallel circuit, the current through each component is the same. This is because the components in a parallel circuit are connected across the same voltage source, so they all experience the same voltage across their terminals. The total current entering the parallel circuit is then split up among the various components, but the current through each component remains the same as the total current. Choices B, C, and D are incorrect. In a parallel circuit, voltage across each component may vary, resistance may differ, and wattage is related to power, not the equality of current through each component.
4. 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.
5. A wave moves through its medium at 20 m/s with a wavelength of 4 m. What is the frequency of the wave?
- A. 5 s−1
- B. 16 s−1
- C. 24 s−1
- D. 80 s−1
Correct answer: C
Rationale: The formula to calculate the frequency of a wave is given by:
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