Question at position 3 Sam scenario as above: You are lifting an 85 pound weight up a distance of 1.5 meters in 2 seconds. What is the work? 378 J567 J834 J1251 J单项选择题
A
378 J
B
567 J
C
834 J
D
1251 J

Question

Question at position 3  Sam scenario as above: You are lifting an 85 pound weight up a distance of 1.5 meters in 2 seconds. What is the work? 378 J567 J834 J1251 J

BlackTom AI · Accepted Answer

Work equals force times displacement, so W = F · d. Here the 85-pound figure is a weight (force). Convert pounds to newtons (1 lb ≈ 4.44822 N) and multiply by the vertical displacement. Time does not affect the work (it would affect power).

Step-by-step:
1. Convert force: F = 85 lb × 4.44822 N/lb
   F = 85 × 4.44822 = 378.0987 N (intermediate value).
2. Multiply by displacement: W = F × d = 378.0987 N × 1.5 m
   W = 567.14805 J.
3. Round to sensible precision (given answer choices are whole joules): W ≈ 567 J.

Why this is correct:
- Work is the product of the force applied in the direction of motion and the distance moved. Using the standard conversion from pounds-force to newtons yields 378.10 N; multiplying by 1.5 m gives 567.15 J, which matches 567 J when rounded.

Why the other choices are incorrect:
- 378 J: This is approximately the force in newtons (378 N) but not the work; it would be the work only if the object were moved 1.0 m, not 1.5 m.
- 834 J: This is larger than the correct product; it does not result from the correct conversion and multiplication (no standard intermediate step gives 834 J for these inputs).
- 1251 J: This is roughly double the correct value and might result from a mistaken doubling (for example, multiplying by an incorrect distance or using an extra factor), so it is not correct.

Final confirmation: The calculated work is about 567 J, which matches the provided correct answer: 567 J.

Question at position 3 Sam scenario as above: You are lifting an 85 pound weight up a distance of 1.5 meters in 2 seconds. What is the work? 378 J567 J834 J1251 J单项选择题

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