He is pulling 400 feet over level ground by exerting a constant 25-pound force on the bar that makes an angle of 30° with the ground. How much work is Thomas doing to pull the wagon?

Work is the force in the direction of motion multiplied by the distance. Since the wagon moves horizontally and the 25-pound force is angled 30° above the ground, the horizontal force is 25 cos(30°) ≈ 21.65 pounds. Thus, the work is 21.65 × 400 ≈ 8,660 foot-pounds, so the answer is B, 8,660 foot-pounds.

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