【单选题】
A food shipper pushes a wood crate (板条箱) of cabbage heads (包心菜) ( total mass m = 14kg) across a concrete floor with constant horizontal force F of magnitude 40N. In a straight-line displacement of magnitude d = 0.50m, the speed of the crate decreases from v 0 = 0.60m/s to v = 0.20m/s. How much is the increase of thermal energy Δ E th in J between the crate and floor?
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参考解析:
举一反三
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