12.鋁與銅的比熱值與原子量分別為 0.215 cal/g℃、27；0.0923 cal/g℃、63.5；兩者轉換為莫耳比熱，使用單位為 J/mol℃。下列何者較正確？ (A) 鋁的莫耳比熱約為 48.3 (B) 銅的莫耳比熱約為 5.86 (C) 因銅密度大，故莫耳比熱質較大 (D) 以上皆正確

2. A 4.00-kg box sits atop a 10.0-kg box on a horizontal table. The coefficient of kinetic friction between the two boxes and between the lower box and the table is 0.600, while the coefficient of static friction between these same surfaces is 0.800. A horizontal pull to the right is exerted on the lower box, as shown in the figure, and the boxes move together. What is the friction force on the UPPER box? (A) 19.3 N to the right (B) 19.3 N to the left (C) 23.5 N to the right(D) 31.4 N to the right (E) 31.4 N to the left

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