A machine gear consists of 0.14 kg of iron and 0.19 kg of copper.How much total heat is generated in the part if its temperature increases by 35.0 C°? (Specific heats of iron and copper are 450 and 390 J/kg⋅°C,respectively. )
A)4.5E+3 J
B)4.8E+3 J
C)5.2E+3 J
D)2.2E+3 J
E)2.6E+3 J

Question

Quizplus · Accepted Answer

First, we need to calculate the heat generated separately for iron and copper, and then add them to get the total heat generated.

Heat generated by iron = mass x specific heat x temperature change 
= 0.14 kg x 450 J/kg⋅°C x 35.0 C° 
= 2205 J

Heat generated by copper = mass x specific heat x temperature change 
= 0.19 kg x 390 J/kg⋅°C x 35.0 C° 
= 2565 J

Total heat generated = Heat generated by iron + Heat generated by copper 
= 2205 J + 2565 J 
= 4770 J

Rounding off to 2 significant figures, we get 4.8E+3 J as the answer. Therefore, the best choice is B.

A Machine Gear Consists of 0