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Question:

HELP ME OUT?!?!?!??????????

Aluminum has a specific heat of 0.902 J/g x oCTwo pieces of aluminum, with masses of 10 kg, cool from 400 oC to 100oCOne mass is round; the other is a cubeAll BUT one statement is true regarding the energy transformationThat is A) both masses lose the same amount of heat energy B) the masses cool in approximately the same amount of time C) the heat energy lost is directly related to the shape of the object D) the kinetic energies of the masses decrease during the cooling process.

Answer:

I suggest that the answer is A) both masses lose the same amount of heat energyThis is because the relationship governing energy and temperature difference is Emc(dT), so for a fixed drop in temperature, there is only a fixed drop in energy for the same material irrespective of the shapeReasons why B), C), and D) are not correct: B) the masses cool in approximately the same amount of time : This is not possible as the mass with the larger surface area is likely to lose heat at a higher rateTHIS DOESN'T MEAN THAT IT LOSES MORE HEAT, just that it loses heat fasterThe final energies will be the sameC) the heat energy lost is directly related to the shape of the objectNot necessarily, the rate of energy loss as above depends on the surface area of the mass, while the total heat energy loss may depend on the temperature of the surrounding rather than the shape of the objectD) the kinetic energies of the masses decrease during the cooling processThis statement is correct but misleadingThe masses are not thrown or anything for them to posses any kinetic energy, however if they were referring to internal kinetic energy(which determines the internal energy of the mass and is related to temperature) then this could have been true as the particles in the mass reduce their vibrations when cooling down and therefore internal kinetic energy decreasesHowever, the statement given gives no indication of whether it is internal KE, and hence we can assume that it is not the case.

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