There is a little island off the shore of Brazil where the weather is extremely consistent. From 1911 to 1990, the lowest temperature on the island was 18°C (64°F) and the highest temperature was 32°C (90°F). It is known that the liquid in a standard can of soft drink absorbs 20.8 kJ of energy when its temperature increases from 18.0°C to 32.0°C. If the soft drink has a mass of 0.355 kg, what is its specific heat capacity?

answer: the potential energy decreases from 379 j to 243 j

explanation:

for the law of conservation of energy, the total energy in a system must be conserved. the total energy of the system is given by the sum of kinetic (k) and potential (u) energy:

e = k + u

the total energy is e=675 j, and this does not change.

initially, the kinetic energy is k=296 j, so the potential energy is

at the end, the kinetic energy is k=432 j, so the potential energy is

so, we see that the potential energy has decreased from 379 j to 243 j.