Assuming that all the heat energy turns into useful work, calculate how much coal per hour is enough

Assuming that all the heat energy turns into useful work, calculate how much coal per hour is enough for a 733 W machine.

Data: t (operating time of the machine used) = 1 hour (in SI t = 3600 s); N (machine power) = 733 W.

Constants: q (specific heat of combustion of coal) = 2.7 * 10 ^ 7 J / kg.

To calculate the sufficient mass of coal, we use the equality: q * m = A = N * t, whence m = N * t / q.

Let’s calculate: m = 733 * 3600 / (2.7 * 10 ^ 7) = 0.0977 kg (97.7 g).

Answer: 97.7 g of coal will be enough for the machine used.