A heat engine does 650 J of work and dumps 1270 J of heat to its cold reservoir. What is its efficiency?

To calculate the efficiency of a heat engine, you need to use the formula:

Efficiency = (Work output / Heat input)

Given that the heat engine does 650 J of work (work output) and dumps 1270 J of heat to its cold reservoir (heat input), you can substitute these values into the formula to find the efficiency.

Efficiency = (650 J / 1270 J)

Now let's calculate the efficiency:

Efficiency = (650 / 1270) ≈ 0.511 or 51.1%

Therefore, the efficiency of the heat engine is approximately 51.1%.