Final answer:
The statement regarding the calculation of energy efficiency by multiplying service and energy used is false; efficiency is the ratio of useful energy output to energy input.
Step-by-step explanation:
Energy efficiency is not calculated by multiplying the amount of service provided by the amount of energy used. This statement is false. Instead, energy efficiency is calculated as the ratio or proportion of useful energy (work) output to the total input of energy (the energy consumed to perform a task). In other words, an engine's efficiency equals the proportion of useful energy (work) to the input energy.
The formula for calculating efficiency is (useful output energy / input energy) × 100 percent. Moreover, it's crucial to understand that the efficiency of a simple machine is always less than 100 percent because of losses, such as those due to friction, that convert some input work to heat energy.