Question

While helping a friend shift furniture you do 2.2 MJ of mechanical work at and efficiency of 11% (η = 0.11).
How much food energy would you need to ingest in order to prevent weight loss? (to 2 s.f and in MJ)

Answer 1

Solution:

$A=2.2 MJ;$

$\eta=0.11;$

$Q-?;$

The efficiency is calculated by the formula:

$\eta=\dfrac{A}{Q};\implies Q=\dfrac{A}{\eta};$

$Q=\dfrac{2.2MJ}{0.11}=20MJ;$

Answer: $Q=20MJ.$