Question

A horse is working steadily, providing 750 W of output power. How much food energy does the horse need to work for 1 hour, to the nearest MJ

Answer 1

Answer:

Under assumption that all food energy that needs the horse is transformed into work, then the horse needs approximately 3 megajoules of food energy to work for 1 hour.

Explanation:

Since horse is working steadily, the power experimented by the horse ($\dot W$), measured in watts, is at constant rate. Then, the work needed by the horse ($W$), measured in joules, is equal to that power multiplied by time ($\Delta t$), measured in seconds. That is:

$W = \dot W\cdot \Delta t$ (1)

If we know that $\dot W = 750\,W$ and $\Delta t = 3600\,s$, then the work needed for the horse is:

$W = (750\,W)\cdot (3600\,s)$

$W = 2.7\times 10^{6}\,J$

$W = 2.7\,MJ$

Under assumption that all food energy that needs the horse is transformed into work, then the horse needs approximately 3 megajoules of food energy to work for 1 hour.