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 ([tex]\dot W[/tex]), measured in watts, is at constant rate. Then, the work needed by the horse ([tex]W[/tex]), measured in joules, is equal to that power multiplied by time ([tex]\Delta t[/tex]), measured in seconds. That is:
[tex]W = \dot W\cdot \Delta t[/tex] (1)
If we know that [tex]\dot W = 750\,W[/tex] and [tex]\Delta t = 3600\,s[/tex], then the work needed for the horse is:
[tex]W = (750\,W)\cdot (3600\,s)[/tex]
[tex]W = 2.7\times 10^{6}\,J[/tex]
[tex]W = 2.7\,MJ[/tex]
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.
