1 horsepower is equal to 746 W, so the power of the engine is
[tex]P=47.4 hp \cdot 746 \frac{W}{hp}=35360 W [/tex]
The power is also defined as the energy E per unit of time t:
[tex]P= \frac{E}{t} [/tex]
Where the energy corresponds to the work done by the engine, which is [tex]E=6.82 \cdot 10^5 J[/tex]. Re-arranging the formula, we can calculate the time t needed to do this amount of work:
[tex]t = \frac{E}{P}= \frac{6.82 \cdot 10^5 J}{35360 W}=19.3 s [/tex]
