Question

An automobile engine delivers 47.4 hp. how much time will it take for the engine to do 6.82 × 105 j of work? one horsepower is equal to 746 watts. answer in units of s.

Answer 1

1 horsepower is equal to 746 W, so the power of the engine is

`P=47.4 hp \cdot 746 (W)/(hp)=35360 W`
The power is also defined as the energy E per unit of time t:

`P= (E)/(t)`
Where the energy corresponds to the work done by the engine, which is
`E=6.82 \cdot 10^5 J`. Re-arranging the formula, we can calculate the time t needed to do this amount of work:

`t = (E)/(P)= (6.82 \cdot 10^5 J)/(35360 W)=19.3 s`