When gasoline is burned, it gives off 46,000 J/gram of heat energy. If an automobile uses 13.0 kg of gasoline per hour with an efficiency of 21%, what is the average horsepower output of the engine

the  average horsepower output of the engine is 46.76 hp

Explanation:

The computation of the  average horsepower output of the engine is shown below

The output of the engine is

= (Energy content of gasoline) × (usage of the fuel ) ×  (Fuel efficiency)

As we know that

1 hp = 746 W

where,

Energy content of gasoline = 46000 J / g = 4.6  × 107 J/kg

Usage of the fuel = 13 kg / h = 13 ÷ 3600 kg/s

Fuel efficiency = 21% = 0.21

Therefore, the output of the engine is

= 4.6 ×  107 × (13 ÷ 3600) × 0.21 × (1 ÷ 746) h.p.

= 46.76 h.p.

hence, the  average horsepower output of the engine is 46.76 hp

3.2x10^7

see earlier