To solve this we are going to use a conversion factor. We know that 1 BTU per hour is approximately 778 foot-pounds of energy per hour, so our conversion factor will be: [tex] \frac{778foot-pound}{1BTU} [/tex].
Now we just need to multiply 4000 BTU by our conversion factor:
[tex]4000BTU*\frac{778foot-pound}{1BTU}=3112000foot-pound[/tex]
We can conclude that the furnace released 3,112,000 foot pounds of energy in one hour.