Formula for working out power produced by petrol being burnt in an engine

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
Sign up Log in
2 replies · 4K views
clifftifer
Messages
1
Reaction score
0
Iam not looking for the answer, I would just like to pointed in the right direction with the formula which would help me work this out. Its been a number of years since I have had to do this. (AN EXTREMELY MATURE STUDENT) Thank you

If the fuel consumption of a car, traveling at a steady 60 mph, is 20 mpg what is the power produced by the petrol being burnt in the engine? [Assume that the density of petrol is 0.84 kg/l and the heat of combustion of petrol is 47 302 kJ/kg]
 
Physics news on Phys.org

Discussion

Hi clifftifer! Welcome to PF :smile:

Power is the rate of energy used up or work done in unit time. Can you find this from the given information??
 
clifftifer said:
Iam not looking for the answer...
And proper PF members wouldn't give it to you, even if you asked politely.

Infinitum said:
Hi clifftifer! Welcome to PF :smile:

Power is the rate of energy used up or work done in unit time. Can you find this from the given information??

I had to throw in a few of other bits of information before I could come up with the answer:

1 watt = 1 joule/second
3.785 liters = 1 gallon
3600 seconds = 1 hour
745.7 watts = 1 hp​

to yield the answer in hp.

To start, my equation looked like:
x watts = 47,302,000 joules/kg * .......​

I ended up with joules/second, and then converted to hp.

Simple plug and chug, as we used to call it. hmmm... Do people still use that phrase; "plug and chug"?