According to the law of conservation of energy, when a lawnmower uses 750 J of chemical energy from gasoline, how much of this energy will be transformed into mechanical, sound, or heat energy?

Question

alekos · Answer

The internal combustion engine is extremely inefficient with most of the energy being converted to heat and sound.
From what I can remember a 4 stroke water cooled engine produces approximately 20% of mechanical or kinetic energy.

dqswag · Answer

yeah I got that but A.
	750 J
	
 
B.
	1500 J
	
 
C.
	325 J
	
 
D.
	162 J

dqswag · Answer

i dont get that

alekos · Answer

Well then I'd go for D which is 21.6% of 750J

ganeshie8 · Answer

Total energy cannot change, 
The chemical energy from gasoline used up just manifests as heat/mechanical or sound waves...

ganeshie8 · Answer

chemical energy used up =  sound + heat + mechanical

im inclining towards A

dqswag · Answer

OK um alekos how did u get your answer

dqswag · Answer

i see how genshine8 got hers or his

alekos · Answer

So is this a trick question? because kinetic energy (mechanical) would be around 20% and sound&heat would be 80% 
but the question does say " mechanical, sound and heat" which is 100% so A would strictly be correct

ipwnbunnies · Answer

I agree with Ganshie. I assuming the gasoline is the system, it does 750 Joules of work. That energy must be converted to something. It converts to 750 J done to the surroundings in any fashion.

dqswag · Answer

ohhh ok

ipwnbunnies · Answer

Meant to say gas uses 750 J of energy...

dqswag · Answer

so A

dqswag · Answer

thanks guys and or girls