Question

Help?

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?

A. 1500 J

B. 162 J

C. 750 J

D. 325 J

Answer 1

You can exclude 2 choices already. You cannot get more than what you put in, right?

Answer 2

It would help if you look at the law of conservation of energy itself.

Answer 3

My gosh, I'm so slow today. XD Mkay... I'll look at it.

Answer 4

Well I made a mistake too. We can exclude only 1 immediately using logic.

Answer 5

So, that would mean, you'd have to eliminate, A. If your only putting in 750, how would you get 1500?

Answer 6

Yup. Another way to see it is if you eat 2 donuts, you cannot feel as full as eating 5 donuts, nor have the energy of 5 donuts.

"One way to state this principle is "Energy can neither be created nor destroyed". Another approach is to say that the total energy of an isolated system remains constant."
http://hyperphysics.phy-astr.gsu.edu/hbase/conser.html

Do you understand what the law is?

Answer 7

I think so... What I'm thinking is now, if you have 750 J, would you divide it 3 ways, into mechanical, sound, and heat energy?

Answer 8

Wait, if you divide it into 3 ways, that would give you 250, and that's not an answer. .-.

Answer 9

Wait a minute... is the answer, C., 750? If you put in 750, you'd get 750 out? Have I been complicating myself? XD

Answer 10

Yea I was confused about how the question was worded too but paraphrased, it's asking the total heat, sound, and mechanical energy you get. Meaning, what's the most you have from either or any combinations of those energies. And yes, you will get 750 J as what you put in.

Answer 11

Wow. I can't believe it was that simple. XD Thanks for your help @wolfe8! If you hadn't helped me, I'd still be thinking to divide the 750 J into thirds. XD

Answer 12

Yup no problem. I did that too :P This one was more of understanding the question.