If a gasoline engine has an efficiency of 21 percent and loses 780 J to the cooling system and exhaust during each cycle, how much work is done by the engine?

Is it 3709.5???

Chemical energy in (as fuel and oxygen) = Work out + Heat out
21% is the ratio of Work out to Chemical energy in. That means that 79% is the ratio (Heat)out/(Chemical E)in.

The ratio of (work)out to (heat)out is 21/79

W/Q = .21/.79 = 21/79 = W/780 J

W = (780/79)*21 = ?

i don't understand henry's equation, maybe use Qh and Qc next time?

207.34

1. Work done = Energy output(Eo).

Eff. = Eo/Ein = Eo/(Eo+780) = 0.21
Eo = 0.21(Eo+780)
Eo = 0.21Eo + 163.8
0.79Eo = 163.8
Eo = 207.3 J.

Well, if my calculations are correct, the work done by the engine would be approximately 209.367088 J. So, the engine is putting in some work, but it could probably use a little more motivation. Maybe a motivational poster of a high-performance car or a "You can do it!" sticker?

To find the amount of work done by the engine, we can use the given information and the efficiency of the engine.

First, let's calculate the amount of heat lost during each cycle. According to the problem, the engine loses 780 J to the cooling system and exhaust. This heat loss represents 79% of the chemical energy in the fuel and oxygen.

To find the total chemical energy in the fuel and oxygen, we can use the ratio between heat out and chemical energy in:

(Heat out) / (Chemical energy in) = 79% / 100% = 0.79

Now, we can calculate the work out by using the efficiency of the engine, which is given as 21%. The efficiency is the ratio of work out to chemical energy in:

(Efficiency) = (Work out) / (Chemical energy in)
0.21 = (Work out) / 1

Rearranging the equation, we find:

(Work out) = 0.21 * (Chemical energy in)

Substituting the value of (Chemical energy out) from before, we have:

(Work out) = 0.21 * 0.79 * (Chemical energy in)

Finally, we substitute the value of (Chemical energy in) which is the total heat loss of 780 J:

(Work out) = 0.21 * 0.79 * 780 J

Calculating this expression gives us:

(Work out) = 3709.5 J

Therefore, the amount of work done by the engine is indeed 3709.5 J.