Answer:
You're strong.
Explanation:
I've been thinking of this for quite a while, and I realized that your body has a certain limit to how much pain it can take. So, punching yourself extremely hard will cause pain, because that's your body's reaction to immense pressure being put on it. But, the fact that you punched yourself so hard that it hurts, shows that you are capable of applying so much pressure; therefore, you are strong.
The thermal efficiency of an engine is

where
W is the work done by the engine
Q is the heat absorbed by the engine to do the work
In this problem, the work done by the engine is W=200 J, while the heat exhausted is Q=600 J, so the efficiency of the machine is
The total amount of energy remains constant in an isolated system. It implies that energy can neither be created nor destroyed, but can be change from one form to another.
1.) The object's Velocity
Faster it goes, more kinetic energy it has