ANSWER: Destructive Interference
-This is the exact definition of the question you have provided, look this term up if you do not believe lol.
Hope this Helps!
Answer:
You are exactly right. The molecules in hot air are moving faster than the molecules in cold air. Because of this, the molecules in hot air tend to be further apart on average, giving hot air a lower density. That means, for the same volume of air, hot air has fewer molecules and so it weighs less
That would be a conduction.
Friction but i may be wrong
Efficiency of a simple machine is the ratio of mechanical advantage and speed ratio.
If mechanical advantage = speed ratio then efficiency = 1
Which is impossible for a practical machine due to presence of frictional force which wastes some energy and thus lowers the output
