Blow air on a sheet of paper in kinetic energy Observation and conclusion
Answers
Answer: coanda effect
Explanation: the other answer suggests that bernulli's principle is what causes the sheet of paper to rise, however this is wrong.
Bernulli's principle doesn not state that a fast moving air necedsarelpy has a lower pressure then slow moving air. What it states is that to an acceleration correspondes a reduction in the pressure.
The air coming out of the mouth of the demonstrator has the exact same pressure as the air below the sheet of paper, atmospheric pressure. What is actually happening is that there is a higher pressure inside the mouth, and the air accelerates and is reduced back to air pressure when exiting the mouth.
The reason why the paper rises is because of the codana effect which says that the air blown above the sheet follows the curve and is redirected downward, thus producing a force upward that lifts the sheet of paper.
You can easily demonstrate this by blowing below the paper instead of above, if the fast moving air was really lower pressure then the sheet would bend even more downward , however this doesn't happen, and the sheet gets lifted