Question

In football sport a banana kick is an off centre kick that makes the ball curve or suddenly changes direction mid air. The player achieves this by imparting revolution on the ball while kicking. The physical principle which best describes the banana kick is:
A) Hooke’s Law
B) Bernoulli’s Law
C) Torricelli's Law
D) Newton Law of Motion

Answer 1

Hint:When the football is spinned by kicking in one specific direction, then it results into a banana kick. This causes a difference of velocity on different portions of the ball, which produces a force. This force is responsible for moving the ball sideways in one specific direction. First of all the ball is made to move in one direction sideways, then the principle acting on it is to be determined.

Step-by-Step Explanation:
Step I: When the ball is struck slightly off centre, it spins in a horizontal direction. This makes the ball curve in sideways curving direction.
Step II: Now here ‘Bernoulli’s Principle’ is seen. As per this principle, if the pressure exerted by air decreases, then its velocity will increase. This shows that pressure is inversely proportional to velocity here.
Step III: When the ball is kicked and made to move forward, then air flows from all directions on its sides. But on the other hand, when the ball is spinning, then the side of the ball which is moving in the direction of airflow, will travel faster and easier.
But if the ball moves in a direction opposite to the air flow, then the amount of pressure on that side of the ball increases making it difficult to move and decreasing its velocity.
Step IV: This is the same as the working of Bernoulli’s Law.
Option B is the correct answer.

Note:Bernoulli’s Law has a wide variety of applications in different fields these days. Some of the examples where Bernoulli’s Law is seen are:
1) The wings of the airplane are made in a way that they follow Bernoulli’s Principle so as to fly efficiently. Because air pressure is more above the wings than below. That is why the wings of the airplane have a curved shape.
2) Bernoulli’s principle also helps in explaining why a person tends to fall towards the train while standing on a railway platform.