Question

Which of the following cannot be explained on the basis of Bernoulli’s principle?
A. Lift on an aircraft’s wing.
B. Ink filler
C. Swing of a cricket ball
D. Atomizer

Answer 1

To answer this question let us discuss pressure and velocity. The relationship between pressure and velocity is inverse. As pressure rises, velocity falls in order to maintain the algebraic sum of potential energy, kinetic energy, and pressure.

Complete answer:
In order to answer this question let us first understand the Bernoulli’s Principle. Bernoulli's principle is an idea of fluid dynamics. It says that as the speed of the fluid increases, pressure decreases. A higher pressure pushes (accelerates) fluid toward lower pressure. So any change in a fluid's speed must be matched by a change in pressure (force).

Now let see which of the options satisfy Bernoulli’s Principle. With the aid of lift on its wings, an aircraft wing changes its vertical position. The area below the wing is under high pressure, while the area below the wing is under low pressure. This pressure difference causes the uplift.

Surface friction and pumps are used to make Ink Filler work. The ink in the bottle is drawn to the pen by the vacuum in the pen. Surface friction causes the ink to flow through the small opening in the pen tip (to minimise the surface area). The pressure differential generated on the two sides of the ball due to initial spin controls the swing of a cricket ball.

Bernoulli's theory is used to create an atomizer. When a swift gas stream is pumped into the atmosphere and over the top of a vertical tube, it is forced to follow a curved path on the other side of the tube up, across, and downward. The inside of the curve at the top of the tube is subjected to less pressure due to the curved direction. The net force is the difference between the lower pressure near the tube created by the curve and the ambient pressure higher up.

So option B is correct.

Note: Bernoulli's theorem can be generalised to various types of fluid flow, resulting in various forms of Bernoulli's equation; different types of flow result in different forms of Bernoulli's equation. For incompressible flows, Bernoulli's equation in its simplest form is valid. At higher Mach numbers, more advanced forms can be applied to compressible flows.