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Q.(a) State Torricelli's principle. Derive the formula of velocity of efflux.

(b) Explain Magnus effect and heart attack. OR State Bernoulli's principle. Derive the Bernoulli's equation. Draw the necessary diagram.
Rajasthan RbseRajasthan Board Senior Secondary Part-I Examination 2017Subjective· 5mImportance★★★★★
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Torricelli's principle (v = √(2gh) for efflux speed) is a special case of Bernoulli's equation; the Magnus effect and Bernoulli's role in heart attacks are both real-life applications of the same principle: faster flow means lower pressure. (This solves the primary question; the OR alternative on Bernoulli's principle/equation is not separately required.)

  1. Torricelli's Principle and Velocity of Efflux: Consider a wide tank filled with liquid up to height h above a small orifice (hole) near the bottom. Applying Bernoulli's equation between a point (1) at the free surface and a point (2) at the orifice, both open to the atmosphere (so both are at atmospheric pressure P0): P0 + ρg y1 + (1/2)ρ v1^2 = P0 + ρg y2 + (1/2)ρ v2^2 Since the tank is wide, the free surface falls very slowly, so v1 ≈ 0. Taking y1 - y2 = h (height of liquid column above the hole): ρg h = (1/2)ρ v2^2 v2 = √(2gh) This is Torricelli's principle: the speed with which liquid emerges from a small hole at depth h below the free surface equals √(2gh) — exactly the speed a body would acquire falling freely (under gravity alone) through the same height h.
  2. Magnus Effect and Heart Attack (applications of Bernoulli's principle): Magnus effect: When a ball spinning about an axis moves through air, the air near the surface of the ball is dragged along with the spin (due to viscosity), so on one side the ball's spin ADDS to the relative air speed (higher speed, hence lower pressure by Bernoulli's principle) while on the other side the spin OPPOSES the airflow (lower relative speed, hence higher pressure). This pressure difference across the ball produces a net sideways force on it, curving its path — this is the Magnus effect, and it's why a spinning cricket/tennis ball swings or curves in flight. …

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