A platform diver holds his hands and legs straight and makes loops in

1.	A platform diver holds his hands and legs straight and makes loops in air before entering into water.1. State the principle behind this.2. What happens when he tries to land in the pool by stretching his arms and legs?3. In the above situation, rotational kinetic energy is not conserved. Explain.
Answer» 1. Conservation of angular momentum Statement Conservation of angular momentum states that, if the total torque acting on a system is zero, its angular momentum will be conserved. 2. Angular velocity decreases. 3. Initial kinetic energy K.E₁ = \(\frac{L^2}{2I_1}\) ____(1) where I₁ is the moment of inertia of diver when he makes loops in air final kinetic energy K.E₂ = \(\frac{L^2}{2I_2}\) _____(2) where I₂ is the moment of inertia of diver when he stretches his hands But I₁ < I₂ Hence from eq(1) and eq(2), we get KE₁ > KE₂ which means that rotational kinetic is not conserved.

A platform diver holds his hands and legs straight and makes loops in air before entering into water.1. State the principle behind this.2. What happens when he tries to land in the pool by stretching his arms and legs?3. In the above situation, rotational kinetic energy is not conserved. Explain.

Answer»

1. Conservation of angular momentum

Statement

Conservation of angular momentum states that, if the total torque acting on a system is zero, its angular momentum will be conserved.

2. Angular velocity decreases.

3. Initial kinetic energy K.E₁ = \(\frac{L^2}{2I_1}\) ____(1)

where I₁ is the moment of inertia of diver when he makes loops in air

final kinetic energy K.E₂ = \(\frac{L^2}{2I_2}\) _____(2)

where I₂ is the moment of inertia of diver when he stretches his hands

But I₁ < I₂

Hence from eq(1) and eq(2), we get

KE₁ > KE₂

which means that rotational kinetic is not conserved.

Discussion

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