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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Rotational Mechanics

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Rotational Mechanics

A diver with a moment of inertia of 6.0 kg-m^2 about an axis...

A diver with a moment of inertia of 6.0 kg-m26.0 \text{ kg-m}^2 about an axis passing through his centre of mass rotates about this axis at an angular speed of 2 rad/s2 \text{ rad/s}. If the diver folds his hands and feet, reducing the moment of inertia to 5.0 kg-m25.0 \text{ kg-m}^2, what will be the new angular speed?

Options

  1. A1.2 rad/s1.2 \text{ rad/s}
  2. B2.4 rad/s2.4 \text{ rad/s}
  3. C1.67 rad/s1.67 \text{ rad/s}
  4. D4.8 rad/s4.8 \text{ rad/s}

Correct answer

B. 2.4 rad/s2.4 \text{ rad/s}

Step-by-step solution

According to the principle of conservation of angular momentum, if no external torque acts on a system, its total angular momentum remains constant.

Initial angular momentum L1=I1ω1L_1 = I_1 \omega_1

Final angular momentum L2=I2ω2L_2 = I_2 \omega_2

Equating the initial and final angular momentum:

I1ω1=I2ω2I_1 \omega_1 = I_2 \omega_2

Substituting the given values:

6.0×2=5.0×ω26.0 \times 2 = 5.0 \times \omega_2

ω2=12.05.0=2.4 rad/s\omega_2 = \dfrac{12.0}{5.0} = 2.4 \text{ rad/s}
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