Two point masses of 0.3 kg and 0.7 kg are fixed at the ends of a rod of length 1.4 m and of negligible mass. The rod is set rotating about an axis perpendicular to its length with a uniform angular speed. The point on the rod through which the axis should pass in order that the work required for rotation of the rod is minimum is located at a distance of |
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a) |
0.42 m from the mass of 0.3 kg |
b) |
0.70 m from the mass of 0.7 kg |

c) |
0.98 m from the mass of 0.3 kg |
d) |
0.98 m from the mass of 0.7 kg |

Two point masses of 0.3 kg and 0.7 kg are fixed at the ends of a rod of length 1.4 m and of negligible mass. The rod is set rotating about an axis perpendicular to its length with a uniform angular speed. The point on the rod through which the axis should pass in order that the work required for rotation of the rod is minimum is located at a distance of |
|||

a) |
0.42 m from the mass of 0.3 kg |
b) |
0.70 m from the mass of 0.7 kg |

c) |
0.98 m from the mass of 0.3 kg |
d) |
0.98 m from the mass of 0.7 kg |

1 Answer

5876 Votes

3537

**(c)**

The moment o inertia of the system about axis of rotation is

+

The work done in rotating the rod is converted into its rotational kinetic energy

For work done to be minimum

Let be the moment of inertia of a uniform plate about an axis that passes through its centre and is parallel to two of its sides. is a line in the plane of the plate that passes through the centre of the plate and makes an angle with . The moment of inertia of the plate about the axis is then equal to |
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a) |
b) |
c) |
d) |

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