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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



Question ID - 100736 | SaraNextGen Top Answer

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
127 votes
Answer Key / Explanation : (c) -

(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

127 votes


127