A 10 kg sphere (at A) is connected to a 5 kg sphere (at E)by a rigid rod of negl
ID: 1786391 • Letter: A
Question
A 10 kg sphere (at A) is connected to a 5 kg sphere (at E)by a rigid rod of negligible mass as shown itn the figure. Treat each sphere as a particle. B C D Use for problems 1, 2 and 3 1 Which of the five lettered points best represents the center of mass of the sphere-rod combination? A. A B. B C. C D. D E. E The sphere-rod combination can be pivoted about an axis that is perpendicular to the plane of the page and that passes through one of the five lettered points. Through which point should the axis pass for the moment of inertia of the sphere-rod combination about this axis to be greatest? 2- A. A B. B C. C D. D E. E 3 The sphere-rod combination can be pivoted about an axis that is perpendicular to the plane of the page and that passes through one of the five lettered points. Through which point should the axis pass for the moment of inertia of the sphere-rod combination about this axis to be smallest? A. A B. B C.C D. DExplanation / Answer
1. The answer is option B
Reason: The center of mass of the sphere-rod combination is shifted away from the middle point C
towards the heavier mass of 10 kg which is at point B.
2. The answer is option E i.e at point E where 5kg mass is connected
Reason: The pivot point which will always reduce the rotational inertia is the one passing through the center of
mass. The farther we get from the center of mass, the greater is the rotational inertia. The center of mass of
the system is at point B. Therefore we need to pivot the system about point E.in order to get the moment of
inertia of the sphere-rod combination about this axis to be greatest.
3. The answer is option B.
Reason: The pivot point which will always reduce the rotational inertia is the one passing through the center of
mass. This means that the moment of inertia of the sphere-rod combination about this axis will be smallest at
point B which is the center of mass of the sphere-rod combination.
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