KEAM Centre of Mass — practice questions

Explore 2 free Centre of Mass questions in KEAM Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Centre of Mass questions and exercises with answers

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Two point particles of equal mass are placed at x = 2 m and x = 8 m on the x-axis. Where does the centre of mass of the system lie?Read the answer and worked solution →For a homogeneous (uniformly dense) thin circular disc, the centre of mass lies at:Read the answer and worked solution →

Worked practice questions

Two point particles of equal mass are placed at x = 2 m and x = 8 m on the x-axis. Where does the centre of mass of the system lie?

x = 4 m
x = 5 m
x = 6 m
x = 10 m

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Correct answer: B. x = 5 m

For two equal masses, the centre of mass lies exactly midway between them: X = (x1 + x2)/2 = (2 + 8)/2 = 5 m.

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For a homogeneous (uniformly dense) thin circular disc, the centre of mass lies at:

Any point on the circumference
Its geometric centre
A point depending on its orientation
A point on the axis but outside the plane of the disc

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Correct answer: B. Its geometric centre

A homogeneous disc has reflection symmetry about its geometric centre: for every mass element at (x, y) there is an equal element at (−x, −y). The symmetry integrals $\int x \, dm$ and $\int y \, dm$ both vanish about that point, so the COM coincides with the geometric centre. This argument holds for all uniformly dense regular shapes (ring, sphere, rod, etc.).