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JEE Main 24 February 2021, Shift 2, Physics Q3

Question 3 of 90 in this shift, Physics question 3 of 30, Section A.

A circular hole of radius

\left(\frac{a}{2}\right)

is cut out of a circular disc of radius 'a' as shown in figure. The centroid of the remaining circular portion with respect to point 'O' will be :

The figure, in words

Large circle with a vertical Y-axis (arrow up, labelled Y-axis) tangent to its left edge; the point O is labelled where the Y-axis meets the horizontal X-axis (arrow right, labelled X-axis) at the left edge of the circle. A dot on the X-axis, at a distance marked 'a' from O (arrow labelled a from O), and a second dot further right on the X-axis; a smaller circle is drawn inside the large circle, touching it at the right end of the X-axis, with its radius marked 'a/2' by a dotted arrow. The first dot lies at the left end of the small circle and the second dot at its centre.

(1) $\frac{1}{6}a$
(2) $\frac{5}{6}a$ Official answer
(3) $\frac{2}{3}a$
(4) $\frac{10}{11}a$

Official answer

Option 2

NTA final key.

Chapter: System of Particles and Rotational Motion
Topic: Center of Mass
Idea tested: COM of Composite Bodies

JEE Main 24 February 2021, Shift 2, Physics Q3

Same idea in other shifts