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Question: A straight rod of length 9 units slides with with its ends A, B always on the x and y axis respectiv...

A straight rod of length 9 units slides with with its ends A, B always on the x and y axis respectively . Then the locus of centroid of D OAB is-

A

x2 + y2 = 3

B

x2 + y2 = 9

C

x2 + y2 = 1

D

x2 + y2 = 81

Answer

x2 + y2 = 9

Explanation

Solution

Let (x, y) be the centroid of D OAB

x = a/3, y = b/3 i.e. a = 3x , b = 3y

But AB = 9 unit

\ a2 + b2 = 81 Ž 9x2 + 9y2 = 81Ž x2 + y2 = 9