Question
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