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NEET2009PhysicsCenter of Mass, Momentum and CollisionActual

Two bodies of mass 1 ~kg and 3 ~kg have position vectors i +2 j + k and -3 i -2 j + k , respectively. The centre of mass of this system has a position vector

Options

  1. A-2 i +2 k
  2. B-2 i - j + k
  3. C2 i - j -2 k
  4. D- i + j + k

Correct answer

B. -2 i - j + k

Step-by-step solution

The position vector of centre of mass aligned r & = m₁ r₁ +m₂ r ₂ m₁+m₂ & = 1( i +2 j + k )+3(-3 i -2 j + k ) 1+3 & = 1 4 (-8 i -4 j +4 k ) & =-2 i - j + k aligned The centre of mass changes its position only under the translatory motion. There is no effect of rotatory motion on centre of mass of the body.

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