A shell in air explodes into n equal fragments, k of the fragments reach the ground earlier than the other…

A shell in air explodes into n equal fragments, k of the fragments reach the ground earlier than the other fragments. The acceleration of their centre of mass subsequently will be
  1. g
  2. n-kg
  3. n-kgk
  4. n-kng

Solution

acm=ΣmiaiΣmi

Till all the particle remains in air center of mass remains stationary. When k particles hit the ground then center of mass shifts with accelaration :

acm=n-kng

Asked in: Practice

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