NEET-XII-Physics
qstns with ansrs year:2022
- #20A shell of mass `` m `` is at rest initially. It explodes into three fragments having mass in the ratio `` 2: 2: 1 `` . If the fragments having equal mass fly off along mutually perpendicular directions with speed `` v `` , the speed of the third (lighter) fragment is :
(A) `` 3 \sqrt{2} v ``
(B) `` v ``
(C) `` \sqrt{2} v ``
(D) `` 2 \sqrt{2} v ``digAnsr: DAns :
By conservation of momentum :
`` m(0)=\frac{2 m}{5}(-v \hat{i})+\frac{2 m}{5}(-v \hat{j})+\frac{m}{5} \vec{v}^{\prime} ``
`` \Rightarrow \vec{v}^{\prime}=2 v \hat{i}+2 v \hat{j} ``
`` \Rightarrow v^{\prime}=\sqrt{(2 v)^{2}+(2 v)^{2}} ``
`` =2 \sqrt{2} v ``