AFMC AFMC Solved Paper-2001

  • question_answer
    A body of mass M at rest explodes into three masses two of which of mass\[\frac{M}{4}\]each are thrown off in perpendicular directions with velocity of 3m/sand 4 m/s respectively. The third piece will be thrown off with a velocity of :

    A) 3 m/s                                    

    B) 2.5 m/s

    C) 2.0 m/s                                

    D) 1.5 m/s

    Correct Answer: B

    Solution :

    Key Idea: Momentum of system remain conserved in universe. From law of conservation of momentum the total momentum of the system is conserved. Given, mass of body is M, mass of two  particles \[\frac{M}{4}\times 2=\frac{M}{2}\] Hence, mass of third piece is\[\frac{M}{2}.\] Also since particles are thrown off in perpendicular directions, vector sum of the momentum of the first two pieces is numerically equal but opposite in direction to the momentum of third piece. \[v\left( \frac{M}{2} \right)=\sqrt{{{\left( \frac{3M}{4} \right)}^{2}}+{{\left( \frac{4M}{4} \right)}^{2}}}\] \[\Rightarrow \]   \[v=2.5\,m/s\]


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