A cannon ball is fired with a velocity 200

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A cannon ball is fired with a velocity $200\, m/sec$ at an angle of $60° $ with the horizontal. At the highest point of its flight it explodes into $3$ equal fragments, one going vertically upwards with a velocity $100 \,m/sec$, the second one falling vertically downwards with a velocity $100\, m/sec$. The third fragment will be moving with a velocity

A

$100\, m/s$ in the horizontal direction

B

$300\, m/s$ in the horizontal direction

C

$300 \,m/s$ in a direction making an angle of $60°$  with the horizontal

D

$200\, m/s$ in a direction making an angle of $60°$  with the horizontal

A cannon ball is fired with a velocity $200\, m/sec$ at an angle of $60° $ with the horizontal. At the highest point of its flight it explodes into $3$ equal fragments, one going vertically upwards with a velocity $100 \,m/sec$, the second one falling vertically downwards with a velocity $100\, m/sec$. The third fragment will be moving with a velocity

Let the velocity of third part after explosion is$  V$
After explosion momentum of system = ${\vec P_1} + {\vec P_2} + {\vec P_3}$
= $\frac{m}{3} \times 100\hat j - \frac{m}{3} \times 100\hat j + \frac{m}{3} \times V\hat i$
By comparing momentum of system before and after the explosion
$\frac{m}{3} \times 100\hat j - \frac{m}{3} \times 100\hat j + \frac{m}{3}V\hat i = 100m\hat i$

==>$V = 300\,m/s$