A firework that is initially at rest detonates and breaks into two fragments, which then travel horizontally in opposite directions. The explosion transfers a total kinetic energy of $E$ to the fragments. One fragment has mass $m$ and the other has mass $2m$. What is the speed of the fragment of mass $m$ immediately after the explosion?
- A$\sqrt{\frac{E}{m}}$
- B$\sqrt{\frac{2E}{m}}$
- C$\sqrt{\frac{2E}{3m}}$
- D$\sqrt{\frac{4E}{3m}}$