Physics

Problem

A stationary body breaks into two fragments of masses

2\,\text{kg}

and

3\,\text{kg}

. The

2\,\text{kg}

fragment moves to the right with a speed of

6\,\text{m\,s}^{-1}

. What is the speed of the

3\,\text{kg}

fragment? a)

9\,\text{m\,s}^{-1}

to the left b)

4\,\text{m\,s}^{-1}

to the right c)

4\,\text{m\,s}^{-1}

to the left d)

2.4\,\text{m\,s}^{-1}

to the left

Intuitive explanation

This is a conservation of momentum problem: since the original body was at rest, the total momentum before the break must equal zero, so the two fragments must move in opposite directions with momenta that cancel. Use the fact that $m_1 v_1 + m_2 v_2 = 0$ to find the unknown velocity—the heavier fragment will move slower and backward to balance the lighter one's forward motion.

Intuitive explanation

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