The problem in the image involves two objects with the same mass $m_1 = m_2 = 2 \, \text{kg}$, moving towards each other. The velocities before the collision are $v_1 = 10 \, \text{m/s}$ and $v_2 = 20 \, \text{m/s}$, and the collision is described as a perfectly elastic collision ("tumbukan lenting sempurna").

Key points for solving:

1. Conservation of Momentum: In any collision, momentum is conserved. $m_1 v_1 + m_2 v_2 = m_1 v_1' + m_2 v_2'$ where $v_1'$ and $v_2'$ are the velocities after the collision.

2. Conservation of Kinetic Energy: For a perfectly elastic collision, kinetic energy is also conserved. $\frac{1}{2} m_1 v_1^2 + \frac{1}{2} m_2 v_2^2 = \frac{1}{2} m_1 v_1'^2 + \frac{1}{2} m_2 v_2'^2$

Since $m_1 = m_2$, and after simplifying the system of equations, we can use the following formula for a perfectly elastic collision between two objects of equal mass: $v_1' = v_2$ $v_2' = v_1$

Applying the Formula:

• Before the collision: $v_1 = 10 \, \text{m/s}, \quad v_2 = 20 \, \text{m/s}$
• After the collision (since $m_1 = m_2$): $v_1' = v_2 = 20 \, \text{m/s}, \quad v_2' = v_1 = 10 \, \text{m/s}$

Conclusion:

The correct answer is option e:
$v_1' = 5 \, \text{m/s} \quad v_2' = 10 \, \text{m/s}$.

Let me know if you'd like further clarification or have additional questions!