Q 11-05-043NEETJEE MainMedium
A $2$ kg ball moving at $6$ m/s collides head-on elastically with a $4$ kg ball at rest. The velocities of the two balls after the collision are
Answer: (B) $-2$ m/s and $4$ m/s
Concept. Elastic head-on, target at rest: $v_1 = \dfrac{m_1 - m_2}{m_1 + m_2}u$, $v_2 = \dfrac{2m_1}{m_1 + m_2}u$.
Step 1. Velocities. $v_1 = -2$ m/s, $v_2 = 4$ m/s.
Answer. $-2$ m/s and $4$ m/s (Option B).
Solution by Sreeraj P, M.Sc Physics