Collision: Practice Problem & Solution
Body A of mass $4m$ moving with speed $u$ collides with another body B of mass $2m$, at rest. The collision is head-on and elastic in nature. After the collision the fraction of energy lost by the colliding body A is: (2019)
Short Solution (Best for NEET):
To solve this problem, we apply the core principles of Collision. Understanding the underlying formula is key to arriving at the correct answer below:
Final velocity of A is $v_1 = \frac{m_1 - m_2}{m_1 + m_2}u = \frac{1}{3}u$. Fraction of energy lost is $1 - \left(\frac{v_1}{u}\right)^2 = 1 - \frac{1}{9} = \frac{8}{9}$.
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