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The bullet with mass $$m_{ball}=0.2 kg$$ travels with speed $$v=2 \frac{m}{s}$$ and hits Plasticine sphere with mass $$m_{sphere}=2.5 kg$$ and get stuck. I need to find the amount of heat ejected. How to approach this task? Probably it's about kinetic energy transforming to heat; and the law of conservation of momentum.

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closed as off-topic by jinawee, Brandon Enright, John Rennie, Kyle Kanos, user10851 Mar 13 '14 at 6:08

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The velocity of the system after collision is $$ V=\frac{m_b}{m_b+m_s}v_b $$

The lost of kinetic energy can be assumed as the ejected heat in question, \begin{align} \Delta KE &= m_b v_b^2 /2 - (m_b+m_s)V^2 /2\\ &= m_b v_b^2 /2 - \frac{m_b^2}{m_b+m_s}v_b^2 /2\\ &= m_b v_b^2/2 \left(1-\frac{m_b}{m_b+m_s} \right)\\ &= \frac{m_b m_s}{m_b+m_s}v_b^2/2 \\ \end{align}

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