Question

An object of mass $40\, kg$ and having velocity $4\, m s^{-1}$ collides with another object of mass $60\, kg$ having velocity $2 \,ms^{-1}$. The loss of energy when the collision is perfectly inelastic

• A. 392 J
• B. 440 J
• C. 110 J
• D. 48 J

Answer 1

Answer: (D)

48 J

Answer 2

Using $\upsilon = \frac{m_1u_1 + m_2u_2}{m_1+m_2}$ , we get $\upsilon = \frac{40\times 4 + 60 \times 2}{40 + 60} = 2.8 \, m \, s^{-1}$ Loss of energy = $\frac{1}{2} [m_1u^2_1 + m_2 u^2_2] - \frac{1}{2} (m_1 + m_2) \upsilon^2$ = $\frac{1}{2} [ 40 \times 16 + 60 \times 4 - 100(2.8)^2]$ = 48 J