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Physics · PYQ NEET UG 2016(2)
हिन्दीA bullet of mass \( 10\text{ g} \) moving horizontally with a velocity of \( 400\text{ ms}^{-1} \) strikes a wooden block of mass \( 2\text{ kg} \) which is suspended by a light inextensible string of length \( 5\text{ m} \). As a result, the centre of gravity of the block found to rise a vertical distance of \( 10\text{ cm} \). The speed of the bullet after it emerges out horizontally from the block will be
Correct answer · Option 1
\( 160\text{ ms}^{-1} \)
Explanation
Use conservation of momentum and energy. Block velocity \( V = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 0.1} \approx 1.4\text{ m/s} \). By momentum conservation: \( m v_1 = m v_2 + M V \). Solving gives \( v_2 = 160\text{ ms}^{-1} \).
