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Physics · MOTION IN A STRAIGHT LINE
हिन्दीA bullet moving with initial speed \( v_0 \) penetrates a wooden block and loses \( 20\% \) of its speed after penetrating a distance of \( 9\text{ cm} \). Assuming uniform deceleration inside the block, how much further distance will the bullet penetrate before coming to rest?
Correct answer · Option 2
\( 16\text{ cm} \)
Explanation
Remaining speed \( v_1 = 0.8 v_0 \). Using \( v_1^2 - v_0^2 = 2 a x_1 \implies (0.64 - 1)v_0^2 = 2a(9) \implies a = -\frac{0.36 v_0^2}{18} = -0.02 v_0^2 \). For rest from \( v_1 \): \( 0^2 - (0.8v_0)^2 = 2a x_2 \implies -0.64 v_0^2 = 2(-0.02 v_0^2) x_2 \implies x_2 = 16\text{ cm} \).
