Physics

A bullet is moving with velocity u after emerging from a plank
its velocity reduces by u/20 then find the total number of planks required to stop this bullet?

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  1. u - u/20 = 19u/20 = .95u

    .95² = .9025

    the bullet loses about 10% of its energy (kinetic), as work passing through the plank

    it should stop in the 11th plank

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