The bullet, having pierced the board, reduced its speed by half. How many percent of its initial kinetic energy was converted into heat and deformation energy?
Data: V1 (speed of the bullet before piercing the board) = 2V2 (speed at the exit from the board).
To find the percentage of the initial kinetic energy of a given bullet, converted into deformation energy and heat, we use the ratio: η = 1 – Ek2 / Ek1 = 1 – 0.5 * m * V2 ^ 2 / (0.5 * m * V1 ^ 2 ) = 1 – V2 ^ 2 / 4V2 ^ 2 = 1 – 0.25 = 0.75 or 75%.
Answer: 75% of the initial kinetic energy of a given bullet passed into the deformation energy and heat.
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