How fast should the bullet fly so that it melts completely when it hits the wall? The melting point of a bullet

| August 1, 2021 | education

How fast should the bullet fly so that it melts completely when it hits the wall? The melting point of a bullet is 600 K, the specific heat is 125 J / kgK, and the specific heat of fusion is 2.5 · 104 J / kg. Consider the temperature of the bullet before the impact was 50 C and that it received all the released energy.

To calculate the required bullet speed, we use the equality: m * V ^ 2/2 = Cп * m * (tpl – t0) + λ * m, whence V = √ (2 * (Cп * (tpl – t0) + λ) ).

Values of variables: Cп – heat capacity of the bullet metal (Cn = 125 J / (kg * K)); tmelt – melting point (tmelt = 600 K = 327 ºС); t0 – bullet temperature before impact (t0 = 50 ºС); λ – specific heat of fusion (λ = 2.5 * 10 ^ 4 J / kg).

Let’s calculate: V = √ (2 * (Cp * (tpl – t0) + λ)) = √ (2 * (125 * (327 – 50) + 2.5 * 10 ^ 4)) = 345.3 m / with.



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