A 5.0 g lead bullet is fired into a fence post. The initial speed of the bullet is 210 m/s, and when it comes to rest, half its kinetic energy goes into heating the bullet. How much does the bullet's temperature increase?

Question

Physics

Saul Hancock

10 December, 18:18

A 5.0 g lead bullet is fired into a fence post. The initial speed of the bullet is 210 m/s, and when it comes to rest, half its kinetic energy goes into heating the bullet. How much does the bullet's temperature increase?

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Malakai Grimes · Answer 1

5g = 0.005 kg

So KE=1/2 0.005 kg * 210m/s^2 = 110 J.

Now the specific heat capacity of lead is 126 J/kgK, so the temperature change = 55 J / 0.005 * 126 J/kgK=87.3015873 K. Which, if normal thermal conditions, the bullet would have a temperature of around 360,451587 Kelvin or, simplified, 107.3 degrees celsius.