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A lead bullet has initial temperature 27C,melting point 327C,latent heat at melting...

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lak-86 | Student, Undergraduate | Salutatorian

Posted June 27, 2013 at 9:22 AM via web

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A lead bullet has initial temperature 27C,melting point 327C,latent heat at melting 2.1x10^4J/kg and specific heat capacity of 126J/(kgC). Assuming that all the kinetic energy convert to heat calculate the speed of a bullet that hit a steel slab.

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted June 27, 2013 at 9:40 AM (Answer #2)

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As given in the question kinetic energy of the bullet convert to heat energy.

kinetic energy of bullet (`E_k`  ) will be equal to the sum of heat required to get the bullet to melting point(`Q_m` ) and latent heat required for melting (`Q_l ` )

 


`E_k = Q_m+Q_l` 

 

Assume that bullet has a mass of m.

 

`E_k = 1/2xxmxxv^2`

 

 

 

`Q_m = mxx126xx(327-27) = mxx126xx300`

 


`Q_l = mxx2xx10^4 `

 

 

 

`1/2xxmxxv^2 = mxx126xx300+mxx2xx10^4 `

 

`v^2 = 2(126xx300+20000) `

 

`v^2 = 115600 `

 

`v = 340m/s`

 

 

 

So the bullet need to strike the steel at a velocity of 340m/s.

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted June 27, 2013 at 9:52 AM (Reply #1)

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in the above answer equations doesn't appeared properly. please refer below answer.

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