# phys

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A 30.0-g lead bullet leaves a rifle at a temperature of 89.0° C and hits a steel plate. If the bullet melts, what is the minimum speed it must have?

• phys -

Latent heat of melting r = 22400 J/kg, specific heat c =130 J/kg•oC
Q = m•c•Δt + r•m = m•(c•Δt + r) =
= 0.03•( 130•(327-89) + 22400) =1600 J.
m•v^2/2 = Q
v = sqrt (2•Q/m) =sqrt (2• 1600/0.03) =326 m/s.

• phys -

327

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