It has been said that sometimes lead bullets melt upon impact. Assume that a bul

Question

It has been said that sometimes lead bullets melt upon impact. Assume that a bullet with an initial temperature of 3.00?102K receives 62.9% of the work done on it by a wall on impact as an increase in internal energy.

a) What is the minimum speed with which a 14.9?g lead bullet would have to hit a surface (assuming the bullet stops completely and all the kinetic energy is absorbed by it) in order to begin melting?

b) What is the minimum impact speed required for the bullet to melt completely?

please show work

Explanation / Answer

a] Consider the initial velocity to be V

Then KE is .5mV^2 right? m=14.9/1000 Kg

Now, to begin melting the temperature of the bullet has to reach 300 K from 293 K. You need the specific heat of lead to find the total heat required.


Effective energy increasing lead's internal energy is 62.9% of the total KE of the bullet after impact on wall which you've already determined.

so .5 *m* V^2 = m * C * (300 - 293)

from here you should get V.

b) In order to melt completely, you need not only the previous energy to heat the bullet to 300K but also the latent heat to actually melt it completely.

So energy required = m*C*(300-293) + m*L (latent heat of fusion)

Relate this to 62.9% of .5*m* v' ^2 and find v'.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.