Yesterday, one of my cousins asked me about Newton's third law. In this discussion he asked me this question: Why does not a bullet bounce back after striking the surface of glass as it does in the case of steel, considering that in both the cases the force with which it strikes the glass or steel is equal to the force applied by the glass or steel to the bullet? I gave him a long explaination but he was not convinced (even I wasnt convinced ). At night when I went to the bed I thought about my explaination and found that it was greatly flawed. Can anyone please explain this to me? Secondly, How can I find the force with which a bullet of mass m kg strikes a surface of an object with the constant velocity of v m/s? I know the kinetic energy at that instant will be (1/2)mv^2. Dont know where to go from here. Thanks alot in advance. Abd. S.