Question

What's the spring constant based on the given quantities?
http://i42.tinypic.com/1z68ioi.png shows the quantities.

A) mv^2/A^2
B) Mv^2/A^2
C) m^2v^2/(m+M)A^2
D) (M+m)^2v^2/mA^2

Thank you!

Answer 1

The initial energy of the system is: mv^2/2
The final energy is: 0+kA^2/2
Equate and get your answer.

Answer 2

kinetic energy of bullet is converted to ==== potential energy of spring (by displacing it)