Two identical balls, A and B, are moving towards each other at V1 and V2. They collide head-on. Which of the following is incorrect if the collision is elastic?
A. The balls move away from each other after collison.
B. After collision, A moves at V2 and B moves at V1.
C. Sound will be given out during collision.
D. During the impact, there are forces acting on A and B.
Ans: C
Please explain why A,B and D are correct and C is incorrect?