Answer:
Part a)

Part b)

Explanation:
Since the ball and rod is an isolated system and there is no external force on it so by momentum conservation we will have

here we also use angular momentum conservation
so we have

also we know that the collision is elastic collision so we have

so we have

also we know

also we know

so we have


now we have


Part b)
Now we know that speed of the ball after collision is given as

so it is given as

6.022*10^23 atoms/mole of reactant
(this is chemistry not physics)
Hope it helped you.
My name is Charlie.
Today this question is about science,or chemistry.
A. Acceleration is a correct answer. Acceleration is a rate of change in velocity.
It change in velocity/change in time. Next, to slope will be indicated by the acceleration.
B Change in position is a incorrect answer.
C. Velocity is a incorrect answer. Velocity is a displacement of an object during a specific unit of time. It can used two measurements are needed to determine velocity. It displacement or by the time. Displacement it includes a direction, so the velocity will also includes a direction. It can used speed with direction. Velocity it can be average velocity or an instantaneous velocity.
-Charlie
Have a great day!
Thanks!