The answer is reflection.
Answer:
Explanation:
From the question we are told that mass
Thin layer radius 
Generally the expression for ths solution is given as
Xcm =(m*0 =m(-2R))/2m =-mR/(2m)=-R/2
the center of mass will not move at initial state
Considering the center of mass of both bodies


Therefore the enclosing layer moves
Before the impact, let the velocity of the baseball was v m/s.
After being hit by the bat its velocity is -2v
So, change in velocity, Deltav=v-(-2v)=3v
Acceleration is defined as the rate of change in velocity, i.e. actual change in velocity divided by the time taken to change it. Time taken to change velocity is the time of actual contact of the bat and ball, i.e. 0.31 s.
a=(Deltav)/(Deltat)
=(3v)/0.37
Therefore, a/v=3/0.31=9.7 s^-1
So, the ratio of acceleration of the baseball to its original velocity is 9.7.