Answer
given,
mass of base ball = 0.14 kg
speed before it made the contact with the ball (V i) = 42 m/s
speed after batter hit the ball(V f) = - 48 m/s
a)
impulse = change in momentum
=
=
= -12.6 Kg m/s
Magnitude of impulse = 12.6 Kg m/s
b)
Force = 
= 
Force = 2520 N
Sound travels at approximately 1,100 feet per second (766 miles per hour). Radio waves travel at the speed of light, which is approximately 186,000 miles per second. This means that in the time radio waves travel the length of a football field, light can travel further than all the way around the world.
I would say friction because it requires to surfaces in order for the force to take place
correct me if I'm wrong.