Topic sentence - baseballs hit with metal bats travel at a higher rate of speed than those hit with wooden bats
concrete facts - trampoline effect, new york times reported that baseballs hit with metal bats travel almost 20mph faster than baseballs hit with wooden bats
commentary - this is a huge difference to a player trying to make a play on a line drive in time, this happens so fast pitchers and infielders don’t have time to react, which places them in danger.
Hope this helped and made sense