Question

why do fielders lower their hands whilde catching a fast moving ball?

Answer 1

so that the force felt by then become lower.
as we know impulse=force×time
so force=impulse/time
so as the time increases we feel less force so this is why feilders lower their hand

Answer 2

because momentum increases when a body travels shorter distance and decreases when it travels longer distance. similarly a bowler lower their hands while catching a fast moving ball to increase the distance and lower the momentum. lower the momentum less is the hurt got by him and vice versa. so it is moved to increase the distance and to prevent injury