You can hit an underhand serve in tennis; however, the overhand serve is more effective because it is more powerful. That is why you don't see the underhand serve used much.
watch this video and it show you http://www.youtube.com/watch?v=4NwwrtCH3PU
this depends on how skilled you are.
Serving in badminton is opposite from the form used in tennis. To serve, hold the bird in one hand and hold the racket below it. Then drop the birdie and hit the center of the rubber tip with an underhand motion.
Badly.
a serve
A tennis ball!
no you might just want to drop it so you can hit it up and it is called an underhand serve
a tennis ball
A tennis ball.
A TENNIS BALL.
a fault
a serve