Super Noob Question: Do grenades rolling around on the ground case damage?

I play spy pretty much exclusively (I tried medic yesterday and accidentally ubered our other medic, which shows my mad skills at other classes) and was wondering if grenades rolling on the ground cause damage.  I avoid them since they do blow up, but I also read that grenades need to be a direct hit (
i.e., they only damage people when hitting them on the fly). 

Thanks!

If your talking about the Demo man's grenades then yes they do expolde after hitting the ground and still do damage, im not sure if its more or the same but all i know is that iv gotten alot of kill's with demo spam.

Grenades only damage on direct hit or when they automatically detonate. They will cease to detonate on contact after the first bounce.

Grenades are like rockets when they blow up.  avoid them.  There is a radius of damage that has a falloff or decay around the center of the grenade - the further you are from them the less damage they do.

edit - The difference though of course is they obviously have a different trajectory, and the soldier's rocket does less damage if it is launched from further away, the pipe bomb does the same amount of damage no matter how far the lob is.

If the grenade rolls near you and blows up you get hurt. I don't think it hurts you as much as a direct hit though.

Edit: Ninja'd