Questions in regards to momentum

[angel_romano]

If you throw a ball horizontally while standing still on roller skates, you roll backwards. Will you roll backwards if you go through the motions of throwing the ball, but hold on to it instead?

And is it difficult for a fire fighter to hold a hose that ejects large amounts of high-speed water since it's momentum pushes the firefighter in the opposite direction, with the same momentum...or is it different?

 

[moose]

For the first one, think about systems or just think about it O___O

For the second one, figure out what propels the water, etc.