Mount a lawn mower on a fixed stand. Position high speed camera to see spinning blade. Using grass/sod on a movable platform, such as a sheet of plywood (with wheels or rollers), pull the grass through the lawn mower blade

Also would like to see what happen when you hit a rock. if you hit the right kind of rock, and if the brush you cut is dry enough.... can you get a spark and catch on fire?

if somehow you could mount a camera on the lawnmower looking down into it, i think it would be a really cool view. maybe run the lawnmower over some fruit, piece of meat, and a few other random objects for entertainment value

It's getting down to the level of the grass as the blades slice them in half that's the tricky bit.

I've tried it with my Casio Ex-F1 and, if my mower had glass/transparent casing, then I could do this from the side:

http://www.youtube.com/watch?v=wUMAoXEk5-w

The camera's not good enough to zoom in though.

what happens when hitting sticks.

Can the blades be redesigned to improve cutting and reduce hazards