I did a similar thing in high school physics (43 years ago). We were photographing two balls - one dropped vertically and the second identical ball kicked out horizontally at 90 degrees. It proved that they both fell and landed at the same rate.

It took some experimentation to get the exposure right, but it can be done. Opening the lens up to f2.8 and going to 400 speed film will give you 4 more stops. That's a lot, especially if you're already getting some image, just not enough.

For what it's worth, when Harold Edgerton was pioneering how to do this at MIT; he, too, had to make test exposures and process individual sheets of film before dialing it in.