How does the weight of a person affect his jumping distance on a bike?

Answer 1

If you're talking about jumping off a cliff, speaking from a physics standpoint, all objects fall at the same rate.

The distance you jump is only affected by how much speed you have when you leave the cliff. There are other small factors to take into account, but generally weight won't affect jumping distance.

Answer 2

As all tandem riders will know, the heaviest bicycle will descend the quickest. (roughly the same wind resistance,more momentum.)

Assuming there is a downhill run, the increased in speed should result in a longer jump. (if technique is ok).

If there is a flat run up (or uphill), a heavier rider will have to burn more energy to get up to speed so will jump shorter.

Weight downhill good
Uphill or flat bad