A 0.5kg apple is placed at the edge of a table, 0.8m above the floor. A 10g bullet is shot at the apple in a direction perpendicular to the table's edge. As the bullet passes through the apple, its speed decreases from 600 to 480m/s. The apple falles off the table.
a) Find the apple's speed immediately after the collision.
b) How far away in a horizontal direction is the apple going to hit the floor?

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If the bullet is travelling perpendicular to the table's edge, in many cases the apple will stay on the table.

The question is poorly worded - who knows what "in a direction perpendicular to the table's edge" means? That doesn't tell you at what angle the bullet was fired relative to the table surface. For example, it could be that the bullet is fired straight down into the top of the apple from above, in which case the apple won't move. However, I think what the question meant to say was "in a direction horizontal to the table and perpendicular to the table's edge." If that's the case, and given that the bullet slows as it proceeds through the apple (i.e, some momentum is transferred to the apple) and the apple is positioned right at the edge of the table, the apple will indeed fall off the table.