Question

How might the longbow and gunpowder technology have changed what weapons were used on medieval battlefields?

Answer 1

 Well the longbow, made the classic attack of sword, lance or joust useless, for the most part.
When someone could kill a soldier from a hundred yards, there was no need to get close enough for horse or foot soldier to fight
. 
Gunpowder brought in the canon, and this was a weapon that was effective even farther than the long bow.
It could kill multiple people at long range, plus, it made the stone castle obsolete, because canon balls could blast them apart.