Spring Projectile Launcher Help

canada123

I need to build a device that launches a small bouncy ball anywhere from 1-4m using a spring. The spring is initially compressed as much as it can be, so this device would need to work by stretching the spring somehow. I have tried to think of a few ways to do this, but have not come up with any good ideas. Do you guys have any idea how to build one? Thanks in advance for any help.

Simon Bridge

Hint - look at a slingshot: two springs, initially compressed, get stretched and released.
What are your constraints - have you been given the spring or do you get to pick one?