How to Design a Delayed Spring Mechanism for a Physics Project?

[supaSPED]

Homework Statement

So pretty much, the goal of the project is to create a car which has a launcher on it (elastic powered). The car starts at one zone, rolls 4m forward (for maximum marks, it has to hit 4m on the mark), then fires at the perpendicular angle from its initial direction at a dartboard type target. (This is all on the floor)

That target is a circle, in which the center is 4m away from the cart pathway. The circle itself has 4 zones (bullseye, and every zone after that, bullseye gets the highest marks).

So, the problem that i have is that we need to make a spring which is delayed. Once we let the car travel, we are no longer allowed to touch it. We also have to let the car reach its ideal zone 4m away before we can launch the object (for marks).

Not only that though, the spring shouldn't be launched while the cart is moving because that will make it innacurate. Having it launch AFTER the cart stops moving is ideal.

So due to these reasons, i need to build a spring which is delayed. As in I can set it to launch, maybe like, a minute after its initial set up.

no motors can be used. teacher wants elastic energy.

The Attempt at a Solution

So i have a pretty good idea for the car itself, just have it spring loaded to shoot for the 4m. The problem is the delayed spring. Making a spring launcher is easy, but to have it so that it is delayed is hard. I need help

 

[Valkarie]

with how to make it so that it is delayed, or any alternatives that i can use. What I was thinking of was to have a timer somehow connected to the spring. This way when the timer hit 0, the spring would launch. However, I am not sure how this would work, and I am completely stumped on where to even start. Any help would be appreciated.