SpudFiles

A basic slingshot question

Question:

Assume that prior to drawing back the pouch, it is 10" from the fork.

You pull it back 20" to 30" from the fork.

Would the speed of the projectile be the same if it is released from the pouch at 10" as it would if it was released after it passed the fork?

BoyntonStu

You have to figure in friction of moving through dead air, the rate of acceleration to the point where the acceleration stops and the dead air really starts affecting the "ball bearing" for reference. Off the top of my head...

Unless I'm being an idiot, for practical purposes, the two are essentially the same.

Ragnarok wrote:Unless I'm being an idiot, for practical purposes, the two are essentially the same.

Explain please, witch two?

I would say that the release 10" before the fork would be prefered. This assumes the drag on the cables and pouch is greater than the drag on the projectile. Both the cable/pouch and the projectile start to decelerate at the 10" mark (the equilibrium lenght of the slingshot). The cable/pouch probably has a higher Cd and lower sectional density than the ammo so it will decelerate faster than the ammo. If the ammo is still connected to the pouch then the pouch will decelerate the ammo more than the ammo decelerates itself.

boyntonstu wrote:Would the speed of the projectile be the same if it is released from the pouch at 10" as it would if it was released after it passed the fork?

It will be FASTER at the 10" mark than it will be after it passes the fork. Not much faster, but faster. Why? Because once the rubber makes it to it's unstretched length (the 10" mark), you've accelerated the projectile as much as you're going to. After that, it's decelerating all the way.

And truthfully, it will probably be at it's fastest ever so slightly before the 10" mark. For at the 10" mark the acceleration force from the rubber is zero while drag is non-zero. Peak velocity will be just before that... At the last moment when acceleration force due to the rubber exceeds drag forces.