Does a sling or a gun exert more initial force of the projectile?

Allenph

First of all this is probably the only time I will be on this forum.

At first this seems a no brainer. But I am a weekend survivalist and I made a sling that can sling rock a little more then 1" in diameter 120 yards at an angle of about 50-55 degrees. After some research the type of rock I am flinging is limestone which means it weighs about 2 ounces. Lets use say, a .22 caliber bullet. The bullet would weigh a little less then .09 ounces and go around 175 yards at 90 degrees. I have NO idea how to figure this out and am curious to know the answer. So does it take more force to shoot the rock or shoot a bullet?

Nessdude14

It's kind of important to know an accurate weight for the rock you used if you want to calculate the impulse required to accelerate it. Looking up the weight of a similar small rock won't do.

Instead, let's find some figures from the internet to use. The muzzle energy of an average .22 LR pistol is about 160 Joules, according to the wikipedia entry below. This means that the bullet leaves the muzzle of the gun with 160 Joules of kinetic energy.
http://en.wikipedia.org/wiki/Muzzle_energy

In the following video, they claim that the world record kinetic energy for a handheld slingshot projectile is 113 Joules. This is less energy than a .22 bullet, and chances are you're firing them off with quite a bit less energy than the world record holder.
http://youtu.be/1v4TEX2erog

So, in short, a projectile from a handgun has more kinetic energy (and requires a greater impulse) than a projectile from a handheld slingshot.

Allenph

Excellent thanks for answering my question

Allenph

I learned the math. My stone has 51 joules and a .22 CB round has 10% less at 45 Joules.

jbriggs444

More kinetic energy, yes. More impulse -- I don't think so.

The kinetic energy of a projectile scales as the square of its speed. The momentum of a projectile scales linearly with its speed. That means that a fast-travelling .22 slug has lots of kinetic energy but relatively little momentum compared to a slow-travelling sling stone.

"Impulse" is a measure of momentum, not energy.