How to calculate the energy of a slingshot projectile?

Question

This answer made me wonder how a slingshot would compare in power to an airgun, especially as for that location, without a license you are limited to 12 ft-lbs of energy. For hunting with firearms, more energy means that you are more likely to get a clean kill, and a minimum level is often mandated by law in the United States for hunting a species.

I looked for data, but there really isn't much especially as compared to airguns and it probably depends on the person.

How would one calculate the energy of a slingshot projectile?

Answer 1

In order to do this, you need the weight of the projectile and its velocity. The way to measure the velocity is to use a modern gun chronograph, you shoot the projectile through the to screens and it will measure the velocity for you.

Then you take the weight of the projectile and plug it into the equation,

(weight in grains * velocity in feet per second squared)/450240 

Equation Source

or you could plug the numbers into an online calculator like any of these

• Airgun Calculators
• Foot lbs of energy
• Bullet kinetic energy calculator

and get the result.

Ft-lbs of energy aren't everything when it comes to getting clean kills but as a comparison between one projectile and another, it's probably the easiest to do.