How much does velocity factor into energy

[Ruger M77]

I was wondering if anybody knows how much velocity factors into energy when it comes to  shot. Like with a rifle you load a 180gr boat tail  in a 30-06 at 2700 fps and get 2900 foot pounds of energy. then you can push the same bullet to 3,000 fps out of a 300 win mag and end up with 3,600 foot pounds. Now lets say we have two #6 pellets one is going 1,300 and the other is going 1,100 how much harder will the faster pellet hit? Maybe this is a dumb question but I'm just curios.

[Skeeterbait]

Kinetic energy is the energy of motion. An object that has motion - whether it is vertical or horizontal motion - has kinetic energy. There are many forms of kinetic energy - vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another). To keep matters simple, we will focus upon translational kinetic energy. The amount of translational kinetic energy (from here on, the phrase kinetic energy will refer to translational kinetic energy) that an object has depends upon two variables: the mass (m) of the object and the speed (v) of the object. The following equation is used to represent the kinetic energy (KE) of an object.

KE = 1/2 * m * v2

where m = mass of object

v = speed of object

This equation reveals that the kinetic energy of an object is directly proportional to the square of its speed. That means that for a twofold increase in speed, the kinetic energy will increase by a factor of four. For a threefold increase in speed, the kinetic energy will increase by a factor of nine. And for a fourfold increase in speed, the kinetic energy will increase by a factor of sixteen. 


http://www.physicsclassroom.com/class/energy/u5l1c.cfm



So in the case you give where you know the starting kinetic energy is 2900 ft/lbs and the velocity is 2700 f/sec, increasing the velocity to 3000 f/sec can be figured as

3000/2700 = 1.1111111111 or in other words 3000 is a 1.1111111111 factor of 2700

kenetic energy will increase by the square of this factor

1.1111111111 * 1.1111111111 = 1.2345679012 so kenetic energy will increase by the factor of 1.2345679012

2900 * 1.2345679012 = 3580 ft.lbs   or 3600 to make it easy to remember.


It will be easy to compute the resulting kenetic energy of the pellet with the increased speed if you know the kenetic energy of the pellet at the original speed.  Or you can use the formula to compute the kenetic energy of the pellet directly if you know the mass of the pellet in grams and the speed in meters/sec.  A lot of conversions have to be completed to accomplish this though.

[BandedSpur]

I agree with all that Skeeterbait posted. Increased velocity has a strong positive effect on KE. But what we have to remember is that the only velocity that matters is velocity of the pellet at impact, not what it was when it left the muzzle. Unfortunately the faster a pellet leaves the muzzle, the faster it is slowed by air resistance, so that most of the increase in velocity at the muzzle is lost at the target.

For example, the 200 fps advantage of a lead 6 at a MV of 1300 vs another at 1100 is down to just 61 fps @ 40 yds. The faster pellet will strike with 2.1 ft-lbs of energy while the slower will strike with 1.75 ft-lbs.

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I love this discussion but my eyes are starting to glaze over. What role does density play in how hard that pellet hits? Like Tungesten versus lead?

[Skeeterbait]

Kenetic energy will increase by a direct proportion to the proportional increase in mass, unlike velocity which is the square of the proportional increase in velocity.

Mass generally increases with increase in density, but then we get into terminal ballistics where the difference of hard shot that is more likely to pass thru and waste some of its energy vs soft shot that may remain in the animal and expend all their energy.  That simply cannot be figured by a formula. 

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That is some more good information and it seems logical to me. No more questions from me tonight, professor. Thanks and good night. Got to go scout tomorrow morning!

[Ruger M77]

Hey thanks for the info your a heck of a lot smarter than me

[mightyjoeyoung]

Think of it this way.  If you double the weight you DOUBLE the K.E.  If you double the velocity, you QUADRUPLE the K.E..


Take an object that weighs say 500 grains to 1,000 grains at a given velocity of say 2,000 fps, you DOUBLE that object's K.E.. (from 4,464.29 FPE to 8,928.57 FPE)

If you double the velocity of that same 500 grain object from 2,000 fps to 4,000you QUADRUPLE the K.E..  (from 4,464.29 FPE to 17,857.14 FPE). 

[jfair]

Kenetic energy will increase by a direct proportion to the proportional increase in mass, unlike velocity which is the square of the proportional increase in velocity.

Mass generally increases with increase in density, but then we get into terminal ballistics where the difference of hard shot that is more likely to pass thru and waste some of its energy vs soft shot that may remain in the animal and expend all their energy.  That simply cannot be figured by a formula.

Great job. This is hard to explain in the typed word because there are so many variables to consider. You did very well with both posts. Thanks

Bullets are a totally different animal from pellets when considering what they are intended to do. A lead  bullet is designed to expand and transfer it's kinetic energy into the animal. Best case scenario is when the bullet passes through completely and falls to the ground on the far side of its target. All energy is transferred.

Copper plated lead pellets more often than not retain their original shape when contacting a turkey. They simply are not designed to expand or deform.