Kinetic Energy- What It Is, Why It's Important, & How To Calculate It.

Today we're talking about kinetic energy and specifically the kinetic energy of your arrow and how that pertains to bowhunting. Now there's a lot of talk about kinetic energy out there and there's a lot of debate about how much kinetic energy do you need to shoot certain animals or certain broadheads. You know, when it comes to bowhunting, the more kinetic energy you can have, the better. And kinetic energy ultimately is explained as the amount of energy that an arrow possesses when it goes from zero to however fast that arrow is traveling, right? The more energy that that arrow has into it, obviously the better it's going to penetrate the animal when it eventually hits it. Now, when you look at kinetic energy, it is a direct correlation of the mass of the arrow, which is how much it weighs, and the velocity of the arrow, which is how fast it's flying. So the heavier arrow we have and the faster it's going, the more kinetic energy that we have. So when it comes to bowhunting, you know, there's a lot of different schools of thought out there. What's more important, a heavier arrow or a faster arrow? The current trend is certainly towards heavier arrows. I think bowhunters have come to realize that a heavier arrow has a lot of advantages to it. Number one, it's going to quiet your bow down considerably because it's absorbing more of the energy from the shot. It's also going to produce more kinetic energy, have more momentum, and hopefully better penetration. It's also going to be quieter in flight than a lighter arrow. So the pursuit of speed in the bowhunting community isn't quite what it used to be. However, speed is still important because we are shooting at animals that have a tendency to move when we shoot at them. So the faster we can get that arrow there, the better. So today when we look at kinetic energy, again, we're going to be looking at two different things. How heavy is my arrow and how fast is it flying? Now, the important thing to remember is when we calculate kinetic energy, that is calculated at the time that that arrow leaves the bow. So the minute that arrow leaves the string, it is traveling at a certain velocity. And the farther out there it gets, the slower that arrow goes. So your kinetic energy is dissipating almost immediately after you shoot your arrow. So it's not exactly the most precise calculation of how well it's going to penetrate once it hits the target, because that's a factor of how far away that target is and how heavy the arrow is. But it is a good general guideline for, can I be shooting a really big expandable broadhead with this arrow combination based on my kinetic energy? So when we look at the particular arrow that I've got here, you're going to need to know two things, of course, to calculate your kinetic energy. You're going to need to know how much this arrow weighs. And for that, we have an arrow scale. These are relatively expensive. You can get them at just about any pro shop. Of course, you can hop onto Lancaster Archery's website. You can buy them there. So you're going to buy a scale that measures in grains. A lot of your arrow scales come with this little holder here, which is pretty handy when you're measuring arrow weight. So we're going to go ahead and we're going to zero this out. We're going to put this arrow on here. And this arrow weighs 492 grains is the rating that I'm getting right now. So I've got a 492 grain arrow. The next piece of information that I'm going to need to calculate my kinetic energy is how fast is my arrow going? Obviously, how fast your arrow travels is a factor of obviously the speed, I'm sorry, the weight of the arrow, but it's also a factor of your bow. Different bows shoot different speeds and produce different amounts of energy. The amount of energy produced by this bow has got a variety of different factors into it. The most common factors that we can control as bow hunters and archers is going to be how long our draw length is. The longer the draw length you have, generally speaking, the more energy you can create, right? Because you've got a longer power stroke. You've got more force behind that arrow before it leaves the string. So draw length is a factor of how much energy you can create. And of course, draw weight. The more draw weight that you pull, the more energy you can create. Now in the bow hunting world, for most hunting situations for adults out there hunting, somewhere between 60 and 70 pounds is really all you need to go kill just about any animal in North America. You don't need to be shooting 75 or 80 or 85 pounds. There's plenty of guys out there that can do that and want to do that and enjoy doing that. And by all means, have at it. But I think it's more important for people to focus on their accuracy, their repeatability, and just making sure that they make clean shots and not worried about, you know, having to muscle back a bow that's 80 pounds because you're trying to pick up a little bit of extra speed. So that's just one thing to keep in mind. For me personally, this is my hunting bow. It's set at about 68 pounds right now and I shoot a 29 inch draw, which is probably fairly average, you know, for most adult males that are out in a bow hunting situation. So with this particular arrow and this particular bow, you would need a chronograph to shoot your arrow through a chronograph, see how fast it's going. For my setup, I'm shooting at about 283, 284 feet per second is what I'm getting out of this particular setup with this heavier arrow. Now that you have those two pieces of information, you can go to bowhunting.com, do a search for kinetic energy calculator and type in the weight of your arrow in grains and the speed of your arrow in feet per second. And it'll kick back a number telling you what the kinetic energy of your arrow is when your bow is shot. Now I've already done the calculations on this particular arrow. Again, it's a 490 grain arrow. I shoot it at about 280 feet per second, give or take. So I'm getting about 87 foot pounds of kinetic energy out of this particular setup. Now, if you go back years and years to the guides on kinetic energy and what you need to ethically go bow hunting, a lot of them used to list, you know, smaller game animals. And these animals I know aren't small, but in perspective, like antelope, deer, those size animals, they used to say 25 to 40 foot pounds of kinetic energy is what you need to bow hunt for those animals. And I think that's still an accurate guide, right? If you're a smaller stature bow hunter, if you're a woman, if you're a child, somebody that can't pull, you know, 70 pounds and shoot a 500 grain arrow, maybe you've got a 25 inch draw length and you can only pull 40 pounds. 25 to 40 pounds of kinetic energy is really all you need to kill a white tail. Obviously you should be shooting a fixed blade broadhead at that point. But as we get into some of these bigger animals, we start looking at bear, we start looking at elk, maybe moving up into moose, or if you're gonna go on maybe a dangerous game hunt, you want the most kinetic energy possible. So 87 foot pounds of kinetic energy is a ton of kinetic energy for white tail hunting, which I honestly don't know that there is a point of overkill when it comes to having kinetic energy. You just never know what's gonna happen when you release that arrow. And if you can get a good heavy arrow that's flying great for you and is still producing pretty good speeds, that's the most important thing. So again, 87 foot pounds out of this particular arrow, I would be more than happy to shoot this with any mechanical or any fixed blade broadhead. The lower or the less kinetic energy you have, you do wanna start steering towards those fixed blade broadheads because there's no question that a mechanical broadhead does absorb a lot of energy when it needs to open up when it hits a game animal. So if your arrow only has so much energy and it doesn't have a lot to spare, you really wanna steer away from those mechanical heads in terms of just getting better penetration. A fixed blade head in most cases is going to out-penetrate a mechanical head at lower amounts of kinetic energy, lower weights and slower speeds. So that is what kinetic energy is. That is how you calculate it. Again, it is nothing more than a factor of how heavy is this arrow and how fast is it going. And what they will tell you and what the numbers show is that if you want to increase your kinetic energy, the best thing to do is increase the weight of your arrow. Increasing the weight of your arrow will increase your kinetic energy faster than increasing the speed of your arrow. So the weight is more important than the speed in this particular calculation when we talk about kinetic energy. Now, a lot of people I'm sure are going to bring up arrow momentum and say that momentum is the best factor for determining penetration when you get to a game animal. And they're absolutely correct, but kinetic energy is a good starting point. It's an easy to calculate number that is going to give you a pretty accurate representation because as your kinetic energy goes up, your momentum tends to go up as well. So they kind of correlate to one another. When it comes to momentum, the best way to think about it is how difficult is this arrow to stop once it hits the target. The heavier the arrow, the more difficult it is to stop. A lot of people like to use the analogy of somebody throwing a nail at you versus throwing a railroad spike at you. That railroad spike is a lot heavier and it might be moving a little bit slower, but it's probably going to be more difficult to stop and do more damage than an actual nail is going to be. So that's a good analogy if you want to think about heavyweight arrows versus lighter arrows. So that is kinetic energy in a nutshell. If you guys have any questions, comments, concerns, feel free to leave them below and our team will do our best to get back to you as soon as possible. Make sure you check out the rest of the Bowhunt 101 videos in this playlist and make sure you check out bowhunting.com. Our entire Bowhunt 101 section has a lot of great information about archery and bowhunting. Whether you are a beginner or a seasoned veteran, there's a lot of great information right there for you.