A crossbow has a process by which it shoots an arrow. It uses a string to propel its projectiles, but it also has the feel of a gun. It is the best of both worlds! Imagine a vertical archery bow that is shot horizontally with the aid of a trigger and you have a crossbow. In the early years, the crossbows had very similar parts. They were typically mounted onto a stock, which is what gave them their gun-like feel. The arrows would make their way through a groove that was on the tiller and be off towards their targets.
If you look at crossbows, you can see that they all function in similar manners. Crossbows are typically made from materials that are strong, flexible and lightweight. These materials allow it to achieve its desired kinetic energy. Kinetic energy is the energy of movement. Everything that moves has kinetic energy. Typically, when you are trying to grasp the concept of kinetic energy, you should think that the more the object weighs and the faster it goes the more energy that it will have. This fact is completely true and should be kept in mind when thinking about crossbows.
An arrows string works very similar to that of a compressed coil or a spring. When you push down on the coil (or pull back on the string), there is a certain amount of elastic potential energy that is stored with the crossbow. The way it is set up, makes it use these same energy principles. The composition of the strings allows you to pull back on the limbs and harness this energy at full draw. The tendency of the crossbow and the string are to go back to their original shape. As they are going back to their original shape, they will propel the arrow towards the target.
Two aspects will determine the power that your crossbow can yield. These aspects are known as the draw weight and the draw length. The draw weight is the amount that you have to pull back in order to draw the bowstring back. If you are using a recurve bow then the draw weight will increase the entire way back as you draw the string. If you are using a compound bow then there will be a point in which you achieve a let-off. The let off is the point in a compound bow in which you get a certain percent of weight that is let-off so that you do not have to hold the entire load. The draw length is the amount of space between when the bow is at rest and when it is at full draw. The longer the draw length is, the more powerstroke that you are going to be able to deliver. This means that the longer the draw length, the more potential for energy.
Make sure that you are following all of the correct safety procedures when you are shooting your crossbow. The physics behind how crossbows shoot show you that they are not child's play. The draw length and draw weight combinations that some of the crossbows offer are meant to shoot their projectiles at speeds of upwards of 400 feet per second. 272 miles per hour is no joke. Make sure to stay safe and enjoy your hunt.