## Compound Bows and Energyby Holden

### A Small History

The first compound bow was granted in 1969 by a man named Holless Allen. It was better than the normal recurve bow because of the pulley system that reduced the strength needed to pull back the cables of the bow. Making the arrows fly faster and hit harder.

### Potential Energy and Compound Bows

You get the potential energy from the weight of the pull back and the length of the pull back. The heavier the bow and the longer lenght you can pull the cable, the more potential energy you get.

### Kinetic Energy and Compound Bow

After you pull back the bow and let go all of the potential energy turns into kinetic energy. Now there are more variables on how fast your arrow is and how hard it hits. The arrows weight, length, and shape of the arrow are all variables in your shot.

### Conversions

• Pulling back the cable uses elastic potential energy and when released it turns into kinetic energy
• The pulleys turn machenical energy into elastic potential energy

### Momentum

An arrow gains momentum after you release the cables. The elastic potential energy becomes kinetic energy and fires the arrow. The arrows wieght and how fast the cables fling the arrow determin the momentum.

### Compound Bows vs Newtons 3 Laws of Motion

Newtons first law of motion is that an object at rest will stay at rest and an object in motion will stay in motion unless it is acted on by an outside force. So when you shoot an arrow it will countinue to fly in the same direction forever until it is acted upon by an oustide force like air resistence or a target.

Newtons second law of motion is F=m x a(Force=Mass x Acceleration). When the arrow is fired from the bow its mass and the acceleration of the arrow determins the force that it will give. We get the acceleration of the arrow from the bow itself. Using its elastic potential energy to shoot the arrow.

Newtons third law of motion states for evey action there is an equal and oppisite reaction. When you let go of the cable you feel a slight jerk, thats because when you let go all of that force is shooting forward and because evey action has an equal and opposite reaction you feel a little bit of that force.

### Friction

When you set the arrow on the rest you create sliding friction. As you pull back the bow and release the arrow it slides on the rest and creats sliding friction.

### Speed/Velocity

The speed and velocty of the arrow all determins on the bow itself. The weight and draw back lenght of the bow is what makes the arrow fly. The more weight and greater draw back lenght you have, the more speed and velocity the arrow will gain.

#### Sources

http://archeryreport.com/2010/03/archery-history-compound-bow/