1. Compound Bow
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2. CONTENTS Simple Machine EXIT How it Works Forces Acting on the Bow
Energy Transformation
How to Improve the Compound Bow
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3. Pulleys
A pulley, or cam, is located at each end of the bow. The cam is usually oblong in shape and instead of having a pivot point in the center, it is located slightly off to the side, which is what allows for “let off”. Let off is the decrease in the amount of force needed to hold the string back that occurs after the string is pulled back all the way.
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4. How it Works
As the string is drawn the cam turns and imparts force to compress the limbs. Once the cam turns all the way around, the least amount of force needs to be applied to the string to keep the limbs bent. This is known as “let off”.
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5. Forces That Act on a Compound Bow
Gravity
Elastic Force (Limbs)
Normal Force
Friction (Wind resistance and moving parts)
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6. Energy Transformations
1.Potential (Before you pull the draw string)
2.Kinetic (As you are pulling back the draw string)
3.Potential (As you hold the draw string back)
4.Elastic (When you let go of the draw string and the limbs snap forward to force the arrow forward)
5.Kinetic (The arrow moving forward)
Potential > Kinetic > Potential > Elastic > Kinetic
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7. Ways to Improve the Compound Bow
Nock of arrow
I could improve the compound bow by making the draw string magnetic and making magnetic nocks for the arrows so that it is easier to put the arrows on the string. This would allow more time aiming and shooting then putting the arrow on the string. The arrow would slip less as well prior to shooting.
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