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# 2009 Pulleys

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### 2009 Pulleys

1. 1. <ul><li>Notes: Pulleys, wheel and axles and gears </li></ul><ul><li>H: Review Notes </li></ul>
2. 2. Pulleys, Wheel and axle and Gears April 20, 2009
3. 3. Objectives <ul><li>Define pulley, wheel and axle, and gear </li></ul><ul><li>Compare fixed, movable and compound pulleys </li></ul><ul><li>Calculate the MA of pulleys and a wheel and axle </li></ul>
4. 4. Pulleys <ul><li>A pulley is a rope, belt or chain wrapped around a grooved wheel. </li></ul><ul><li>Pulleys are modified forms of a first class lever. </li></ul>
5. 5. MA of a Pulley <ul><li>MA = number of lines supporting the load </li></ul>MA = 2 Two lines are supporting the load. MA = 1 One line is supporting the load.
6. 6. <ul><li>Types of Pulleys </li></ul>Fixed compound moveable
7. 7. Fixed Pulleys <ul><li>A fixed pulley is a pulley that is attached to something that does not move. </li></ul>
8. 8. <ul><li>Fixed pulleys change the direction of the force in a rope (called a belt when it goes in a full circle) but not the size of the force. </li></ul>mechanical advantage of 1
9. 9. Moveable Pulley The load is supported by 2 rope arms under the pulley . You must pull 2 times the distance to lift the load.
10. 10. The effort arm will always be twice the length of the resistance arm so the mechanical advantage of a single moveable pulley is 2.
11. 11. Compound Pulley <ul><li>Two (or more) pulleys can be arranged to work together </li></ul>Allows the user to gain both Mechanical and Directional Advantage. The more rope arms supporting the load the greater the Mechanical Advantage.
12. 13. Block and tackle <ul><li>A compound pulley where several pulleys are mounted on each axle, further increasing the mechanical advantage. </li></ul>
13. 15. The Wheel and Axle <ul><li>Two or more wheels are connected by an axle. </li></ul><ul><li>The wheel turns with or around the axle. </li></ul>
14. 16. Wheel & Axle M.A. <ul><li>M.A. = Wheel Circumference </li></ul><ul><li>Axle Circumference </li></ul>Example: 10 in = 5 2 in
15. 17. Gears <ul><li>A gear is a wheel with teeth that fit in between each other and turn. </li></ul>