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Levers and Pulleys LOL’s

Levers and Pulleys LOL’s. Introduction to Levers. Line of Learning (LOL) A lever is a simple machine that is used to gain mechanical advantage, such as making work easier. A lever arm is a stick or beam that is free to pivot at a point A fulcrum is the point where the lever arm moves.

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Levers and Pulleys LOL’s

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  1. Levers and Pulleys LOL’s

  2. Introduction to Levers • Line of Learning (LOL) • A lever is a simple machine that is used to gain mechanical advantage, such as making work easier. • A lever arm is a stick or beam that is free to pivot at a point • A fulcrum is the point where the lever arm moves. • The load is the weight. • The effort is the force used to move the load. Lever Arm

  3. Introduction to levers Cont. • Line of Learning (LOL) • The unit used to measure effort is a Newton (N). • A lever can make a load easier to lift, it can move loads, and it reduces the effort needed. • In a lever system the farther from the fulcrum the effort is applied, the greater the advantage to the lever user. • When the load is closer to the fulcrum it makes the lever easier to use. L E F

  4. Lever Experiment A • Line of Learning (LOL) • Any benefit you get from using a lever, or simple machine is called advantage • Using a two-coordinate graph is a helpful visual aid to show relationships between two variables. • The farther the effort is from the fulcrum, the easier it is to lift the load. • The effort needed to lift the load decreases as the load gets closer to the fulcrum; the effort increases as the load gets farther from the fulcrum.

  5. Classes of Levers • Line of Learning (LOL) • Class-1 Lever • Example: Seesaw, crowbar, paint can opener

  6. Classes 0f levers • Line of Learning (LOL) • Class-2 Lever • Examples) Wheelbarrow, nutcracker, bottle opener

  7. Classes of Levers • Line of Learning (LOL) • Class-3 Lever • Examples) Rake, broom, hammer, human arm, tweezers

  8. A helpful trick to remember classes • F-1 • L-2 • E-3 • The letter is in the middle of the system. So if the fulcrum is in the middle than it’s a class-1 lever, if the load is in the middle it’s a class-2 lever, if the effort is in the middle it’s a class-3 lever. Remember F-L-E 1-2-3

  9. Lever Diagrams • Line of Learning (LOL) • A diagram is a drawing that describes the relationship of all the parts of a system. • A diagram uses a system of symbols and conventions to communicate information about lever designs. • Using a diagram is easier than trying to draw an accurate picture of the simple machine. Ex) a wheel barrow could be difficult to draw and show how it works. The best way to record information about a lever system is through a diagram.

  10. One Pulley Systems • Line of Learning (LOL) • A pulley is a wheel with a grooved rim in which a rope can run to change the direction of the pull (force) that lifts the load. • A fixed pulley has a wheel that is attached to something above the load. • A movable pulley has a wheel attached to the load (moves with the load)

  11. One Pulley Systems • Line of Learning (LOL) • Mechanical Advantage reduces the effort (force) needed to lift the load or overcome a resistance; it results from using a simple machine. • Directional Advantage is a change in direction that results from passing a rope through a pulley

  12. One Pulley Systems • Line of Learning (LOL) • Do single-pulley systems provide advantage? • Single-fixed pulley = directional advantage, they change the direction of effort needed • Single moveable pulley = mechanical advantage, they reduce the effort needed to lift the load

  13. Two Pulley Systems • Line of Learning (LOL) • Two pulley systems can provide a greater mechanical advantage when lifting a load that having one pulley • A simple machine is any of the six basic devices that provide mechanical or other advantage like levers and pulley • The 6 simple machines are • Screw -wheel and axle • Wedge - lever • Inclined plane - pulley

  14. Effort in Pulley Systems • Line of Learning (LOL) • The greater the number of ropes supporting the load, the less effort needed to lift the load • More ropes = less effort • The more supporting ropes you have the less work you have to do • To figure out the effort need divide the load by the number of supporting ropes

  15. Measuring the Distance • Line of Learning (LOL) • “You never get something for nothing” applies to pulleys because….. • The benefits gain (making work easier) by using simple machines are always balanced by cost. • When the benefits outweigh the cost the machine is a useful tool. • With pulleys we looked at the number or ropes compared to the distance required to travel….if you had to triple the distance the machine was not a useful tool

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