1. LEVERS by David Sagae 8th grade

2. LEVERS Definition: A lever is any rigid rod or plank that pivots, or rotates, about a point. The point about the lever that pivots is called fulcrum.

3. 3 TYPES OF LEVER First Class Lever Third Class Lever Second Class Lever

4. FIRST CLASS LEVER The fulcrum lies between the effort and the load. The point on which the bar is resting is the fulcrum. The bar is the lever. The power or effort alone would not move the weight.

5. FIRST CLASS LEVER Types Type A: The Fulcrum is exactly in the middle. e.g:. teeter totter Type B: The fulcrum is closer to the load force. e.g.: crowbar Type C: The fulcrum us closer to the effort force. e.g.: rowboat car

6. FIRST CLASS LEVER examples Axis is placed between force and resistance Lever characteristics -Balanced movement: Axis is midway between force and resistance eg.: seesaw -Speed and range of motion: axis is close to force eg. elbow extension -Force : axis is close to resistance ForceAxisResistance

7. SECOND CLASS LEVER Lifting a heavy log by means of a lever which has been pushed under the log. Note that the fulcrum is the point where the lever touches the ground, and the load is between the fulcrum and the point where the effort is exerted. The effort is exerted upwards.

8. SECOND CLASS LEVER examples ForceResistanceAxis Resistance is between axis and force Lever characteristics -Produces force: Large resistance can be moved by relatively small force -Weight machines: More resistance needed, lower inertia, smoother feel.

9. THIRD CLASS LEVER Imagine soil being lifted from a pile on the ground into the back of a truck with a shovel. The load is located at the end of the lever. The effort is exerted between the load and the fulcrum.

10. THIRD CLASS LEVER examples ForceResistanceAxis Force is placed between the axis and resistance Lever characteristics -Produces speed and range of motion -Requires relatively great force to move even small resistances -Weight machines: Less resistance needed, greater inertia, harder to start/stop movement.

11. MECHANICAL ADVANTAGE MA = Factor by which a mechanism multiplies the force/torque applied to it. MA = output force or displacement of load = effort arm input force displacement of effort resistance

12. MECHANICAL ADVANTAGE Comparison using formula A construction worker uses a board and log as a lever to lift a heavy rock. Calculate the specific Mechanical Advantage of the lever: #Input ArmOutput ArmMechanical Advantage 13 feet1 ft3 23 feet2 ft1.5 33 feet3 ft1 43 feet4 ft0.75 53 feet5 ft0.6 64 feet1 ft4 75 feet1 ft5 86 feet1 ft6 97 feet1 ft7 108 feet1 ft8 Conclusion: As the input arm (effort arm) increases, the mechanical advantage increases. As the output arm (resistance arm) increases, the MA decreases. MA = INPUT ARM / OUTPUT ARM