1. Simple Machines and Mechanical Advantage

2. Simple Machines
Ancient people invented simple machines that would help them overcome resistive forces and allow them to do the desired work against those forces.

3. Simple Machines The six simple machines are: Lever Wheel and Axle
Pulley
Inclined Plane
Wedge
Screw

4. Simple Machines
A machine is a device that helps make work easier to perform by accomplishing one or more of the following functions:
transferring a force from one place to another,
changing the direction of a force,
increasing the magnitude of a force, or
increasing the distance or speed of a force.

5. Mechanical Advantage
It is useful to think about a machine in terms of the input force (the force you apply) and the output force (force which is applied to the task).
When a machine takes a small input force and increases the magnitude of the output force, a mechanical advantage has been produced.

6. Mechanical Advantage MA = output/input
Mechanical advantage is the ratio of output force divided by input force. If the output force is bigger than the input force, a machine has a mechanical advantage greater than one.
If a machine increases an input force of 10 pounds to an output force of 100 pounds, the machine has a mechanical advantage (MA) of 10.
In machines that increase distance instead of force, the MA is the ratio of the output distance and input distance.
MA = output/input

7. No machine can increase both the magnitude and the distance of a force at the same time.

8. The 6 Simple Machines Screw Wedge Inclined Plane Pulley Wheel and Axle
Lever

9. Inclined Plane

10. Inclined Plane
The Egyptians used simple machines to build the pyramids. One method was to build a very long incline out of dirt that rose upward to the top of the pyramid very gently. The blocks of stone were placed on large logs (another type of simple machine - the wheel and axle) and pushed slowly up the long, gentle inclined plane to the top of the pyramid.

11. Inclined Planes
An inclined plane is a flat surface that is higher on one end
Inclined planes make the work of moving things easier
A sloping surface, such as a ramp. An inclined plane can be used to alter the effort and distance involved in doing work, such as lifting loads. The trade-off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed. You can use this machine to move an object to a lower or higher place.  Inclined planes make the work of moving things easier.  You would need less energy and force to move objects with an inclined plane.  11 11

12. The Lever
A lever is a rigid bar that rotates around a fixed point called the fulcrum.
The bar may be either straight or curved.
In use, a lever has both an effort (or applied) force and a load (resistant force).

13. There are 3 Classes of Levers
Depends on the location of 3 items:
1. Fulcrum – fixed point on a lever
2. Effort Arm – the part of the lever that exerts the effort force.
3. Resistance Arm – the part of the lever that exerts the resistance force.
 EA 
RA

14. 1st Class Lever Changes the direction of the force
Multiplies effort force
Magnifies speed and distance
Ex: seesaw, crowbar, scissors

15. 2nd Class Lever Multiply effort force
Mechanical advantage is always greater than 1.
Ex: bottle opener, boat oars, wheel barrow

16. 3rd Class Lever Magnifies speed and distance
Mechanical Advantage always less than 1
Ex: baseball bat, golf club, broom, shovel

17. WHEEL AND AXLE
The axle is stuck rigidly to a large wheel. Fan blades are attached to the wheel. When the axel turns, the fan blades spin.

18. Pulleys Pulley are wheels and axles with a groove around the outside
A pulley needs a rope, chain or belt around the groove to make it do work

19. Diagrams of Pulleys Fixed pulley: Movable Pulley:
A fixed pulley changes the direction of a force; however, it does not create a mechanical advantage.
Movable Pulley:
The mechanical advantage of a moveable pulley is equal to the number of ropes that support the moveable pulley.

20. COMBINED PULLEY
The effort needed to lift the load is less than half the weight of the load.
The main disadvantage is it travels a very long distance. 

21. Mechanical Advantage
The Mechanical Advantage is calculated by dividing the Output Force by the Input Force. This is used for ANY simple machine. After the trials for 1-6 strings have been completed it is time to look at the results obtained. It becomes clear that the more strings used to support the load, the force needed to lift the load decreases. We call this an Inverse Relationship. The relationship between the mechanical advantage and the # of strings supporting the load may become much clearer at this point. 21