1. Chapter 5 :
Simple Machines: devices with few moving parts that make work easier. They can:
Change direction of applied force or
Change size of applied force or
Change distance thru which force works.

2. Why Use Simple Machines?
For the mechanical advantage…
Makes something easier to do, but it takes a little longer to do it
For example, going up a longer flight of stairs instead of going straight up a ladder

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

4. Definitions: Energy: Force: Ability to do work A Push or a Pull
Work: Force (N) x Distance (m)
if there is not a change in position, then no work is done
So w = f d, f = w / d and d = w / f
Work is measured in joules (J) or kilojoules (kJ)

5. Work input & output have to equal
Work input is the amount of work done on a machine.
Input force x input distance
Work output is the amount of work done by a machine.
Output force x output distance
15 m
Wout = Win
Fout x Dout = Fin x Din
10N x 3m = 2N x 15m
Din
Dout
3 m
Fin
10 N

6. Input-Output Locations
Input is where the effort force is applied
Output is where the load is lifted or moved
Mechanical advantage: # of times a machine multiplies your effort force. Use this formula:
Mechanical advantage = resistance force / effort force OR
MA = Fr / Fe

7. Levers A simple machine made of a bar that turns around a fixed point.
Makes lifting weight easier by redirecting force over a different distance or changes direction of the force.

8. Parts of a Lever Fulcrum: fixed point
Effort force, Fe: force applied by user
Resistance force, Fr: force applied by object to be moved.
Resistance (or load): is object to be moved.

9. First Class Lever
Fulcrum is between Ef (effort) and Rf (load). Effort moves farther than Resistance. Multiplies Ef and changes its direction. Examples: claw end of hammer, seesaw, crowbar, scissors, pliers, your neck (cervical vertebrae)

10. Second Class Lever Rf (load) is between fulcrum and EF
Effort moves farther than Resistance. Multiplies Ef, but does not change its direction
Examples: nut crackers, wheel barrows, doors, and
bottle openers. Also standing on your toes.

11. Third Class
Lever
Ef is between fulcrum and Rf (load) Resistance moves farther than Effort. Does not multiply force. Multiplies distance the effort force travels. Examples: tweezers, arm hammers, & shovels. Holding a weight in your hand with arm extended.

12. Levers in the Body

13. Pulley Pulley are wheels and axles with a groove around the outside
Makes lifting things easier by redirecting force
A pulley needs a rope, chain or belt around the groove to make it do work

14. Pulleys
Examples: flag pole, elevator, sails, fishing nets, clothes lines, cranes, window shades and blinds, rock climbing gear

15. Diagrams of Pulleys Fixed pulley: Movable Pulley:
A fixed pulley changes direction of force; does not increase F or create MA (so MA = 1).
MA of a moveable pulley = the number of ropes that support the moveable pulley.
Movable Pulley:

16. 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. 

17. Inclined Planes
An inclined plane is a flat surface that is higher on one end
Inclined planes make the work of moving things up easier, but it increases distance
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. 

18. Inclined Plane
Egyptians used simple machines to build pyramids. A long incline made of dirt rose upward to the pyramid top gently. Blocks of stone were placed on large logs (another simple machine - wheel & axle) & pushed slowly up the inclined plane to the top of the pyramid.

19. Inclined Plane - Mechanical Advantage
Mechanical advantage of an inclined plane =
length of the slope
height
While plane gives MA, it does so by increasing the distance thru which the force must move.

20. Screw Turns rotation into lengthwise movement
Takes many twists to go a short distance
Holds things together
Mechanical advantage of an screw is calculated by dividing the circumference by the pitch of the screw.
The tighter the turns of the plane – the greater the MA.

21. Screw
Examples: screws, bolts, clamps, jar lids, car jack, spinning stools, spiral staircases

22. Wedges Two inclined planes joined back to back.
Wedges are used to split things, push them

23. Wedge – Mechanical Advantage
The mechanical advantage of a wedge can be found by dividing the length of either slope (S) by the thickness (T) of the big end. S
The thinner the wedge, the higher the MA of the wedge. T

24. Wedge
Examples: axe, doorstop, chisel, nail, saw, jackhammer, bulldozer, snow plow, horse plow, zipper, airplane wing, knife, bow of a boat or ship

25. WHEEL & AXLE
Makes it easy to move things by rolling and reducing friction
Examples: car, bicycle, office chair, fan shopping cart, hand truck, roller skates

26. WHEEL & 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.

27. Wheel & Axle
The mechanical advantage of a wheel and axle is the ratio of the radius of the wheel to the radius of the axle.
In the wheel & axle above, radius of the wheel is 5x larger than the radius of the axle. Therefore, MA is 5:1 or 5.
The wheel & axle also increases speed by applying input force to the axle rather than to a wheel.
The bigger the wheel is compared to the axle width, the greater the MA. 5 1

28. GEARS-Wheel and Axle
Each gear in a series reverses the direction of rotation of the previous gear. The smaller gear will always turn faster than the larger gear.

29. Complex Machines
Combining two or more simple machines to work together
Examples:
Car jack combines wedge and screw
Crane or tow truck combines lever and pulley
Wheel barrow combines wheel and axle with a lever

30. Rube Goldberg Machines
Rube Goldberg machines are examples of complex machines.
All complex machines are made up of combinations of simple machines.
Rube Goldberg machines are usually a complicated combination of simple machines.
By studying the components of Rube Goldberg machines, we learn more about simple machines

31. Safety Device for Walking on Icy Pavements
When you slip on ice, your foot kicks paddle (A),
lowering finger (B), snapping turtle (C) extends neck
to bite finger, opening ice tongs (D) and dropping pillow (E),
thus allowing you to fall on something soft.

32. Rube Goldberg Machine Examples https://www. youtube. com/watch
Resources