1. Machines
Making Work Easier

2. Machines A device that makes work easier Can you think of some?
Some powered by engines/motors, others powered by people
Can you think of some?
SIMPLE MACHINE = a device that does work with only one movement
I have some examples…
There are 6 types
Door knob
Bottle cap
Ramp
Hammer
Crowbar

3. Advantages of Machines
They make work easier by…
Multiplying the effort force
Changing the direction of the applied force you exert
Increasing the distance through which the resistance force moves
Overcoming gravity and friction

4. Applying force and doing work
EFFORT FORCE = the force applied to a machine
RESISTANCE FORCE = the force applied by the machine to overcome resistance

5. Where is the effort force? Where is the resistance force?
For Review………………
Where is the effort force?
Where is the resistance force? C B A

6. Applying force and doing work
W = Fd (Work = Force ٠ distance)
W = F ٠ d
Measured in Joules (J)
You push a box with a force of 200N. The box moves 1m. How much work did you do?
W = 200N x 1m
W = 200J
Joule = 1 N/m

7. Applying force and doing work
A girl lifts a 12N (a) weight 1.5m (b) How much work does she do on the weight?
F =
d =
W = Fd
Joule = 1 N/m

8. Applying force and doing work
REMEMBER energy is always conserved so…..
You never get more work out than you put in
Win = Wout (in an ideal machine)
Why will work out always be smaller?
Wout is always smaller because some heat is given off due to friction
Why would work out be smaller?
Discussion p 181

9. The Simple Machines

11. LEVERS A bar that is free to pivot, or turn, about a fixed point
FULCRUM = the fixed point of a lever
EFFORT ARM = the part of the lever on which the effort force is applied
RESISTANCE ARM = the part of the lever that exerts the resistance force

12. LEVERS Teeter-totter, can opener, tennis racket
Helps you do more work with the strength you already have

13. 3 TYPES OF LEVERS
FIRST CLASS = fulcrum is between the effort and resistance forces (teeter-totter)
Multiplies the effort force and changes its direction
Effort moves farther than Resistance.

14. 1st Class Lever
When the fulcrum is closer to the effort than to the load:
there is a loss in force
There is a gain in speed and distance.

15. 1st Class Lever
When the fulcrum is closer to the load than to the effort:
there is a loss in speed and distance
There is a gain in force.

16. 1st Class Lever
When the fulcrum is midway between the effort and the load:
there is no change in force, speed or distance

17. 3 TYPES OF LEVERS
SECOND CLASS = resistance is located between the effort force and the fulcrum (wheelbarrow)
Always multiplies effort force
Effort moves farther than Resistance.

18. 3 TYPES OF LEVERS
THIRD CLASS = effort force is located between the resistance force and the fulcrum (fishing pole)
Increases speed (cannot multiply the force)
Resistance moves farther than Effort.
Multiplies the distance the effort force travels

19. How well do you know your levers?
Crowbar – 1st and scissors
Bottle opener – 2nd and nutcrackers
Shovel – 3rd and broom
1st class B. 2nd class C. 3rd class

20. Pulleys
A grooved wheel with a rope, chain, or belt running along the groove
Flagpole, blinds
The two sides of the pulley are the effort arm and resistance arm
WHAT DOES A PULLEY DO?
changes the  direction of the force
makes it easier to lift things to high-rise areas.
There are 3 types of pulleys

21. Fixed Pulley
A fixed pulley is attached to something that does not move
Changes the direction of the effort force.
to pull or push  the pulley up and down.
Disadvantage: have to apply more effort than the load
Acts as a first class lever with the fulcrum located at the axis – instead of a bar, the pulley uses a rope or a chain

22. Movable Pulley A movable pulley moves with the load
May be attached to a construction crane
Does multiply the effort force
Cannot change direction of the effort force.
Mechanical advantage is the effort distance divided by the resistance distance.
Disadvantage: have to pull or push the pulley up or down.
Advantage: less  effort to pull the load.
Acts as a second class lever

23. Block and Tackle Pulley
A movable pulley and a fixed pulley
the effort needed to lift the load is less than half the weight of the load.
Advantage: effort is less than half of the load.
Disadvantage: travels a very long distance.

24. Wheel and Axle a lever that rotates in a circle around an axle.
Two wheels of different sizes connected - the axle being the smaller wheel.
Larger wheel may be a crank handle or faucet handle
Door knob, water faucet

25. Wheel and Axle A GEAR is a wheel with teeth along its circumference
Effort is exerted on one gear to cause the other gear to turn

26. Inclined Plane A plane is a flat surface
Inclined plane is a plane that is slanted
Ramp
Used to move things from a lower to higher place or vice versa

27. Inclined Plane
How does the amount of work done with a ramp compare to the amount of work done lifting the object?
Will be the same
Force to lift would be greater than the force use to push
Distance pushed up the ramp would be farther than distance lifted
NOT LESS WORK, BUT LESS EFFORT, HELPS to overcome the force of gravity when lifting or lowering an object

28. Screw an inclined plane wrapped around a cylinder.
Multiplies an effort force by acting through a long effort distance.
The closer the threads on a screw, the greater the mechanical advantage
The plane actually slides through the wood

29. Wedge An inclined plane with one or two sloping sides that moves
The wedge used to increase force. 
The material remains in place while he wedge moves through it.
A wedge changes the direction of the input force.
Ax, knife, chisels
The "sharper" the wedge, the greater the mechanical advantage.
Can be used to split, cut, or fasten (nail/doorstop)

30. Compound Machines A combination of two or more simple machines
Lawn mower
Pencil sharpener Ax
Bicycle
Honda - The Cog