1. Unit 4: (2) Simple Machines

2. MACHINES
A machine is a device that makes work easier by changing the size or direction of a force.
Machines apply force over bigger distances, meaning less force will be needed (than doing it the hard way).

3. What is a Simple Machine?
A machine that does work with one movement is a simple machine.
A simple machine has few or no moving parts.

4. Simple Machines
All other machines are a combination of the 6 simple machines.

5. Wheels and Axles The wheel and axle are a simple machine
The axle is a rod that goes through the wheel which allows the wheel to turn
Gears are a form of wheels and axles
Steering wheel, screwdriver, doorknob are all examples

6. 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

7. Inclined Planes
Inclined Plane is a slanted surface along which a force moves an object to a different elevation
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. 

8. Wedges
A wedge is a V-shaped object whose sides are two inclined planes sloped toward each other
Wedges are used to split things.
Examples:
knife, axe, needles, nails, bullets

9. Screws
A screw is an inclined plane wrapped around a shaft or cylinder.
The inclined plane allows the screw to move itself when rotated.
Nuts and Bolts

10. Levers-First Class
In a first class lever the fulcrum is in the middle and the load and effort is on either side
Think of a see-saw

11. Levers-Second Class
In a second class lever the fulcrum is at the end, with the load in the middle
Think of a wheelbarrow

12. Levers-Third Class
In a third class lever the fulcrum is again at the end, but the effort is in the middle
Think of a pair of tweezers

13. Machines 1. Lever 2. Wheel & Axle 3. Inclined Plane 4. Lever 5. Wedge

14. Simple Machines
Simple Machines can be put together in different ways to make complex machinery

15. Compound Machines
Combination of two or more simple machines that operate together
Watch- complex series of gears, so that one gear drives the next
Gears-special type of wheel and axle
bikes

16. MACHINES The work/energy you do on a machine is called work input.
The work being done by the machine on the object is called work output.

17. MACHINES Work output can never be greater than work input.
You can’t get more than you give.

19. WORK and MACHINES
According to the Law of Conservation, work output should equal input,
but it doesn’t because of friction.
Part of the work input must be used to overcome the friction created by the use of the machine.

20. WORK and MACHINES
The less friction it has to overcome, the more efficient the machine is.
Efficient means there is no waste.
What are some things we do to reduce friction in machines?
oils, greases, aerodynamics

21. WORK and MACHINES
The mechanical efficiency of a machine is a percentage that compares work input to work output.
Mechanical Efficiency = output work x 100%
input work

22. Machines and Mechanical Advantage
Mechanical Advantage measures how much a machine multiplies force or distance.
A machine can
Make work easier
Redistribute work
Change size or direction of input force
Increase output force by changing distance over which force is applied

23. This brings us to MECHANICAL ADVANTAGE!!!
A.M. A. = output force I.M.A = input distance
input force output distance
(Actual) (Ideal)
AMA compares forces
IMA compares distances
AMA is less than IMA.
Mechanical advantage is a ratio so it does not have units!
For a machine to be helpful, its mechanical advantage must be greater than MA>1

24. Actual Mechanical Advantage
A.M.A compares forces.
Actual Machines:
take into account energy loss due to deflection, friction, and wear
AMA is always less than IMA
Because some energy is always lost in overcoming friction.

25. Actual Mechanical Advantage

26. Mechanical Advantage Fin Fout Fin = 20 N AMA = Fout ÷ Fin Fout = 500 N
A worker applies an effort force of 20 N to open a window with a resistance force of 500 N. What is the crowbar’s AMA?
GIVEN:
Fin = 20 N
Fout = 500 N
AMA = ?
WORK:
AMA = Fout ÷ Fin
AMA = (500 N) ÷ (20 N)
AMA = 25
AMA
Fout
Fin

27. Mechanical Advantage Fin Fout Fin = ? Fin = Fout ÷ AMA Fout = 2000 N
Find the effort force needed to lift a N rock using a jack with a mechanical advantage of 10.
GIVEN:
Fin = ?
Fout = 2000 N
AMA = 10
WORK:
Fin = Fout ÷ AMA
Fin = (2000 N) ÷ (10)
Fin = 200 N
AMA
Fout
Fin

28. Ideal Mechanical Advantage
I.M.A compares distances.
Ideal machines:
Assumes there is NO energy loss due to deflection, friction, and wear
Power into the machine = Power out of the machine

29. Mechanical Advantage Dout Din IMA Din = 1.8m Din ÷ Dout Dout = 0.3m
If a mechanic drives a car 1.8 m along a ramp to raise a car 0.3 m, what is the ideal mechanical advantage (IMA) of the ramp?
GIVEN:
Din = 1.8m
Dout = 0.3m
IMA = ?
WORK:
Din ÷ Dout
IMA = (1.8m) ÷ (0.3m)
IMA = 6
IMA
Din
Dout