1. What do simple machines do for us anyway?
Mechanical Advantage
What do simple machines do for us anyway?

2. There are four ways that a machine helps us to do work.
Transfers our effort force from one place to another. Ex: seesaw
Multiply your effort force Ex: crowbar
Magnify speed and distance Ex: baseball bat
Changing the direction of the force. Ex: pulley on the flagpole

3. There are 2 types of mechanical advantage.
IMA – Ideal mechanical advantage.
This is the number of times a machine is designed to multiply your effort force.
It is based on measurements of the machine.
Ignores friction
AMA – Actual mechanical advantage
This is the number of times the machine actually multiplies your effort force.
AMA = resistance force/effort force.
Includes the effects of friction
IMA is always larger than AMA.

4. Mechanical Advantage Definition
- a quantity that measures how much a machine multiplies force or distance
Two types
Actual: measures the actual forces action on a machine
- AMA = output force
input force
Ideal: measures the mechanical advantage in the absence of friction
- IMA = input distance
output distance

5. Mechanical Advantage Problems
Q: Alex pulls on the handle of a claw hammer with a force of 15 N. If the hammer has a actual mechanical advantage of 5.2, how much force is exerted on a nail in the claw?
A: output force = (5.2)(15N) = 78 N
Q: If you exert 100 N on a jack to lift a 10,000 N car, what would be the jack’s actual mechanical advantage (AMA)
A: AMA= 10,000 N / 100 N = 100

6. Mechanical Advantage Problems
Q: Calculate the ideal mechanical advantage (IMA) of a ramp that is 6.0 m long and 1.5 m high? A: IMA = 6.0m / 1.5m = 4.0 Q: The IMA of a simple machine is 2.5. If the output distance of the machine is 1.0 m, what is the input distance? A: Input distance = (2.5)(1.0m) = 2.5 m

7. Efficiency of Machines
Definition
- a quantity, usually expressed as a percentage, that measures the ratio of useful work input
Formula
- Efficiency = useful work output
work input
- % of work input that becomes work output
- due to friction, efficiency of any machine is always less than 100%

8. Efficiency Problems
Q: Alice and Jim calculate that they must do 1800 J of work to push a piano up a ramp. However, because they must also overcome friction, they must actually do 2400 J of work. What is the efficiency of the ramp? A: 1800 J/ 2400 J x 100 = 75% Q: If the machine has an efficiency of 40%, and you do 1000 J of work on the machine, what will be the work output of the machine? A: Work Output = (Efficiency x work input) / 100% Work Output = (40% x 1000 J) / 100% = 4.0 x 102 J

9. Simple Machines Definition - one of the six basic types of machines
2 types or families
1. lever
2. inclined planes

10. Levers
Definition
- a rigid bar that is free to move around a fixed point
ex. screwdriver
all levers have a rigid arm that turns around a point called the fulcrum
force is transferred from one part of the arm to another
original input force can be multiplied or redirected into output force
levers are divided into 3 classes, based on the locations of the input force, output force, and the fulcrum

11. 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

12. 1st Class Lever Changes the direction of the force
Multiplies effort force
Magnifies speed and distance
Ex: seesaw, crowbar, scissors

13. 2nd Class Lever Multiply effort force
Mechanical advantage is always greater than 1.
Ex: bottle opener, boat oars, wheel barrow

14. 3rd Class Lever Magnifies speed and distance
Mechanical Advantage always less than 1
Ex: baseball bat, golf club, broom, shovel

15. Wheel and Axis Definition
- simple machine that consists of two disks or cylinders, each one with a different radius
ex. steering wheel, screwdriver
made of a level or a pulley (wheel) connected to a shaft (axle)
small input force, multiplied to become a large output force

16. Inclined Planes Definition
- slanted surface along which a force moves an object to a different elevation
ex. knife, ax, zipper, wedge, screw
ramp redirects the force applied to lift object upward
turns a small input force into a large output force by spreading the work out over a large distance
- wedge: functions as two inclined planes back to back, turning a downward force into two forces directed out to the sides
-screw: an inclined plane wrapped around a cylinder

17. Pulleys
Definition
- a simple machine that consists of a rope that fits into a groove in a wheel.
- very similar to a lever
point in the middle of the pulley is like a fulcrum
rest of the pulley acts like the rigid arm
3 Types of Pulleys
- fixed pulleys
- moveable pulleys
- pulley system

18. Fixed And Movable

19. Pulley System

20. 1. What is the IMA of this pulley system. 2
1. What is the IMA of this pulley system? Ignoring friction, if you want to lift the resistance 3 meters what will the effort distance be? Ignoring friction how much effort force will be necessary to lift a load of 15 newtons? 4. How much work is done?

21. Compound Machines Definition
- a machine that is made of more than one simple machine
ex. scissors, jacks, bicycle, washing machine, car, clock