Levers and Mechanical Advantage

1
Levers and Mechanical Advantage
2
New Vocabulary

• Effort force the force YOU put in
• Resistance force the force of the machine

resistance force
3
Mechanical Advantage

• Compares your force with the force of the machine
• Which one should be bigger?
• The force of the machine!
• Sothe MA measures how many times the force of
  the machine (resistance force) is greater than
  your force (effort force)

4
How do we measure MA?

• Compare the resistance force to the effort force
• Fr / Fe

5
Ideal vs Actual MA

• What is your ideal class like?
• No work, sleeping, etc
• Ideal means perfect!
• In a perfect world, the machines would not have
  to fight against air resistance or friction-they
  have the ideal MA.
• But we know that we live in the actual or real
  world where we have to do work in class!
• In the real world, the machines have to account
  for air resistance and friction-they have Actual
  Mechanical Advantage (AMA).

6
What does this have to do with work?

• Remember that Work Force x Distance
• So this same equation applies to the work done
  by machines.
• Work done by you should be equal to the work done
  by the machine!
• The machine does the same amount of work, it just
  makes it easier for you!

7
Connections to Work

• W (by you) W (by machine)
• Fe x de Fr x dr

8
Levers

• Definition a lever is a bar that is free to turn
  around a fixed point (called a fulcrum)

9
Types of Levers

• 1st Class
• Fulcrum is in the middle of bar

10
Types of Levers

• Examples of 1st class levers
• Seesaw, crowbar,
  scissors

11
Types of Levers

• 2nd Class
• Fulcrum is on one end

12
Types of Levers

• Examples of 2nd class levers
• -boat oars, bottle opener, wheel barrow

13
Types of Levers

• 3rd class
• Fulcrum on one end

14
Types of Levers

• Examples of 3rd class levers
• Baseball bat, shovel, golf club, broom

15
Review Levers
16
Review Levers
17
Review Levers
18
Review Levers
19
LEVER MOVIE