Levers and
Mechanical Advantage
New Vocabulary…
Effort force = the force YOU put in
Resistance force = the force of the machine
resistance force
Mechanical Advantage
Compares your force with the force of the machine
Which one should be bigger?The force of the machine!So…the MA measures how many times
the force of the machine (resistance force) is greater than your force (effort force)
How do we measure MA?
Compare the resistance
force to the effort force…
Fr / Fe
Ideal vs Actual MAWhat is your ideal class like?No work, sleeping, etcIdeal 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 MA.
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!
Connections to Work…
W (by you) = W (by machine) Fe x de = Fr x dr
resistance force
effort distance
resistance distance
THIS IS A TYPE OF LEVER!!!
Levers
Definition: a lever is a bar that is free to turn around a fixed point (called a fulcrum)
Types of Levers
1st Class–Fulcrum is in the middle of bar
Types of Levers
Examples of 1st class levers:Seesaw crowbar
scissors
Types of Levers
2nd ClassFulcrum is on one end
Types of Levers
Examples of 2nd class levers: boat oars bottle opener wheel
barrow
Types of Levers
3rd class
Fulcrum on one end
Types of Levers
Examples of 3rd class levers:Baseball bat, shovel, golf club, broom
Review Levers
Review Levers
Review Levers
Review Levers