Ppt Levers

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