1. Machines and Mechanical Advantage

2. What is a machine? What can it do?
Transform type of energy
Deliver energy
Increase force
Increase speed
Change direction of force
Reduce friction
In general: they help

3. Benefits of machines: mechanical advantage
Think of something very basic: a bottle opener. If you want to open a bottle, you could try to lift the cap with the force from your fingers.
or you could apply that force to a bottle opener which then transfers the force to the cap
Much easier…but why?

4. Mechanical advantage
The force you exert on the machine (the bottle opener) is called the effort force
The force exerted by the machine is called the resistance force
They are not necessarily the same
The resistance force could be greater but machine can’t do more work than you put in
So if the work can’t grow but the force can, what must change?

5. If work is the same, decreased force means increased distance.
In other words, we put in less force but over a greater distance

6. Calculating Mechanical Advantage
Mechanical advantage is the resistance force divided by the effort force.
In other words, the force you get out over the force you put in
If you put in a little force and get out a larger force, you will have a >1 MA
MA=Fr/Fe

7. Calculating MA Back to the opener:
If you exert a force of 2N on the bottle opener and it exerts a force of 4N on the cap:
MA=Fr/Fe=4/2=2
This is good- MA of >1 means it is decreasing the force you have to put in- you are gaining mechanical advantage

8. Not all machines increase the force
Can you think of an example where you put in more force and get out less? In this case you probably don’t need much force but you could get that force over a greater distance
This can also be used to increase speed- now can you think of other examples like this?

9. We use these machines to increase speed (move it through more distance)

10. As we just saw, sometimes we are not after a mechanical advantage
In fact, some machines keep the force the same but change the direction of force to make life easier on us
This pulley lets him pull down instead of lifting up- the change in direction helps him even without any MA
Changing direction