1. Mechanical Advantage vs. Mechanical Efficiency
Simple Machines

2. Machines and Work
We said that machines make work easier b/c they change the size or the direction of the force (input).
Force is measured in Newtons (N)

3. Mechanical advantage vs Mechanical Efficiency
Mechanical Advantage (MA) - tells how many times a machine multiplies force
Formula
Mechanical Advantage = output force
Input force

4. Mechanical Advantage (continued)
If your result is :
greater than 1 = the output force is greater than the input force
(this is what you want b/c you don’t want to put in more force than you get out)
less than one = it requires more input force from you and does not have a mechanical advantage

5. Practice Problems for Mechanical Advantage (MA)
You have to push a 500N weight up a ramp and have to push with a force of 50N. What is the Mechanical Advantage?
MA = output force so =
Input force
The output force is ________ times greater than the input force

6. Practice Problems for Mechanical Advantage (MA)
Grace uses a cart to lift canned foods. She uses an input force of 40 N to the cart and the cart applies an output force of 320 N . What is the Mechanical Advantage of the cart?
MA = output force so ____________ =
Input force
The output force is ________ times greater than the input force

7. Practice Problems for Mechanical Advantage (MA)
If the Mechanical Advantage a Machine is 5, what does this mean?
This means that the output force of the machine is 5 times greater than the input force

8. Mechanical Efficiency
is shown as a percent (%) that compares work output to work input.
Work is measured in Joules
Mechanical Efficiency
= work output X 100
Work input
This will give you a percentage

9. Mechanical Efficiency (continued)
**A machine cannot be 100% efficient b/c Machines have moving parts which create FRICTION which causes energy input to be lost as heat..

10. Mechanical Efficiency (continued)
QUESTION:
What is the mechanical efficiency of a machine whose work input is 100J and work output is 30 Joules ???
ME = work ouput X 100
Work input
X 100 = 30 percent
100

11. How do I remember MA and ME
** A WAY TO REMEMBER THE DIFFERENCE BETWEEN MECHANICAL ADVANTAGE AND MECHANICAL EFFICIENCY IS
MA FORCES ME TO DO WORK
(MA INVOLVES FORCE, ME INVOLES WORK)