1. Gr. 8 Science: Mechanical Efficiency
Work & Simple Machines
Work is when a force is applied on an object and the object moves a distance in the direction of the force
Work is measured in Joules (N.m) named after the scientist James Prescott Joule
Work is calculated using the formula triangle below:

2. Gr. 8 Science: Mechanical Efficiency
Work & Simple Machines: Mechanical Advantage
We use simple machines to make work easier
Mechanical Advantage (M.A.) is a ratio that indicates how well a machine is increasing our human effort
It is calculated using this formula:
M.A. = Load force ÷ Effort Force (no units)

3. Gr. 8 Science: Mechanical Efficiency
Work & Simple Machines: Mechanical Advantage
Load force is the force of gravity acting on the object you are trying to move
Effort force is the force a human exerts while using a simple machine
The higher the mechanical advantage of the simple machine the easier (less force) it is to use

4. Gr. 8 Science: Mechanical Efficiency
Work & Simple Machines: Levers
There are three classes of levers that are used in the work world
These are Class 1, Class 2, and Class 3 levers
Some key parts of the lever are the fulcrum, pivot point, load arm, and effort arm
We will discover which class of lever has the highest M.A and know why.

5. Gr. 8 Science: Mechanical Efficiency
Work & Simple Machines: Pulleys
There are three types of pulley set-ups that are used in the work world
These are the single fixed pulley, single movable pulley, and the combination pulley
Some key parts of a pulley system are the wheel , rope or chain, and axel
We will discover which pulley set-up has the highest M.A. and know why.

6. Gr. 8 Science: Mechanical Efficiency
Work & Simple Machines: Gears
Gears are wheels made from metal that have teeth
A gear train consists of two or more wheels working together
Gear ratio is the ratio of the two circumferences of the gears in a gear train
Think about what bike gear is ideal for climbing hills and why?

7. Gr. 8 Science: Mechanical Efficiency
Work & Simple Machines: Ramps
Ramps are commonly found in most buildings to allow access for people in wheelchairs
Where else can you find ramps in our society?
Think about how ramps make our life easier…
We are going design our own ramp and experiment with some friction variables