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:

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)

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

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.

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.

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?

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