Simple Machines & Mechanical AdvantageRHS Technology Education

Simple Machines are Designed to…

• Transfer kinetic energy (the energy of motion) • Reduce the effort needed to move a load• Change the direction or amount of motion• Change the type of motion (rotary to

straight line)

Mechanical Advantage

• What is Mechanical Advantage?• a measure of how much the effort is decreased by the

simple machine.

• Ideal Mechanical Advantage (IMA) ignores internal friction

• How do I calculate IMA?• IMA=Effort distance/Resistance distance

Lever

• A lever is a stiff bar which rotates around a point called the fulcrum.

• Can you list some examples of a lever?

1st Class Levers

2nd Class Lever

3rd Class Lever

Mechanical Advantage of Lever

• IMA= Effort Arm (Effort to Fulcrum)/Resistance Arm (Resistance to Fulcrum)

Wheel and Axle• A Wheel & Axle change rotary motion into linear motion• IMA= Wheel Radius/ Axle Radius

Fixed Pulley

Movable Pulley

Block & Tackle

The Three Types of Pulleys

Pulley• IMA = is determined by counting the number of supporting

ropes• Last one over top does not count!

Inclined Plane

• IMA= Length of Slope/ Height of the Slope

Wedge

• IMA= Length of Sloped Edge / Separation Surface

Effort

Inclined Plane

Effort

Wedge

Inclined Plane vs. Wedge

ScrewA screw works by using a twisting motion to create torsion

Screw• IMA= 3.14x Diameter/Distance between threads (lead)

Practice Problem• Calculate the

mechanical advantage of the screw shown

• In this example:• The diameter is (1/4)”

• The lead is 1/20

• What is the IMA of this screw?