14 4 Simple Machines (A)

14.4 Simple Machines What are the Six types of simple

Machines?

What determines the mechanical advantage of the six types of simple machines?

http://www.nvsd44.bc.ca/sites/ReportsViewOnePopM.asp?RID=3812 http://www.uark.edu/depts/aeedhp/agscience/simpmach.htm

Compound Machine Simple Machines

The Six Simple Machines

• Lever

• Wheel and Axle

• Inclined Plane

• Wedge

• Screw

• Pulley

3 Classes of Lever

• Lever = a rigid bar that is free to move around a fixed point (Fulcrum).

3 Classes of Lever

• First class Lever = The fulcrum is between the load force (FL) and the effort force (FE).

• Ex: a teeter totter, • MA = Can be 1 , Greater Than 1, or

Less Than 1.

Fulcrum is between EF (effort) and RF (load)Effort moves farther than Resistance. Multiplies EF and changes its direction

3 Classes of Lever

• Second class Lever =The load force (FL) is between the effort force (FE) and the fulcrum.

• MA = Always Greater Than 1• Ex. Wheelbarrow

RF (load) is between fulcrum and EF Effort moves farther than Resistance.

Multiplies EF, but does not change its direction

3 Classes of Lever

• Third class Lever = The effort force (FE) is between the fulcrum and the load force (FL).

• MA = Always Less Than 1

• Ex. Rake or Broom

EF is between fulcrum and RF (load) Does not multiply force

Resistance moves farther than Effort.

Multiplies the distance the effort force travels

3 Classes of Lever

• The mechanical advantage of a lever is the ratio of the length of the lever on the effort force side of the fulcrum to the length of the lever on the resistance force side of the fulcrum.

*Wheel & Axle

• The wheel and axle consists of a large wheel rigidly secured to a smaller wheel or shaft, called an axle

• The mechanical advantage is the ratio of the radius of the wheel to the radius of the axle {radius of Wheel / radius of axel}

Mechanical advantage is 5:1 or 5

Inclined Plane

• Is an even sloping surface• The mechanical advantage is

equal to the length of the slope divided by the height of the inclined plane

•EX. Ramp

Wedges & Screws

• The Wedge and Screw are a modification of the inclined plane.

• Wedges are used as either separating or holding devices.

• Thin wedge has greater IMA than thick of the same length.

• Screw with close threads have greater IMA.

MA of an screw can be calculated by dividing the number of turns per inch.

Pulleys• A pulley consists of a rope that

fits into grooved wheel that turns freely in a frame called a block.

• Pulley System = Block and Tackle.

• Both fixed and moveable pulleys are used in combination

• Capable of both changing the direction of a force and creating a mechanical advantage

Two Types of Pulleys

• Movable Pulley

• IMA = is equal to the number of ropes that support the moveable pulley

•Fixed Pulley

•A fixed pulley changes the direction of a force; • it does not create a mechanical advantage

Compound Machines

• A machine made up of two or more simple machines that operate together

• Ex. Bicycle, Clock, Washing Machine, Car

• Inside a Clock a complex series of Gears act as a continuous Lever.