Simple Machines

PhysicsMrs. Coyle

What are some simple machines?

• Lever

• Incline Plane

• Pulley

Simple Machines

• Multiply the effort force (allows you to use a smaller effort force to raise a heavier object).

• Change the direction of the force.

• Do not reduce the work input.

Archimedes: ”GIVE ME A PLACE TO STAND AND I WILL MOVE THE EARTH”

http://www.math.nyu.edu/~crorres/Archimedes/Lever/leverBigCorners.gif

Lever

Mechanical Advantage

MA= Output Force(Weight of Object)

Input Force (Effort)

• MA shows how much you are multiplying your effort force.

What is the trade off?

• What happens to the effort distance, when a machine multiplies the effort force?

• Answer: Effort distance increases

Ideal Mechanical Advantage

• IMA= Effort Distance (din )

Output Distance (dout )

• IMA is equal to MA in the absence of friction (ideal case).

IMA for a Lever

• IMA= Effort Distance = Effort Arm

Output Distance Load Arm

Problem

What is the ideal mechanical advantage

of the lever shown?

IMA=3

FulcrumLoadEffort

Lever

• http://www.walter-fendt.de/ph11e/lever.htm

Types of Levers

• Type1

• Type 2

• Type 3

Incline Plane

http://www.edinformatics.com/math_science/simple_machines/Inclined_plane.gif

dIN

dOUT

Problem: Which has a greater IMA?

A B

Problem: Find the IMA.

10m5m

Pulleys

Pulleys

Single Fixed Pulley

Ideally:

Win=Wout

Findin= Foutdout

IMA= din /dout =1

Single Moveable Pulley

IMA= 2

Combination of Fixed and Moveable Pulleys

IMA= 2

IMA for Pulleys

• The IMA of pulleys can quickly be found by counting the number of lifting strands.

Question

What is the IMA of the following pulleys?

Efficiency• Efficiency indicates the percentage of the

input work that was converted to useful work and not lost to friction.

• % eff = (Wout / Win) x 100 %

• % eff = (MA / IMA) x 100 %