Simple Machines Workshop - Macomb Science Olympiad · 2019-08-16 · Simple Machines Workshop - Artie & George Martin Trade offs To increase the force on the load we must increase

Macomb Elementary Science Olympiad - Feb 2014Simple Machines Workshop - Artie & George Martin

SimpleMachinesWorkshop


What is a Simple Machine?

Definition: A simple machine is a device, or tool, which

makes work easier.


IdentifyingSimple Machines


Inclined Plane


Wedge


Lever


wheeland axle


Pulley


Screw


Compound Machines


What does a Simple Machine do?

• A Simple Machine increases the usefulness of a force by changing . . .


The Strength of the force


How far the force moves


The speed

of the

force


Or,the

directionofthe

force


What is Work?Work is performed by applying

a force over a distance.

or

Work = Force X Distance


Work FormulasIf there are no friction losses (Ideal Machine),

the work effort applied is equal to the work done on the load.

Work in = Work out

or

Force in X Distance in = Force out X Distance out

NOTE: For our purposes, all simple machines will be considered to be “Ideal”.


When the force applied to the load is more than the effort, we call that

Mechanical Advantage


Mechanical AdvantageCan be expressed as a ratio:

MA = Force out Force in

This ratio can also be expressed as:

MA = Distance in Distance out


Trade offsTo increase the force on the load we must increase the distance traveled by the effort.

If the effort must move farther, it must also move faster.

Sometimes we give up force (MA < 1) to get more distance or speed

Sometimes there is no change in the force (MA = 1) we only want to change the direction of the force.


How does an inclined plane work?

The only Simple Machine that does not move

To determine the MA of an inclined plane, compare the length of the ramp to the height.

MA = Length Height


How does a wedge work?

Effort is applied to the wedge

Direction is changed by ~90o

Estimate the mechanical advantage by comparing the length of the wedge by its width

MA = Length Width


Levers

“Give me where to stand, and I will move the earth.” - Archimedes (287-211B.C.)


Parts of a lever

EffortFulcrum

Load


1st class leverAlways changes the direction of the force

May change the strength of the force

May change how far, and how fast, the forces move


2nd class lever

Does not change the direction of the force

Increases the force on the load

Effort always moves farther, and faster, than the load


3rd class lever


Requires MORE effort to move the load (MA < 1)

Purpose is to gain distance and speed


Definitions:

Fulcrum - The support about which a lever pivots.

Effort Arm - The distance from the applied force or effort to the fulcrum

Load Arm - the distance from the load to the fulcrum


Estimate the mechanical advantage by comparing the length of the Effort

Arm to the length of the Load Arm

For Example: MA = Effort Arm Load Arm


Wheel and AxleChanges the strength of the force

Changes how far, and how fast, the load moves



Wheel and AxleEstimate the mechanical advantage by comparing the diameter of the wheel to the diameter of the axle

MA = Wheel diameter Axle diameter


Pulleys

May increase force on the load

May change distance or speed

May change direction of the force


Calculating Mechanical advantage of a pulley

Count the number of parts of the rope

supporting the load

MA = 2


MA = 3

MA = 4


Screw

Changes the direction of the force (rotating effort changes to linear motion - approx. 90o)

May change strength of the force

May change the distance and speed


d

To estimate the mechanical advantage of a screw:

Determine the pitch ( p) of the screw. This tells you how far the screw moves with one complete rotation.

Find the circumference of the screw. Measure the diameter (d) and multiply by pi (π)

MA = π d p


Practice























The Competition

10 Stations

2 Minutes per station


Station #1


BA

C


Station #2



Times Up


Station #1

Identify the simple machine(s) found in the object displayed

1) Lever A. Yes B. No2) Pulley A. Yes B. No3) Inclined Plane A. Yes B. No4) Screw A. Yes B. No5) Wedge A. Yes B. No6) Wheel and Axle A. Yes B. No

A B

C


Station #17) Which labeled point is the Fulcrum?

A. AB. BC. C D. Not labeled

8) At which labeled point is force applied to the Load?

A. AB. BC. CD. Not labeled

9) At which labeled point is the Effort applied?

A. AB. BC. C D. Not Labeled

10) Does any part of this machine change the direction of the force?

A. YesB. No

AB

C


Station #2

Identify the simple machine(s) found in the object displayed

1) Lever A. Yes B. No2) Pulley A. Yes B. No3) Inclined Plane A. Yes B. No4) Screw A. Yes B. No5) Wedge A. Yes B. No6) Wheel and Axle A. Yes B. No


Station #217) Does any part of this machine change the direction of force?

A. YesB. No

18) Is the force on the load less than or greater than the effort applied?

A. Less ThanB. Greater Than

19) Which moves faster?

A. EffortB. Load

20) Which moves farther?

A. EffortB. Load

Documents

Simple Machines Workshop - Macomb Science Olympiad · 2019-08-16 · Simple Machines Workshop - Artie & George Martin Trade offs To increase the force on the load we must increase