Simple Machines and Work An interactive unit designed to guide the understanding of 7 th grade students Simple Machines are those machines that are made.

Simple Machines Simple Machines and Workand Work

An interactive unit designed to guide the understanding of 7th grade students

Simple Machines are those machines that are made up of only 1 machine !!!

Are these devices simple machines????

By Lucas Kraschnewski

DirectionsDirectionsThis unit Simple Machines and Work is

divided into 9 chapters:

Each chapter will have a variety of learning opportunities for you to investigate each topic

including:

(These 5 links are not active, 9 links above are active)

ProcessProcess1. Starting with Ch. 1, proceed through each

unit in order until reaching the end of Ch. 9

2. Complete each chapter in the following order:

A. Read and examine the notes page

B. Watch a video on the topic (if available)

C. Apply your understanding by watching / completing the animations and/or simulations

D. Go to the provided links to gain a deeper understanding

E. Complete the short quiz on each topic to assess your knowledge and e-mail results to teacher

F. Print Lab worksheets provided : complete / turn in

3. After finishing Ch. 9, complete the Unit Exam4. Complete the Rube Goldberg project as your

“Final”

Chapter 1 -Mechanical Chapter 1 -Mechanical Advantage (MA)Advantage (MA)

Definition: The number of times a machine multiplies your input force (effort)

or

How many times easier a job becomes because of using the machine

Before beginning complete the pre-quiz to the right. Check your answers and then e-mail your results to your

teacher. Your score will not be a factor at this point.

If a machine has a MA of 4, that means the machine being used makes your job 4 times easier to do than if you did

that same job without the machine!

Index

Mechanical Advantage Mechanical Advantage (MA)(MA)

Question #1: If a box weighs 50 Newtons, how much force do you have to apply to the box to lift it or slide it?

Answer: 50 Newtons (That’s how heavy the box is!!)

Now, let’s say you use a pulley machine to lift the box. The box still weighs 50 Newtons, but you notice you don’t have to lift as hard? You only lift with 25 Newtons of force and the box still can be picked up off the floor.

Has the machine made your job easier? Yes

How much easier? 2 times easier or you only work ½ as hard!!

The MA of the Pulley is 2

Mechanical Advantage Mechanical Advantage (MA)(MA)

Can you calculate how much a machine will help you (determine the MA) before you actually use it??

YES !

Procedures to Calculate MA for the simple machines:

Inclined Planes: Length of Ramp

Ramp Height

Pulleys: Count the number of ropes that are supporting (attached) to the object being liftedWheel and Axle: Wheel Radius

Axle Radius

Output Force Input ForceOr

You can use this formula for any of the simple machines

Ch.2-What is Work???Definition: When a force is exerted on an object and that

object moves in the direction the force is being applied

Work = Force X Distance

How hard you push or pull on

the object

How far you move the

object

Machines never reduce the amount of work you do! They make the work easier by requiring you to apply less force,

but over a longer distance!

Index

Work Question: Who is working?

A. Person #1

B. Person #2

C. Both#1.

#2.

Person #2 is not working because he is lifting up on the weights, but they are not moving up!!

Person #1 is working because he is lifting up on the bar and the bar is moving up!!

Ch. 3 - Power!!!Why is this considered a power tool?

Because ….. This electric jackhammer will break apart the concrete faster than he could break the concrete apart by hand!

Definition: The rate (how fast or slow) at which work is done

If Josh and Bill both lift 150N of weight over their heads, to a height of 3 m while exercising, but Josh lifts that weight in 2 seconds and it take Bill 4 seconds, who does more work?

Question-Question-

Neither!! They do the same work (F X D or 150 X 3 = 450J) But….

Josh has more power because he does the same work in less time!!

Index

Chapter 4 – Inclined Planes

Definition: Sloping surface that connects 2 points

T / F If you want to slide the box up onto the table and not just lift it straight up onto it, using these inclined planes will reduce the amount of work you have to do?Will these ramps make your job easier? YES!

How can this machine make your job easier, but not reduce the amount of work you do????

10 meters

5 meters

Which one will make your job the easiest?

Index

Inclined Planes

Check It Out!!!* The longer the ramp, which is actually the distance from point A to point B in the diagram, the easier the work becomes (less

force).* You can apply less force to move the car up the ramp, but

you move the car a longer distance. The amount of work you do is the same with all 3 ramps. Remember: Work = Force X

Distance

A

B

Chapter 5 -ScrewsDefinition: An inclined plane wrapped in a spiral

Try this before moving on!!1. Make 2 right triangles of different lengths, but with the same height.

For example-

2. Bold the long edge of each inclined plane.

3. Wrap one of the triangles around the pencil.

4. Repeat step #3 with the second triangle on a second pencil.

Index

ScrewsLook at those 2 “screws” you just created. What do you notice?*You should see that the purple screw has tighter threads!!

Which screw would be easier to turn into a block of wood? Why?The purple screw, because it started as an inclined plane with a longer ramp, and you should have learned that the longer the ramp the easier your job becomes.

Question:

Why do mountain roads wrap around the mountain and not just go straight up and over the mountain?

Why do we have spiral staircases?

Think About It!!

Chapter 6 –What do doorstops, shovels, and axes all have in common??

Wedges

Definition: a double inclined plane placed back to back

Index

WedgesThink about the difference between trying to dig up solid ground with a square shovel vs. a spade shovel.

Which is easier to use? Why?

The longer the ramp length, the easier the

work becomes!!

Where are wedges used?

-Knives

-Arrows

-Screwdrivers

Definition: Bar that pivots on a fixed point called the Fulcrum

Fulcrum (Pivot Point)

1st Class

2nd Class

3rd Class

3 Types3 Types

Effort ArmResistance

Arm

Chapter 7 - LeversThe end you

push down on

The end the object being

moved sits on

Index

1st Class Levers

* Fulcrum is between the load and the Input Force*

Load = Box (what is being moved)

Input Force = Where you push on the bar (far right in this case)

The longer the Effort Arm is compared to the Resistance Arm, the easier the work becomes!!

Generally speaking: Longer bar = Easier work

The Load and Input Forces move in

opposite directions

2nd Class Levers

*Load is between the fulcrum and input force*

Load and Input Force both move in the same direction!!

Fulcrum

Load

Input Force

Fulcrum

Load

Input Force

Again, a longer bar will make work easier, but

the longer the bar is, the farther you must lift that

bar

Work amount isn’t reduced!!

3rd Class Levers

* Input Force is between the Load and Fulcrum*

Fulcrum

Input Force

Load

WARNING: Your effort is actually going to be more than the load you are moving!!

Chapter 8 - PulleysDefinition: A machine made with a rope or cable wrapped around a grooved wheel

Pulleys can make work easier by:

A. Reducing the amount of required effort force

B. Changing the direction of the load

1. Fixed2. Movable

3. Block & Tackle

Index

Fixed PulleysAdvantageAdvantage

Changes direction of load for you

For Example:

In a hayloft, you can lift bails up by pulling down on the rope, so you don’t need to climb a ladder each time!

DisadvantageDisadvantage

You apply more force than the load weighs due to friction

Flag

Pol

e Curtain

- Wheel does not move!!

Moveable Pulleys- Wheel moves in same direction you lift on

rope!!

Advantage

Less force (effort) is

required to lift object

Disadvantage

You must lift up on rope a long distance to move the object a very short distance

Block and Tackle Pulleys

- Combination of a fixed and movable pulley

-Very little effort is needed to lift objects

- Must pull rope very long distance to move object short distance

Chapter 9 – Wheel and Axle

DefinitionDefinition: Machine made of 2 attached circles, one being small and one being large in size

By turning the small circle (axle) a short distance, the larger circle (wheel) travels a long distance!!

Index

Wheel and AxleGears = wheel and axle with teeth!

* Great examples of how the small wheel (axle) turns many times compared to the larger wheel

Unit Review1. Check out the following websites and video as a review first.

2. Then complete the 2 quizzes on the right and print/email your results

-Remember –

No machine reduces the amount of work….they make the work easier!!

Final Project – Rube Goldberg Machines

1. What is a Rube Goldberg Machine?

3. What are my final project requirements?

2. Background info. on Rube Goldberg

Would you want to try to enter the National Rube Goldberg Machine Contest???

Rube Goldberg Machines Rubrics

Click Image to View Project #1 Rubric

Click Here for Project #2 RubricPrint Y

our

Rubric!!

ReferencesReferences

Click to see complete website reference list

Print : Student Activity Check List

Make sure you have e-mailed or printed evidence of completion of all 8 daily quizzes and the 2 Unit

Review Quizzes

Print o

ff ALL Rube

Goldberg Project WS

Begin working on

Rube Goldberg

Machines!!

Producer: Mr. Kraschnewski

[email protected]