►This site was originally created for my kids and their cousins, because we did science together. We eventually added more friends and I ended up having science classes for five years. I am no longer adding to the site (since 2014), but will leave it up for others' use. I do post to facebook occasionally if I come across something to share. =)

►Please accept my apology for any broken links or videos that do not work. I am always disappointed when people take down their videos from YouTube. It makes it hard to find just the right replacement. And because the videos were posted years ago, I usually have no recollection of what the video was about.
I kept thinking I would have time after my kids graduated, but life has filled up my free time with new responsibilities. =)

►Please do not email, asking me to post your website link, or to review something to put on my site. Any resources posted on this site are things I had found on my own during my regular searching for material I needed at the time, and liked it well enough to post here. There have never been any affiliates on my site, and as it is no longer active, would not be worthwhile at this point. ;)
Thank you!

Apologia General Science, Module 4, Science, Applied Science, and Technology

What we did at Sahm-I-Am

Interactive Study Links:
• Quizlet
• Simple and Complex Machines - interactive, just for fun.  =)
• Edheads: Simple Machines - interactive, just for fun.  For simple machines, hover over the house.
• See the Inventor's Toolbox for examples of Simple Machines, then go to Gadget Anatomy to test what you learned.

• Edheads: Simple Machines
• Penny Lever lab, etc.
• Wheel and Axle
• A Screw is a kind of Inclined Plane (worksheet)
• Lever, Wheel and Axle, Pulley
• Six Simple Machines (I like the popcorn one on p. 5!)
• See these and more at Debbie's Educator's Resources  (Thanks, Debbie!)


(1)  p. 83-86a, The Distinction Between Science, Applied Science, and Technology

►Science attempts to understand how the universe and everything in it works, and how it is all interconnected.
Science is motivated by curiosity.  The goal of science is knowledge.

►Applied science takes that knowledge and applies it to improve or simplify our lives.  In other words, take the knowledge and do something useful with it.
The goal of applied science is to find a way to make something easier.

►Technology is the invention that makes things more simple or easier.
The goal of technology is to use the applied science to actually make a product that will make something more simple or easier.
Technology is not always a machine.  Technology is "any invention or process that makes life better or a job easier." -Apologia General Science, p. 84

If you do an experiment and learn something from it, that is science.
If you find a way to make something better or easier, you have applied that science.
If you actually invent something to make life better or a job easier, that is technology.


(2)  p. 86-92, Simple MachinesThe Lever

Effort is the force used to push or pull.
Load or resistance is what is being lifted or pulled.
Fulcrum is the point at where there is a hinge-like motion.
►See this picture

Read More about Simple Machines
Understanding Simple Machines

By using any simple machine to increase force or motion, you have an advantage called a mechanical advantage (or MA).  This mechanical advantage can be measured

Formula for finding the Mechanical Advantage of a Lever:
MA = (distance from fulcrum to effort) ÷ (distance from fulcrum to resistance/load)
We used the term "fe-fr" to help us remember the order.
If you look at the image of the three classes below, you will see it can take a bit of brain work to think how to apply this formula to each of these different levers.

1st class, 2nd class, and 3rd class levers
Remember FLE (or FRE):
F(orce) in the middle = 1st class
L(oad) or R(esistance) in the middle = 2nd class
E(ffort) in the middle = 3rd class

►Classes of levers animations


(3)  p. 93-95, The Wheel and Axle
Formula for finding the Mechanical Advantage of the Wheel and Axle:
MA = (diameter of the wheel) ÷ (diameter of the axle)


(4)  p. 95b-99, The Pulley
Formula for finding the Mechanical Advantage of Pulleys:
MA = count the number of pulleys!  =)
Unless there is only one pulley -- then there is NO mechanical advantage because all you did was change the direction of the pull.

And that is why, on a 20-speed bicycle for example, you have to pedal faster than on a single-speed bike (with one gear).  When the force exerted is easier, the distance will be greater.  Your pedals have to move a greater distance.  On a single-speed bicycle, you have to exert more force, but do not need to pedal as fast.


(5)  p. 99b-100, The Inclined Plane
Formula for finding the Mechanical Advantage of an Inclined Plane:
MA = (length of the slope) ÷ (height)
(This is the same as the formula for the wedge)


(6)  p. 100b-102a, The Wedge
Formula for finding the Mechanical Advantage of a Wedge:
MA = (length of the slope) ÷ (height)
(This is the same as the formula for the Inclined Plane)

I couldn't find any useful videos for the wedge.  So if you
know of any, please let me know!  =)

A wedge may look like an inclined plane, but it is used differently.
►"An inclined plane is meant to ease the force required to lift a load."
[Something moves over the surface of an inclined plane.]
►"A wedge... magnifies the force that is being applied." Apologia General Science, p. 101
[A wedge moves through something.]

Most common is the wedge used to split wood.  This is a double wedge -- two wedges put together.
Sometimes splitting wood with an axe is not quite enough.  A splitting wedge can be placed on the upended wood and a sledge hammer used to force the wedge into the wood.
Here is how one man used a tire to help him!  Click over to about 3:00 minutes.

My husband who likes to play golf uses a pitching wedge.
You can also wedge open a door with a door wedge.

Some wedges are not used as a simple machine:
You girls may sometimes wear wedge shoes.
You might eat a wedge of cheese or a salad wedge.
If you want to sit between your two best friends, you can wedge in between them.  This can be very useful, but I would not call it a simple machine.  =)


(7) p. 102-105, The Screw

Formula for finding the Mechanical Advantage of a Screw:
First find the Circumference of the screwdriver or device turning the screw:
1.  Circumference = 3.1416 x (diameter) [note: this is the only multiplication in the formulas in this module.]

Plug the circumference into your MA formula:
2.  MA = (circumference) ÷ (pitch)  "Pitch" is the distance between threads on the screw.


  1. My children and I love your information. It makes their science class so much fun. Thank you so much for sharing!
    :) Vicki

  2. Thanks, Vicki! Glad it makes your science fun.
    Glad to share. =)

  3. Thank you Marty,
    We are loving your blog. It is just the extra boost we needed. My daughter likes the videos, flashcards, etc. She is a very visual learner and loves science so the two go hand-in-hand very well.

  4. You're welcome! =)
    I love videos.

  5. Replies
    1. Apologia's textbooks have a study guide at the end of each chapter.
      It's basically a chapter review, but called a study guide because it's a guide of what types of things in the module you need to study for the test.

  6. This is the most wonderful science videos for school, but sometimes i run into copyright removed videos and i cannot watch them. and some are removed, but still this site is worth the time i spent on it.

    1. Thank you. Yes, I know what you mean about removed videos. =( It leaves me stuck with trying to remember exactly what videos I had put in a particular post, sometimes three or four years ago! =( I would love to find replacement videos, but it is hard to keep up with that many posts. I keep wanting to go back and go over them all. Maybe someday. =)


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